Bathing in Sunshine<\/h1>\r\n<\/div>\r\nSummer sun may feel good on your body, but its invisible [pb_glossary id=\"3537\"]UV rays[\/pb_glossary] wreak havoc on your skin. Exposing the skin to UV light causes photo-aging: premature wrinkling, brown discolourations, and other unattractive signs of sun exposure. Even worse, UV light increases your risk of skin cancer.\r\n\r\nWhat Is Skin Cancer?<\/h1>\r\n<\/div>\r\nSkin [pb_glossary id=\"5605\"]cancer[\/pb_glossary] is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to UV light, which damages [pb_glossary id=\"277\"]DNA[\/pb_glossary]. Therefore, skin cancer most often develops on areas of the skin that are frequently exposed to UV light. However, it can also occur on areas that are rarely exposed to UV light. Skin cancer affects people of all skin colours, including those with dark skin. It also affects more people altogether than all other cancers combined. One in five Canadians develops skin cancer in his or her lifetime.\r\n\r\nTypes of Skin Cancer<\/h1>\r\n<\/div>\r\nSkin cancer begins in the outer layer of skin, the\u00a0[pb_glossary id=\"5991\"]epidermis[\/pb_glossary]. There are three common types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma.\r\nBasal Cell Carcinoma<\/h2>\r\n[caption id=\"attachment_3930\" align=\"alignright\" width=\"382\"]![\"10.6](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Basal_cell_carcinoma_ulcerated-2.jpg\")
Figure 10.7.2 Basal cell carcinoma[\/caption]\r\n\r\n[pb_glossary id=\"3927\"]Basal cell carcinoma[\/pb_glossary]<\/strong> occurs in basal cells of the epidermis. Basal cells are [pb_glossary id=\"3163\"]stem cells<\/span>[\/pb_glossary]<\/span> in the [pb_glossary id=\"3542\"]stratum basale[\/pb_glossary] layer that divide to form all the keratinocytes of the epidermis. Basal cell carcinoma is the most common form of skin cancer and 1 in 8 Canadians will develop basal cell carcinoma during their lifetime.\u00a0 A basal cell carcinoma may appear as a pearly or waxy sore, like the one shown in Figure 10.7.2. Basal cell carcinomas rarely spread (or undergo <\/span>[pb_glossary id=\"3928\"]metastasis[\/pb_glossary]<\/strong>)<\/span>,<\/strong>\u00a0so they can generally be cured with a\u00a0<\/span>[pb_glossary id=\"3929\"]biopsy[\/pb_glossary],<\/strong>\u00a0in which the lesion is cut out of the skin and analyzed in a medical lab.<\/span>\r\n\r\n\r\nSquamous Cell Carcinoma<\/span>\r\n\r\n<\/div>\r\n\r\n[caption id=\"attachment_3932\" align=\"alignleft\" width=\"192\"]![\"10.7](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Squamous_cell_carcinoma_1-2.jpg\")
Figure 10.7.3 Squamous cell carcinoma[\/caption]\r\n\r\n[pb_glossary id=\"3931\"]Squamous cell carcinoma[\/pb_glossary]<\/strong> occurs in squamous cells of the epidermis. Squamous cells are flattened, [pb_glossary id=\"3525\"]keratin[\/pb_glossary]-filled cells in upper layers of the epidermis. Squamous cell carcinoma is the second most common form of skin cancer. More than two million cases occur in the United States each year. A squamous cell carcinoma may appear as a firm, red nodule, or as a flat lesion with a scaly or crusty surface, like the one pictured in Figure 10.7.3. Squamous cell carcinomas are generally localized and unlikely to metastasize, so they are usually curable surgically.\r\n\r\n \r\n\r\n\r\nMelanoma<\/span>\r\n\r\n<\/div>\r\n\r\n[caption id=\"attachment_3934\" align=\"alignleft\" width=\"251\"]![\"10.7](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Melanoma-2.jpg\")
Figure 10.7.4 Melanoma[\/caption]\r\n\r\n[pb_glossary id=\"3933\"]Melanoma[\/pb_glossary]<\/strong> occurs in [pb_glossary id=\"3526\"]melanocytes[\/pb_glossary] of the epidermis. Melanocytes are the melanin-producing cells in the stratum basale of the epidermis. Melanoma is the rarest type of skin cancer, accounting for less than one per cent of all skin cancer cases. Melanoma, however, is the most deadly type of skin cancer. It causes the vast majority of skin cancer deaths, because melanoma is malignant. If not treated, it will metastasize and spread to other parts of the body. If melanoma is detected early and while it is still localized in the skin, most patients survive for at least five years. If melanoma is discovered only after it has already metastasized to distant organs, there is only a 17% of patients surviving for five years. You can see an example of a melanoma in Figure 10.7.4.\r\n\r\nMelanoma can develop anywhere on the body. It may develop in otherwise normal skin, or an existing mole may become cancerous. Signs of melanoma may include a:\r\n\r\n \t- Mole that changes in size, feel, or colour.<\/li>\r\n \t
- Mole that bleeds.<\/li>\r\n \t
- Large brown spot on the skin sprinkled with darker specks.<\/li>\r\n \t
- Small lesion with an irregular border and parts that appear red, white, blue, or blue-black.<\/li>\r\n \t
- Dark lesion on the palms, soles, fingertips, toes, or mucous membranes.<\/li>\r\n<\/ul>\r\n\r\n
Skin Cancer Risk Factors<\/h1>\r\n<\/div>\r\nExposure to UV radiation causes about 90 per cent of all skin cancer cases. The connection between skin cancer and UV light is so strong that the World Health Organization has classified UV radiation (whether from tanning beds or the sun) as a Group 1 carcinogen (cancer-causing agent). Group 1 carcinogens are those carcinogens that are known with virtual certainty<\/em>\u00a0to cause\u00a0cancer. In addition to UV light,\u00a0Group 1 carcinogens\u00a0include tobacco and plutonium.\u00a0In terms of numbers of cancers caused, UV radiation is far worse than tobacco. More people develop skin cancer because of UV light exposure than develop lung\u00a0cancer\u00a0because of smoking. The increase in cancer risk due to UV light is especially great if you have ever had blistering sunburns as a child or teen.\r\n\r\nBesides UV light exposure, other risk factors for skin cancer include:\r\n\r\n \t- Having light coloured skin.<\/li>\r\n \t
- Having a lot of moles.<\/li>\r\n \t
- Being diagnosed with precancerous skin lesions.<\/li>\r\n \t
- Having a family history of skin cancer.<\/li>\r\n \t
- Having a personal history of skin cancer.<\/li>\r\n \t
- Having a weakened immune system.<\/li>\r\n \t
- Being exposed to other forms of radiation or to certain toxic substances such as arsenic.<\/li>\r\n<\/ul>\r\n\r\n
Feature: My\u00a0Human Body<\/h1>\r\n<\/div>\r\nAs with most types of cancer, skin cancer is easiest to treat and most likely to be cured the earlier it is detected. The skin is one of the few organs that you can monitor for cancer yourself, as long as you know what to look for. A brown spot on the skin is likely to be a harmless mole, but it could be a sign of skin cancer. As shown in Figure 10.7.5 below, unlike moles, skin cancers may be asymmetrical, have irregular borders, may be very dark in colour, and may have a relatively great diameter. These characteristics can be remembered with the acronym ABCD.\r\n\r\n\r\n[caption id=\"attachment_3935\" align=\"aligncenter\" width=\"500\"]![\"10.7](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/ABCDs-of-skin-cancer-2.png\")
Figure 10.7.5 ABCDs of skin cancer[\/caption]\r\n\r\n<\/div>\r\nWith the help of\u00a0mirrors, you should check all of your skin regularly. Look for new skin growths or changes in any existing moles, freckles, bumps, or birthmarks. Report anything suspicious or different to your doctor.\r\n\r\nIf you have risk factors for skin cancer, it\u2019s a good idea to have an annual skin check by a dermatologist. This helps ensure that cancerous or precancerous lesions will be detected before they grow too large and become difficult to cure, or in the case of melanoma, before they metastasize.\r\n\r\n10.7 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Skin [pb_glossary id=\"5605\"]cancer[\/pb_glossary] is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to [pb_glossary id=\"3537\"]UV light[\/pb_glossary], which damages [pb_glossary id=\"277\"]DNA[\/pb_glossary]. Skin cancer affects more Canadians than all other cancers combined. There are three common types of skin cancer: [pb_glossary id=\"3927\"]basal cell carcinoma[\/pb_glossary], [pb_glossary id=\"3931\"]squamous cell carcinoma[\/pb_glossary], and [pb_glossary id=\"3933\"]melanoma[\/pb_glossary]. Carcinomas are more common and unlikely to metastasize. Melanoma is rare and likely to metastasize. It causes most skin cancer deaths.<\/li>\r\n \t
- Besides exposure to UV light, risk factors for skin cancer include having light coloured skin, having lots of moles, and a family history of skin cancer, among several others.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n10.7 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is skin cancer?<\/li>\r\n \t
- How common is skin cancer?<\/li>\r\n \t
- [h5p id=\"589\"]<\/li>\r\n \t
- Compare and contrast the three common types of skin cancer.<\/li>\r\n \t
- Identify factors that increase the risk of skin cancer.<\/li>\r\n \t
- How does exposure to UV light cause skin cancer?<\/li>\r\n \t
- In which layer of the skin does skin cancer normally start?<\/li>\r\n \t
- Which two skin cancers described in this section start in the same sub-layer? Include the name of the sub-layer and the cells affected in each of these cancers.<\/li>\r\n \t
- Which type of skin cancer is most likely to spread to other organs? Explain your answer.<\/li>\r\n \t
- Which form of skin cancer is the most deadly?<\/li>\r\n \t
- What are some ways people can reduce their risk of getting skin cancer? Explain your answer.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n10.7 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=60e-t4zglBk&feature=emb_logo\r\nThe skin 'beauty' and the sun 'beast': Charareh Pourzand at TEDxBathUniveristy, TEDx Talks, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=ID-O-Ion3EQ&feature=emb_logo\r\n
Cancer of the Vulva, Robert Miller, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w\r\n
How do cancer cells behave differently from healthy ones? - George Zaidan, TED-Ed, 2012.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n
Attributions<\/h2>\r\nFigure 10.7.1<\/strong>\r\n\r\nStolen_Moment_in_the_Sun<\/a> by Angie Garrett<\/a> on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 10.7.2<\/strong>\r\n\r\nBasal_cell_carcinoma,_ulcerated<\/a> by Kelly Nelson (Photographer) from National Cancer Institute<\/a> (part of the National Institutes of Health)<\/a> with the ID\u00a09237<\/a> on Wikimedia Commons was released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/b>\r\n\r\nFigure 10.7.3<\/strong>\r\n\r\nSquamous_cell_carcinoma_(1)<\/a> by Kelly Nelson (Photographer) from National Cancer Institute<\/a> (part of the National Institutes of Health)<\/a> with the ID\u00a09248<\/a> on Wikimedia Commons was released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/b>\r\n\r\nFigure 10.7.4<\/strong>\r\n\r\nMelanoma<\/a> by Unknown author\u00a0(Photographer) from National Cancer Institute<\/a> (part of the National Institutes of Health)<\/a> with the AV-8500-3850\/ ID 9186<\/a> on Wikimedia Commons was released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/b>\r\n\r\n\r\nFigure 10.7.5<\/strong>\r\n\r\nABCDs of skin cancer<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license. (Original images courtesy of NCI: ID numbers 2362;<\/a> 2363<\/a>; 2364;<\/a> and 2184<\/a>)\r\n![\"\"](\"https:\/\/www.ck12info.org\/wp-content\/uploads\/2016\/05\/logo_ck12.png\")
\u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span>![\"CK-12](\"https:\/\/www.ck12info.org\/wp-content\/uploads\/2016\/05\/icon_licence.png\" "\\"CK-12")
<\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\r\nReferences<\/h2>\r\n
Brainard, J\/ CK-12 Foundation. (2016). Figure 5 ABCDs of skin cancer[digital image]. In CK-12 College Human Biology<\/em> (Section 12.7) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/12.7\/<\/p>\r\nPublic Health Agency of Canada. (2019, December 9). Non melanoma skin cancer. Canada.ca. https:\/\/www.canada.ca\/en\/public-health\/services\/chronic-diseases\/cancer\/non-melanoma-skin-cancer.html<\/a><\/p>\r\nRobert Miller. (2014, July 22). Cancer of the vulva. YouTube. https:\/\/www.youtube.com\/watch?v=ID-O-Ion3EQ<\/p>\r\n
TED-Ed. (2012, December 5). How do cancer cells behave differently from healthy ones? - George Zaidan. YouTube. https:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w<\/p>\r\n
TEDx Talks. (2014, March 28). The skin 'beauty' and the sun 'beast': Charareh Pourzand at TEDxBathUniveristy. YouTube. https:\/\/www.youtube.com\/watch?v=60e-t4zglBk<\/p>","rendered":"
<\/p>\n![\"10.7.1](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2019\/06\/Stolen_Moment_in_the_Sun-2.jpg\")
Figure 10.7.1 I hope they’re wearing sunscreen!<\/em><\/figcaption><\/figure>\n\nBathing in Sunshine<\/h1>\n<\/div>\n
Summer sun may feel good on your body, but its invisible UV rays<\/a> wreak havoc on your skin. Exposing the skin to UV light causes photo-aging: premature wrinkling, brown discolourations, and other unattractive signs of sun exposure. Even worse, UV light increases your risk of skin cancer.<\/p>\n\nWhat Is Skin Cancer?<\/h1>\n<\/div>\n
Skin cancer<\/a> is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to UV light, which damages DNA<\/a>. Therefore, skin cancer most often develops on areas of the skin that are frequently exposed to UV light. However, it can also occur on areas that are rarely exposed to UV light. Skin cancer affects people of all skin colours, including those with dark skin. It also affects more people altogether than all other cancers combined. One in five Canadians develops skin cancer in his or her lifetime.<\/p>\n\nTypes of Skin Cancer<\/h1>\n<\/div>\n
Skin cancer begins in the outer layer of skin, the\u00a0epidermis<\/a>. There are three common types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma.<\/p>\nBasal Cell Carcinoma<\/h2>\nFigure 10.7.2 Basal cell carcinoma<\/figcaption><\/figure>\nBasal cell carcinoma<\/a><\/strong> occurs in basal cells of the epidermis. Basal cells are stem cells<\/span><\/a><\/span> in the stratum basale<\/a> layer that divide to form all the keratinocytes of the epidermis. Basal cell carcinoma is the most common form of skin cancer and 1 in 8 Canadians will develop basal cell carcinoma during their lifetime.\u00a0 A basal cell carcinoma may appear as a pearly or waxy sore, like the one shown in Figure 10.7.2. Basal cell carcinomas rarely spread (or undergo <\/span>metastasis<\/a><\/strong>)<\/span>,<\/strong>\u00a0so they can generally be cured with a\u00a0<\/span>biopsy<\/a>,<\/strong>\u00a0in which the lesion is cut out of the skin and analyzed in a medical lab.<\/span><\/p>\n\nSquamous Cell Carcinoma<\/span><\/p>\n<\/div>\nFigure 10.7.3 Squamous cell carcinoma<\/figcaption><\/figure>\nSquamous cell carcinoma<\/a><\/strong> occurs in squamous cells of the epidermis. Squamous cells are flattened, keratin<\/a>-filled cells in upper layers of the epidermis. Squamous cell carcinoma is the second most common form of skin cancer. More than two million cases occur in the United States each year. A squamous cell carcinoma may appear as a firm, red nodule, or as a flat lesion with a scaly or crusty surface, like the one pictured in Figure 10.7.3. Squamous cell carcinomas are generally localized and unlikely to metastasize, so they are usually curable surgically.<\/p>\n <\/p>\n
\nMelanoma<\/span><\/p>\n<\/div>\nFigure 10.7.4 Melanoma<\/figcaption><\/figure>\nMelanoma<\/a><\/strong> occurs in melanocytes<\/a> of the epidermis. Melanocytes are the melanin-producing cells in the stratum basale of the epidermis. Melanoma is the rarest type of skin cancer, accounting for less than one per cent of all skin cancer cases. Melanoma, however, is the most deadly type of skin cancer. It causes the vast majority of skin cancer deaths, because melanoma is malignant. If not treated, it will metastasize and spread to other parts of the body. If melanoma is detected early and while it is still localized in the skin, most patients survive for at least five years. If melanoma is discovered only after it has already metastasized to distant organs, there is only a 17% of patients surviving for five years. You can see an example of a melanoma in Figure 10.7.4.<\/p>\nMelanoma can develop anywhere on the body. It may develop in otherwise normal skin, or an existing mole may become cancerous. Signs of melanoma may include a:<\/p>\n
\n- Mole that changes in size, feel, or colour.<\/li>\n
- Mole that bleeds.<\/li>\n
- Large brown spot on the skin sprinkled with darker specks.<\/li>\n
- Small lesion with an irregular border and parts that appear red, white, blue, or blue-black.<\/li>\n
- Dark lesion on the palms, soles, fingertips, toes, or mucous membranes.<\/li>\n<\/ul>\n\n
Skin Cancer Risk Factors<\/h1>\n<\/div>\n
Exposure to UV radiation causes about 90 per cent of all skin cancer cases. The connection between skin cancer and UV light is so strong that the World Health Organization has classified UV radiation (whether from tanning beds or the sun) as a Group 1 carcinogen (cancer-causing agent). Group 1 carcinogens are those carcinogens that are known with virtual certainty<\/em>\u00a0to cause\u00a0cancer. In addition to UV light,\u00a0Group 1 carcinogens\u00a0include tobacco and plutonium.\u00a0In terms of numbers of cancers caused, UV radiation is far worse than tobacco. More people develop skin cancer because of UV light exposure than develop lung\u00a0cancer\u00a0because of smoking. The increase in cancer risk due to UV light is especially great if you have ever had blistering sunburns as a child or teen.<\/p>\nBesides UV light exposure, other risk factors for skin cancer include:<\/p>\n
\n- Having light coloured skin.<\/li>\n
- Having a lot of moles.<\/li>\n
- Being diagnosed with precancerous skin lesions.<\/li>\n
- Having a family history of skin cancer.<\/li>\n
- Having a personal history of skin cancer.<\/li>\n
- Having a weakened immune system.<\/li>\n
- Being exposed to other forms of radiation or to certain toxic substances such as arsenic.<\/li>\n<\/ul>\n\n
Feature: My\u00a0Human Body<\/h1>\n<\/div>\n
As with most types of cancer, skin cancer is easiest to treat and most likely to be cured the earlier it is detected. The skin is one of the few organs that you can monitor for cancer yourself, as long as you know what to look for. A brown spot on the skin is likely to be a harmless mole, but it could be a sign of skin cancer. As shown in Figure 10.7.5 below, unlike moles, skin cancers may be asymmetrical, have irregular borders, may be very dark in colour, and may have a relatively great diameter. These characteristics can be remembered with the acronym ABCD.<\/p>\n
\nFigure 10.7.5 ABCDs of skin cancer<\/figcaption><\/figure>\n<\/div>\nWith the help of\u00a0mirrors, you should check all of your skin regularly. Look for new skin growths or changes in any existing moles, freckles, bumps, or birthmarks. Report anything suspicious or different to your doctor.<\/p>\n
If you have risk factors for skin cancer, it\u2019s a good idea to have an annual skin check by a dermatologist. This helps ensure that cancerous or precancerous lesions will be detected before they grow too large and become difficult to cure, or in the case of melanoma, before they metastasize.<\/p>\n
\n\n10.7 Summary<\/span><\/h1>\n<\/header>\n\n\n- Skin cancer<\/a> is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to UV light<\/a>, which damages DNA<\/a>. Skin cancer affects more Canadians than all other cancers combined. There are three common types of skin cancer: basal cell carcinoma<\/a>, squamous cell carcinoma<\/a>, and melanoma<\/a>. Carcinomas are more common and unlikely to metastasize. Melanoma is rare and likely to metastasize. It causes most skin cancer deaths.<\/li>\n
- Besides exposure to UV light, risk factors for skin cancer include having light coloured skin, having lots of moles, and a family history of skin cancer, among several others.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n10.7 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- What is skin cancer?<\/li>\n
- How common is skin cancer?<\/li>\n
- \n\n
What Is Skin Cancer?<\/h1>\r\n<\/div>\r\nSkin [pb_glossary id=\"5605\"]cancer[\/pb_glossary] is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to UV light, which damages [pb_glossary id=\"277\"]DNA[\/pb_glossary]. Therefore, skin cancer most often develops on areas of the skin that are frequently exposed to UV light. However, it can also occur on areas that are rarely exposed to UV light. Skin cancer affects people of all skin colours, including those with dark skin. It also affects more people altogether than all other cancers combined. One in five Canadians develops skin cancer in his or her lifetime.\r\n\r\nTypes of Skin Cancer<\/h1>\r\n<\/div>\r\nSkin cancer begins in the outer layer of skin, the\u00a0[pb_glossary id=\"5991\"]epidermis[\/pb_glossary]. There are three common types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma.\r\nBasal Cell Carcinoma<\/h2>\r\n[caption id=\"attachment_3930\" align=\"alignright\" width=\"382\"] Figure 10.7.2 Basal cell carcinoma[\/caption]\r\n\r\n[pb_glossary id=\"3927\"]Basal cell carcinoma[\/pb_glossary]<\/strong> occurs in basal cells of the epidermis. Basal cells are [pb_glossary id=\"3163\"]stem cells<\/span>[\/pb_glossary]<\/span> in the [pb_glossary id=\"3542\"]stratum basale[\/pb_glossary] layer that divide to form all the keratinocytes of the epidermis. Basal cell carcinoma is the most common form of skin cancer and 1 in 8 Canadians will develop basal cell carcinoma during their lifetime.\u00a0 A basal cell carcinoma may appear as a pearly or waxy sore, like the one shown in Figure 10.7.2. Basal cell carcinomas rarely spread (or undergo <\/span>[pb_glossary id=\"3928\"]metastasis[\/pb_glossary]<\/strong>)<\/span>,<\/strong>\u00a0so they can generally be cured with a\u00a0<\/span>[pb_glossary id=\"3929\"]biopsy[\/pb_glossary],<\/strong>\u00a0in which the lesion is cut out of the skin and analyzed in a medical lab.<\/span>\r\n\r\n\r\nSquamous Cell Carcinoma<\/span>\r\n\r\n<\/div>\r\n\r\n[caption id=\"attachment_3932\" align=\"alignleft\" width=\"192\"] Figure 10.7.3 Squamous cell carcinoma[\/caption]\r\n\r\n[pb_glossary id=\"3931\"]Squamous cell carcinoma[\/pb_glossary]<\/strong> occurs in squamous cells of the epidermis. Squamous cells are flattened, [pb_glossary id=\"3525\"]keratin[\/pb_glossary]-filled cells in upper layers of the epidermis. Squamous cell carcinoma is the second most common form of skin cancer. More than two million cases occur in the United States each year. A squamous cell carcinoma may appear as a firm, red nodule, or as a flat lesion with a scaly or crusty surface, like the one pictured in Figure 10.7.3. Squamous cell carcinomas are generally localized and unlikely to metastasize, so they are usually curable surgically.\r\n\r\n \r\n\r\n\r\nMelanoma<\/span>\r\n\r\n<\/div>\r\n\r\n[caption id=\"attachment_3934\" align=\"alignleft\" width=\"251\"] Figure 10.7.4 Melanoma[\/caption]\r\n\r\n[pb_glossary id=\"3933\"]Melanoma[\/pb_glossary]<\/strong> occurs in [pb_glossary id=\"3526\"]melanocytes[\/pb_glossary] of the epidermis. Melanocytes are the melanin-producing cells in the stratum basale of the epidermis. Melanoma is the rarest type of skin cancer, accounting for less than one per cent of all skin cancer cases. Melanoma, however, is the most deadly type of skin cancer. It causes the vast majority of skin cancer deaths, because melanoma is malignant. If not treated, it will metastasize and spread to other parts of the body. If melanoma is detected early and while it is still localized in the skin, most patients survive for at least five years. If melanoma is discovered only after it has already metastasized to distant organs, there is only a 17% of patients surviving for five years. You can see an example of a melanoma in Figure 10.7.4.\r\n\r\nMelanoma can develop anywhere on the body. It may develop in otherwise normal skin, or an existing mole may become cancerous. Signs of melanoma may include a:\r\n\r\n \t- Mole that changes in size, feel, or colour.<\/li>\r\n \t
- Mole that bleeds.<\/li>\r\n \t
- Large brown spot on the skin sprinkled with darker specks.<\/li>\r\n \t
- Small lesion with an irregular border and parts that appear red, white, blue, or blue-black.<\/li>\r\n \t
- Dark lesion on the palms, soles, fingertips, toes, or mucous membranes.<\/li>\r\n<\/ul>\r\n\r\n
Skin Cancer Risk Factors<\/h1>\r\n<\/div>\r\nExposure to UV radiation causes about 90 per cent of all skin cancer cases. The connection between skin cancer and UV light is so strong that the World Health Organization has classified UV radiation (whether from tanning beds or the sun) as a Group 1 carcinogen (cancer-causing agent). Group 1 carcinogens are those carcinogens that are known with virtual certainty<\/em>\u00a0to cause\u00a0cancer. In addition to UV light,\u00a0Group 1 carcinogens\u00a0include tobacco and plutonium.\u00a0In terms of numbers of cancers caused, UV radiation is far worse than tobacco. More people develop skin cancer because of UV light exposure than develop lung\u00a0cancer\u00a0because of smoking. The increase in cancer risk due to UV light is especially great if you have ever had blistering sunburns as a child or teen.\r\n\r\nBesides UV light exposure, other risk factors for skin cancer include:\r\n\r\n \t- Having light coloured skin.<\/li>\r\n \t
- Having a lot of moles.<\/li>\r\n \t
- Being diagnosed with precancerous skin lesions.<\/li>\r\n \t
- Having a family history of skin cancer.<\/li>\r\n \t
- Having a personal history of skin cancer.<\/li>\r\n \t
- Having a weakened immune system.<\/li>\r\n \t
- Being exposed to other forms of radiation or to certain toxic substances such as arsenic.<\/li>\r\n<\/ul>\r\n\r\n
Feature: My\u00a0Human Body<\/h1>\r\n<\/div>\r\nAs with most types of cancer, skin cancer is easiest to treat and most likely to be cured the earlier it is detected. The skin is one of the few organs that you can monitor for cancer yourself, as long as you know what to look for. A brown spot on the skin is likely to be a harmless mole, but it could be a sign of skin cancer. As shown in Figure 10.7.5 below, unlike moles, skin cancers may be asymmetrical, have irregular borders, may be very dark in colour, and may have a relatively great diameter. These characteristics can be remembered with the acronym ABCD.\r\n\r\n\r\n[caption id=\"attachment_3935\" align=\"aligncenter\" width=\"500\"] Figure 10.7.5 ABCDs of skin cancer[\/caption]\r\n\r\n<\/div>\r\nWith the help of\u00a0mirrors, you should check all of your skin regularly. Look for new skin growths or changes in any existing moles, freckles, bumps, or birthmarks. Report anything suspicious or different to your doctor.\r\n\r\nIf you have risk factors for skin cancer, it\u2019s a good idea to have an annual skin check by a dermatologist. This helps ensure that cancerous or precancerous lesions will be detected before they grow too large and become difficult to cure, or in the case of melanoma, before they metastasize.\r\n\r\n10.7 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Skin [pb_glossary id=\"5605\"]cancer[\/pb_glossary] is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to [pb_glossary id=\"3537\"]UV light[\/pb_glossary], which damages [pb_glossary id=\"277\"]DNA[\/pb_glossary]. Skin cancer affects more Canadians than all other cancers combined. There are three common types of skin cancer: [pb_glossary id=\"3927\"]basal cell carcinoma[\/pb_glossary], [pb_glossary id=\"3931\"]squamous cell carcinoma[\/pb_glossary], and [pb_glossary id=\"3933\"]melanoma[\/pb_glossary]. Carcinomas are more common and unlikely to metastasize. Melanoma is rare and likely to metastasize. It causes most skin cancer deaths.<\/li>\r\n \t
- Besides exposure to UV light, risk factors for skin cancer include having light coloured skin, having lots of moles, and a family history of skin cancer, among several others.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n10.7 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is skin cancer?<\/li>\r\n \t
- How common is skin cancer?<\/li>\r\n \t
- [h5p id=\"589\"]<\/li>\r\n \t
- Compare and contrast the three common types of skin cancer.<\/li>\r\n \t
- Identify factors that increase the risk of skin cancer.<\/li>\r\n \t
- How does exposure to UV light cause skin cancer?<\/li>\r\n \t
- In which layer of the skin does skin cancer normally start?<\/li>\r\n \t
- Which two skin cancers described in this section start in the same sub-layer? Include the name of the sub-layer and the cells affected in each of these cancers.<\/li>\r\n \t
- Which type of skin cancer is most likely to spread to other organs? Explain your answer.<\/li>\r\n \t
- Which form of skin cancer is the most deadly?<\/li>\r\n \t
- What are some ways people can reduce their risk of getting skin cancer? Explain your answer.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n10.7 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=60e-t4zglBk&feature=emb_logo\r\nThe skin 'beauty' and the sun 'beast': Charareh Pourzand at TEDxBathUniveristy, TEDx Talks, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=ID-O-Ion3EQ&feature=emb_logo\r\n
Cancer of the Vulva, Robert Miller, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w\r\n
How do cancer cells behave differently from healthy ones? - George Zaidan, TED-Ed, 2012.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n
Attributions<\/h2>\r\nFigure 10.7.1<\/strong>\r\n\r\nStolen_Moment_in_the_Sun<\/a> by Angie Garrett<\/a> on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 10.7.2<\/strong>\r\n\r\nBasal_cell_carcinoma,_ulcerated<\/a> by Kelly Nelson (Photographer) from National Cancer Institute<\/a> (part of the National Institutes of Health)<\/a> with the ID\u00a09237<\/a> on Wikimedia Commons was released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/b>\r\n\r\nFigure 10.7.3<\/strong>\r\n\r\nSquamous_cell_carcinoma_(1)<\/a> by Kelly Nelson (Photographer) from National Cancer Institute<\/a> (part of the National Institutes of Health)<\/a> with the ID\u00a09248<\/a> on Wikimedia Commons was released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/b>\r\n\r\nFigure 10.7.4<\/strong>\r\n\r\nMelanoma<\/a> by Unknown author\u00a0(Photographer) from National Cancer Institute<\/a> (part of the National Institutes of Health)<\/a> with the AV-8500-3850\/ ID 9186<\/a> on Wikimedia Commons was released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/b>\r\n\r\n\r\nFigure 10.7.5<\/strong>\r\n\r\nABCDs of skin cancer<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license. (Original images courtesy of NCI: ID numbers 2362;<\/a> 2363<\/a>; 2364;<\/a> and 2184<\/a>)\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\r\nReferences<\/h2>\r\n
Brainard, J\/ CK-12 Foundation. (2016). Figure 5 ABCDs of skin cancer[digital image]. In CK-12 College Human Biology<\/em> (Section 12.7) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/12.7\/<\/p>\r\nPublic Health Agency of Canada. (2019, December 9). Non melanoma skin cancer. Canada.ca. https:\/\/www.canada.ca\/en\/public-health\/services\/chronic-diseases\/cancer\/non-melanoma-skin-cancer.html<\/a><\/p>\r\nRobert Miller. (2014, July 22). Cancer of the vulva. YouTube. https:\/\/www.youtube.com\/watch?v=ID-O-Ion3EQ<\/p>\r\n
TED-Ed. (2012, December 5). How do cancer cells behave differently from healthy ones? - George Zaidan. YouTube. https:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w<\/p>\r\n
TEDx Talks. (2014, March 28). The skin 'beauty' and the sun 'beast': Charareh Pourzand at TEDxBathUniveristy. YouTube. https:\/\/www.youtube.com\/watch?v=60e-t4zglBk<\/p>","rendered":"
<\/p>\nFigure 10.7.1 I hope they’re wearing sunscreen!<\/em><\/figcaption><\/figure>\n\nBathing in Sunshine<\/h1>\n<\/div>\n
Summer sun may feel good on your body, but its invisible UV rays<\/a> wreak havoc on your skin. Exposing the skin to UV light causes photo-aging: premature wrinkling, brown discolourations, and other unattractive signs of sun exposure. Even worse, UV light increases your risk of skin cancer.<\/p>\n\nWhat Is Skin Cancer?<\/h1>\n<\/div>\n
Skin cancer<\/a> is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to UV light, which damages DNA<\/a>. Therefore, skin cancer most often develops on areas of the skin that are frequently exposed to UV light. However, it can also occur on areas that are rarely exposed to UV light. Skin cancer affects people of all skin colours, including those with dark skin. It also affects more people altogether than all other cancers combined. One in five Canadians develops skin cancer in his or her lifetime.<\/p>\n\nTypes of Skin Cancer<\/h1>\n<\/div>\n
Skin cancer begins in the outer layer of skin, the\u00a0epidermis<\/a>. There are three common types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma.<\/p>\nBasal Cell Carcinoma<\/h2>\nFigure 10.7.2 Basal cell carcinoma<\/figcaption><\/figure>\nBasal cell carcinoma<\/a><\/strong> occurs in basal cells of the epidermis. Basal cells are stem cells<\/span><\/a><\/span> in the stratum basale<\/a> layer that divide to form all the keratinocytes of the epidermis. Basal cell carcinoma is the most common form of skin cancer and 1 in 8 Canadians will develop basal cell carcinoma during their lifetime.\u00a0 A basal cell carcinoma may appear as a pearly or waxy sore, like the one shown in Figure 10.7.2. Basal cell carcinomas rarely spread (or undergo <\/span>metastasis<\/a><\/strong>)<\/span>,<\/strong>\u00a0so they can generally be cured with a\u00a0<\/span>biopsy<\/a>,<\/strong>\u00a0in which the lesion is cut out of the skin and analyzed in a medical lab.<\/span><\/p>\n\nSquamous Cell Carcinoma<\/span><\/p>\n<\/div>\nFigure 10.7.3 Squamous cell carcinoma<\/figcaption><\/figure>\nSquamous cell carcinoma<\/a><\/strong> occurs in squamous cells of the epidermis. Squamous cells are flattened, keratin<\/a>-filled cells in upper layers of the epidermis. Squamous cell carcinoma is the second most common form of skin cancer. More than two million cases occur in the United States each year. A squamous cell carcinoma may appear as a firm, red nodule, or as a flat lesion with a scaly or crusty surface, like the one pictured in Figure 10.7.3. Squamous cell carcinomas are generally localized and unlikely to metastasize, so they are usually curable surgically.<\/p>\n <\/p>\n
\nMelanoma<\/span><\/p>\n<\/div>\nFigure 10.7.4 Melanoma<\/figcaption><\/figure>\nMelanoma<\/a><\/strong> occurs in melanocytes<\/a> of the epidermis. Melanocytes are the melanin-producing cells in the stratum basale of the epidermis. Melanoma is the rarest type of skin cancer, accounting for less than one per cent of all skin cancer cases. Melanoma, however, is the most deadly type of skin cancer. It causes the vast majority of skin cancer deaths, because melanoma is malignant. If not treated, it will metastasize and spread to other parts of the body. If melanoma is detected early and while it is still localized in the skin, most patients survive for at least five years. If melanoma is discovered only after it has already metastasized to distant organs, there is only a 17% of patients surviving for five years. You can see an example of a melanoma in Figure 10.7.4.<\/p>\nMelanoma can develop anywhere on the body. It may develop in otherwise normal skin, or an existing mole may become cancerous. Signs of melanoma may include a:<\/p>\n
\n- Mole that changes in size, feel, or colour.<\/li>\n
- Mole that bleeds.<\/li>\n
- Large brown spot on the skin sprinkled with darker specks.<\/li>\n
- Small lesion with an irregular border and parts that appear red, white, blue, or blue-black.<\/li>\n
- Dark lesion on the palms, soles, fingertips, toes, or mucous membranes.<\/li>\n<\/ul>\n\n
Skin Cancer Risk Factors<\/h1>\n<\/div>\n
Exposure to UV radiation causes about 90 per cent of all skin cancer cases. The connection between skin cancer and UV light is so strong that the World Health Organization has classified UV radiation (whether from tanning beds or the sun) as a Group 1 carcinogen (cancer-causing agent). Group 1 carcinogens are those carcinogens that are known with virtual certainty<\/em>\u00a0to cause\u00a0cancer. In addition to UV light,\u00a0Group 1 carcinogens\u00a0include tobacco and plutonium.\u00a0In terms of numbers of cancers caused, UV radiation is far worse than tobacco. More people develop skin cancer because of UV light exposure than develop lung\u00a0cancer\u00a0because of smoking. The increase in cancer risk due to UV light is especially great if you have ever had blistering sunburns as a child or teen.<\/p>\nBesides UV light exposure, other risk factors for skin cancer include:<\/p>\n
\n- Having light coloured skin.<\/li>\n
- Having a lot of moles.<\/li>\n
- Being diagnosed with precancerous skin lesions.<\/li>\n
- Having a family history of skin cancer.<\/li>\n
- Having a personal history of skin cancer.<\/li>\n
- Having a weakened immune system.<\/li>\n
- Being exposed to other forms of radiation or to certain toxic substances such as arsenic.<\/li>\n<\/ul>\n\n
Feature: My\u00a0Human Body<\/h1>\n<\/div>\n
As with most types of cancer, skin cancer is easiest to treat and most likely to be cured the earlier it is detected. The skin is one of the few organs that you can monitor for cancer yourself, as long as you know what to look for. A brown spot on the skin is likely to be a harmless mole, but it could be a sign of skin cancer. As shown in Figure 10.7.5 below, unlike moles, skin cancers may be asymmetrical, have irregular borders, may be very dark in colour, and may have a relatively great diameter. These characteristics can be remembered with the acronym ABCD.<\/p>\n
\nFigure 10.7.5 ABCDs of skin cancer<\/figcaption><\/figure>\n<\/div>\nWith the help of\u00a0mirrors, you should check all of your skin regularly. Look for new skin growths or changes in any existing moles, freckles, bumps, or birthmarks. Report anything suspicious or different to your doctor.<\/p>\n
If you have risk factors for skin cancer, it\u2019s a good idea to have an annual skin check by a dermatologist. This helps ensure that cancerous or precancerous lesions will be detected before they grow too large and become difficult to cure, or in the case of melanoma, before they metastasize.<\/p>\n
\n\n10.7 Summary<\/span><\/h1>\n<\/header>\n\n\n- Skin cancer<\/a> is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to UV light<\/a>, which damages DNA<\/a>. Skin cancer affects more Canadians than all other cancers combined. There are three common types of skin cancer: basal cell carcinoma<\/a>, squamous cell carcinoma<\/a>, and melanoma<\/a>. Carcinomas are more common and unlikely to metastasize. Melanoma is rare and likely to metastasize. It causes most skin cancer deaths.<\/li>\n
- Besides exposure to UV light, risk factors for skin cancer include having light coloured skin, having lots of moles, and a family history of skin cancer, among several others.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n10.7 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- What is skin cancer?<\/li>\n
- How common is skin cancer?<\/li>\n
- \n\n
Types of Skin Cancer<\/h1>\r\n<\/div>\r\nSkin cancer begins in the outer layer of skin, the\u00a0[pb_glossary id=\"5991\"]epidermis[\/pb_glossary]. There are three common types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma.\r\nBasal Cell Carcinoma<\/h2>\r\n[caption id=\"attachment_3930\" align=\"alignright\" width=\"382\"] Figure 10.7.2 Basal cell carcinoma[\/caption]\r\n\r\n[pb_glossary id=\"3927\"]Basal cell carcinoma[\/pb_glossary]<\/strong> occurs in basal cells of the epidermis. Basal cells are [pb_glossary id=\"3163\"]stem cells<\/span>[\/pb_glossary]<\/span> in the [pb_glossary id=\"3542\"]stratum basale[\/pb_glossary] layer that divide to form all the keratinocytes of the epidermis. Basal cell carcinoma is the most common form of skin cancer and 1 in 8 Canadians will develop basal cell carcinoma during their lifetime.\u00a0 A basal cell carcinoma may appear as a pearly or waxy sore, like the one shown in Figure 10.7.2. Basal cell carcinomas rarely spread (or undergo <\/span>[pb_glossary id=\"3928\"]metastasis[\/pb_glossary]<\/strong>)<\/span>,<\/strong>\u00a0so they can generally be cured with a\u00a0<\/span>[pb_glossary id=\"3929\"]biopsy[\/pb_glossary],<\/strong>\u00a0in which the lesion is cut out of the skin and analyzed in a medical lab.<\/span>\r\n\r\n\r\nSquamous Cell Carcinoma<\/span>\r\n\r\n<\/div>\r\n\r\n[caption id=\"attachment_3932\" align=\"alignleft\" width=\"192\"] Figure 10.7.3 Squamous cell carcinoma[\/caption]\r\n\r\n[pb_glossary id=\"3931\"]Squamous cell carcinoma[\/pb_glossary]<\/strong> occurs in squamous cells of the epidermis. Squamous cells are flattened, [pb_glossary id=\"3525\"]keratin[\/pb_glossary]-filled cells in upper layers of the epidermis. Squamous cell carcinoma is the second most common form of skin cancer. More than two million cases occur in the United States each year. A squamous cell carcinoma may appear as a firm, red nodule, or as a flat lesion with a scaly or crusty surface, like the one pictured in Figure 10.7.3. Squamous cell carcinomas are generally localized and unlikely to metastasize, so they are usually curable surgically.\r\n\r\n \r\n\r\n\r\nMelanoma<\/span>\r\n\r\n<\/div>\r\n\r\n[caption id=\"attachment_3934\" align=\"alignleft\" width=\"251\"] Figure 10.7.4 Melanoma[\/caption]\r\n\r\n[pb_glossary id=\"3933\"]Melanoma[\/pb_glossary]<\/strong> occurs in [pb_glossary id=\"3526\"]melanocytes[\/pb_glossary] of the epidermis. Melanocytes are the melanin-producing cells in the stratum basale of the epidermis. Melanoma is the rarest type of skin cancer, accounting for less than one per cent of all skin cancer cases. Melanoma, however, is the most deadly type of skin cancer. It causes the vast majority of skin cancer deaths, because melanoma is malignant. If not treated, it will metastasize and spread to other parts of the body. If melanoma is detected early and while it is still localized in the skin, most patients survive for at least five years. If melanoma is discovered only after it has already metastasized to distant organs, there is only a 17% of patients surviving for five years. You can see an example of a melanoma in Figure 10.7.4.\r\n\r\nMelanoma can develop anywhere on the body. It may develop in otherwise normal skin, or an existing mole may become cancerous. Signs of melanoma may include a:\r\n\r\n \t- Mole that changes in size, feel, or colour.<\/li>\r\n \t
- Mole that bleeds.<\/li>\r\n \t
- Large brown spot on the skin sprinkled with darker specks.<\/li>\r\n \t
- Small lesion with an irregular border and parts that appear red, white, blue, or blue-black.<\/li>\r\n \t
- Dark lesion on the palms, soles, fingertips, toes, or mucous membranes.<\/li>\r\n<\/ul>\r\n\r\n
Skin Cancer Risk Factors<\/h1>\r\n<\/div>\r\nExposure to UV radiation causes about 90 per cent of all skin cancer cases. The connection between skin cancer and UV light is so strong that the World Health Organization has classified UV radiation (whether from tanning beds or the sun) as a Group 1 carcinogen (cancer-causing agent). Group 1 carcinogens are those carcinogens that are known with virtual certainty<\/em>\u00a0to cause\u00a0cancer. In addition to UV light,\u00a0Group 1 carcinogens\u00a0include tobacco and plutonium.\u00a0In terms of numbers of cancers caused, UV radiation is far worse than tobacco. More people develop skin cancer because of UV light exposure than develop lung\u00a0cancer\u00a0because of smoking. The increase in cancer risk due to UV light is especially great if you have ever had blistering sunburns as a child or teen.\r\n\r\nBesides UV light exposure, other risk factors for skin cancer include:\r\n\r\n \t- Having light coloured skin.<\/li>\r\n \t
- Having a lot of moles.<\/li>\r\n \t
- Being diagnosed with precancerous skin lesions.<\/li>\r\n \t
- Having a family history of skin cancer.<\/li>\r\n \t
- Having a personal history of skin cancer.<\/li>\r\n \t
- Having a weakened immune system.<\/li>\r\n \t
- Being exposed to other forms of radiation or to certain toxic substances such as arsenic.<\/li>\r\n<\/ul>\r\n\r\n
Feature: My\u00a0Human Body<\/h1>\r\n<\/div>\r\nAs with most types of cancer, skin cancer is easiest to treat and most likely to be cured the earlier it is detected. The skin is one of the few organs that you can monitor for cancer yourself, as long as you know what to look for. A brown spot on the skin is likely to be a harmless mole, but it could be a sign of skin cancer. As shown in Figure 10.7.5 below, unlike moles, skin cancers may be asymmetrical, have irregular borders, may be very dark in colour, and may have a relatively great diameter. These characteristics can be remembered with the acronym ABCD.\r\n\r\n\r\n[caption id=\"attachment_3935\" align=\"aligncenter\" width=\"500\"] Figure 10.7.5 ABCDs of skin cancer[\/caption]\r\n\r\n<\/div>\r\nWith the help of\u00a0mirrors, you should check all of your skin regularly. Look for new skin growths or changes in any existing moles, freckles, bumps, or birthmarks. Report anything suspicious or different to your doctor.\r\n\r\nIf you have risk factors for skin cancer, it\u2019s a good idea to have an annual skin check by a dermatologist. This helps ensure that cancerous or precancerous lesions will be detected before they grow too large and become difficult to cure, or in the case of melanoma, before they metastasize.\r\n\r\n10.7 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Skin [pb_glossary id=\"5605\"]cancer[\/pb_glossary] is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to [pb_glossary id=\"3537\"]UV light[\/pb_glossary], which damages [pb_glossary id=\"277\"]DNA[\/pb_glossary]. Skin cancer affects more Canadians than all other cancers combined. There are three common types of skin cancer: [pb_glossary id=\"3927\"]basal cell carcinoma[\/pb_glossary], [pb_glossary id=\"3931\"]squamous cell carcinoma[\/pb_glossary], and [pb_glossary id=\"3933\"]melanoma[\/pb_glossary]. Carcinomas are more common and unlikely to metastasize. Melanoma is rare and likely to metastasize. It causes most skin cancer deaths.<\/li>\r\n \t
- Besides exposure to UV light, risk factors for skin cancer include having light coloured skin, having lots of moles, and a family history of skin cancer, among several others.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n10.7 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is skin cancer?<\/li>\r\n \t
- How common is skin cancer?<\/li>\r\n \t
- [h5p id=\"589\"]<\/li>\r\n \t
- Compare and contrast the three common types of skin cancer.<\/li>\r\n \t
- Identify factors that increase the risk of skin cancer.<\/li>\r\n \t
- How does exposure to UV light cause skin cancer?<\/li>\r\n \t
- In which layer of the skin does skin cancer normally start?<\/li>\r\n \t
- Which two skin cancers described in this section start in the same sub-layer? Include the name of the sub-layer and the cells affected in each of these cancers.<\/li>\r\n \t
- Which type of skin cancer is most likely to spread to other organs? Explain your answer.<\/li>\r\n \t
- Which form of skin cancer is the most deadly?<\/li>\r\n \t
- What are some ways people can reduce their risk of getting skin cancer? Explain your answer.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n10.7 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=60e-t4zglBk&feature=emb_logo\r\nThe skin 'beauty' and the sun 'beast': Charareh Pourzand at TEDxBathUniveristy, TEDx Talks, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=ID-O-Ion3EQ&feature=emb_logo\r\n
Cancer of the Vulva, Robert Miller, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w\r\n
How do cancer cells behave differently from healthy ones? - George Zaidan, TED-Ed, 2012.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n
Attributions<\/h2>\r\nFigure 10.7.1<\/strong>\r\n\r\nStolen_Moment_in_the_Sun<\/a> by Angie Garrett<\/a> on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 10.7.2<\/strong>\r\n\r\nBasal_cell_carcinoma,_ulcerated<\/a> by Kelly Nelson (Photographer) from National Cancer Institute<\/a> (part of the National Institutes of Health)<\/a> with the ID\u00a09237<\/a> on Wikimedia Commons was released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/b>\r\n\r\nFigure 10.7.3<\/strong>\r\n\r\nSquamous_cell_carcinoma_(1)<\/a> by Kelly Nelson (Photographer) from National Cancer Institute<\/a> (part of the National Institutes of Health)<\/a> with the ID\u00a09248<\/a> on Wikimedia Commons was released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/b>\r\n\r\nFigure 10.7.4<\/strong>\r\n\r\nMelanoma<\/a> by Unknown author\u00a0(Photographer) from National Cancer Institute<\/a> (part of the National Institutes of Health)<\/a> with the AV-8500-3850\/ ID 9186<\/a> on Wikimedia Commons was released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/b>\r\n\r\n\r\nFigure 10.7.5<\/strong>\r\n\r\nABCDs of skin cancer<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license. (Original images courtesy of NCI: ID numbers 2362;<\/a> 2363<\/a>; 2364;<\/a> and 2184<\/a>)\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\r\nReferences<\/h2>\r\n
Brainard, J\/ CK-12 Foundation. (2016). Figure 5 ABCDs of skin cancer[digital image]. In CK-12 College Human Biology<\/em> (Section 12.7) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/12.7\/<\/p>\r\nPublic Health Agency of Canada. (2019, December 9). Non melanoma skin cancer. Canada.ca. https:\/\/www.canada.ca\/en\/public-health\/services\/chronic-diseases\/cancer\/non-melanoma-skin-cancer.html<\/a><\/p>\r\nRobert Miller. (2014, July 22). Cancer of the vulva. YouTube. https:\/\/www.youtube.com\/watch?v=ID-O-Ion3EQ<\/p>\r\n
TED-Ed. (2012, December 5). How do cancer cells behave differently from healthy ones? - George Zaidan. YouTube. https:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w<\/p>\r\n
TEDx Talks. (2014, March 28). The skin 'beauty' and the sun 'beast': Charareh Pourzand at TEDxBathUniveristy. YouTube. https:\/\/www.youtube.com\/watch?v=60e-t4zglBk<\/p>","rendered":"
<\/p>\nFigure 10.7.1 I hope they’re wearing sunscreen!<\/em><\/figcaption><\/figure>\n\nBathing in Sunshine<\/h1>\n<\/div>\n
Summer sun may feel good on your body, but its invisible UV rays<\/a> wreak havoc on your skin. Exposing the skin to UV light causes photo-aging: premature wrinkling, brown discolourations, and other unattractive signs of sun exposure. Even worse, UV light increases your risk of skin cancer.<\/p>\n\nWhat Is Skin Cancer?<\/h1>\n<\/div>\n
Skin cancer<\/a> is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to UV light, which damages DNA<\/a>. Therefore, skin cancer most often develops on areas of the skin that are frequently exposed to UV light. However, it can also occur on areas that are rarely exposed to UV light. Skin cancer affects people of all skin colours, including those with dark skin. It also affects more people altogether than all other cancers combined. One in five Canadians develops skin cancer in his or her lifetime.<\/p>\n\nTypes of Skin Cancer<\/h1>\n<\/div>\n
Skin cancer begins in the outer layer of skin, the\u00a0epidermis<\/a>. There are three common types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma.<\/p>\nBasal Cell Carcinoma<\/h2>\nFigure 10.7.2 Basal cell carcinoma<\/figcaption><\/figure>\nBasal cell carcinoma<\/a><\/strong> occurs in basal cells of the epidermis. Basal cells are stem cells<\/span><\/a><\/span> in the stratum basale<\/a> layer that divide to form all the keratinocytes of the epidermis. Basal cell carcinoma is the most common form of skin cancer and 1 in 8 Canadians will develop basal cell carcinoma during their lifetime.\u00a0 A basal cell carcinoma may appear as a pearly or waxy sore, like the one shown in Figure 10.7.2. Basal cell carcinomas rarely spread (or undergo <\/span>metastasis<\/a><\/strong>)<\/span>,<\/strong>\u00a0so they can generally be cured with a\u00a0<\/span>biopsy<\/a>,<\/strong>\u00a0in which the lesion is cut out of the skin and analyzed in a medical lab.<\/span><\/p>\n\nSquamous Cell Carcinoma<\/span><\/p>\n<\/div>\nFigure 10.7.3 Squamous cell carcinoma<\/figcaption><\/figure>\nSquamous cell carcinoma<\/a><\/strong> occurs in squamous cells of the epidermis. Squamous cells are flattened, keratin<\/a>-filled cells in upper layers of the epidermis. Squamous cell carcinoma is the second most common form of skin cancer. More than two million cases occur in the United States each year. A squamous cell carcinoma may appear as a firm, red nodule, or as a flat lesion with a scaly or crusty surface, like the one pictured in Figure 10.7.3. Squamous cell carcinomas are generally localized and unlikely to metastasize, so they are usually curable surgically.<\/p>\n <\/p>\n
\nMelanoma<\/span><\/p>\n<\/div>\nFigure 10.7.4 Melanoma<\/figcaption><\/figure>\nMelanoma<\/a><\/strong> occurs in melanocytes<\/a> of the epidermis. Melanocytes are the melanin-producing cells in the stratum basale of the epidermis. Melanoma is the rarest type of skin cancer, accounting for less than one per cent of all skin cancer cases. Melanoma, however, is the most deadly type of skin cancer. It causes the vast majority of skin cancer deaths, because melanoma is malignant. If not treated, it will metastasize and spread to other parts of the body. If melanoma is detected early and while it is still localized in the skin, most patients survive for at least five years. If melanoma is discovered only after it has already metastasized to distant organs, there is only a 17% of patients surviving for five years. You can see an example of a melanoma in Figure 10.7.4.<\/p>\nMelanoma can develop anywhere on the body. It may develop in otherwise normal skin, or an existing mole may become cancerous. Signs of melanoma may include a:<\/p>\n
\n- Mole that changes in size, feel, or colour.<\/li>\n
- Mole that bleeds.<\/li>\n
- Large brown spot on the skin sprinkled with darker specks.<\/li>\n
- Small lesion with an irregular border and parts that appear red, white, blue, or blue-black.<\/li>\n
- Dark lesion on the palms, soles, fingertips, toes, or mucous membranes.<\/li>\n<\/ul>\n\n
Skin Cancer Risk Factors<\/h1>\n<\/div>\n
Exposure to UV radiation causes about 90 per cent of all skin cancer cases. The connection between skin cancer and UV light is so strong that the World Health Organization has classified UV radiation (whether from tanning beds or the sun) as a Group 1 carcinogen (cancer-causing agent). Group 1 carcinogens are those carcinogens that are known with virtual certainty<\/em>\u00a0to cause\u00a0cancer. In addition to UV light,\u00a0Group 1 carcinogens\u00a0include tobacco and plutonium.\u00a0In terms of numbers of cancers caused, UV radiation is far worse than tobacco. More people develop skin cancer because of UV light exposure than develop lung\u00a0cancer\u00a0because of smoking. The increase in cancer risk due to UV light is especially great if you have ever had blistering sunburns as a child or teen.<\/p>\nBesides UV light exposure, other risk factors for skin cancer include:<\/p>\n
\n- Having light coloured skin.<\/li>\n
- Having a lot of moles.<\/li>\n
- Being diagnosed with precancerous skin lesions.<\/li>\n
- Having a family history of skin cancer.<\/li>\n
- Having a personal history of skin cancer.<\/li>\n
- Having a weakened immune system.<\/li>\n
- Being exposed to other forms of radiation or to certain toxic substances such as arsenic.<\/li>\n<\/ul>\n\n
Feature: My\u00a0Human Body<\/h1>\n<\/div>\n
As with most types of cancer, skin cancer is easiest to treat and most likely to be cured the earlier it is detected. The skin is one of the few organs that you can monitor for cancer yourself, as long as you know what to look for. A brown spot on the skin is likely to be a harmless mole, but it could be a sign of skin cancer. As shown in Figure 10.7.5 below, unlike moles, skin cancers may be asymmetrical, have irregular borders, may be very dark in colour, and may have a relatively great diameter. These characteristics can be remembered with the acronym ABCD.<\/p>\n
\nFigure 10.7.5 ABCDs of skin cancer<\/figcaption><\/figure>\n<\/div>\nWith the help of\u00a0mirrors, you should check all of your skin regularly. Look for new skin growths or changes in any existing moles, freckles, bumps, or birthmarks. Report anything suspicious or different to your doctor.<\/p>\n
If you have risk factors for skin cancer, it\u2019s a good idea to have an annual skin check by a dermatologist. This helps ensure that cancerous or precancerous lesions will be detected before they grow too large and become difficult to cure, or in the case of melanoma, before they metastasize.<\/p>\n
\n\n10.7 Summary<\/span><\/h1>\n<\/header>\n\n\n- Skin cancer<\/a> is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to UV light<\/a>, which damages DNA<\/a>. Skin cancer affects more Canadians than all other cancers combined. There are three common types of skin cancer: basal cell carcinoma<\/a>, squamous cell carcinoma<\/a>, and melanoma<\/a>. Carcinomas are more common and unlikely to metastasize. Melanoma is rare and likely to metastasize. It causes most skin cancer deaths.<\/li>\n
- Besides exposure to UV light, risk factors for skin cancer include having light coloured skin, having lots of moles, and a family history of skin cancer, among several others.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n10.7 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- What is skin cancer?<\/li>\n
- How common is skin cancer?<\/li>\n
- \n\n
Figure 10.7.2 Basal cell carcinoma[\/caption]\r\n\r\n[pb_glossary id=\"3927\"]Basal cell carcinoma[\/pb_glossary]<\/strong> occurs in basal cells of the epidermis. Basal cells are [pb_glossary id=\"3163\"]stem cells<\/span>[\/pb_glossary]<\/span> in the [pb_glossary id=\"3542\"]stratum basale[\/pb_glossary] layer that divide to form all the keratinocytes of the epidermis. Basal cell carcinoma is the most common form of skin cancer and 1 in 8 Canadians will develop basal cell carcinoma during their lifetime.\u00a0 A basal cell carcinoma may appear as a pearly or waxy sore, like the one shown in Figure 10.7.2. Basal cell carcinomas rarely spread (or undergo <\/span>[pb_glossary id=\"3928\"]metastasis[\/pb_glossary]<\/strong>)<\/span>,<\/strong>\u00a0so they can generally be cured with a\u00a0<\/span>[pb_glossary id=\"3929\"]biopsy[\/pb_glossary],<\/strong>\u00a0in which the lesion is cut out of the skin and analyzed in a medical lab.<\/span>\r\n Figure 10.7.3 Squamous cell carcinoma[\/caption]\r\n\r\n[pb_glossary id=\"3931\"]Squamous cell carcinoma[\/pb_glossary]<\/strong> occurs in squamous cells of the epidermis. Squamous cells are flattened, [pb_glossary id=\"3525\"]keratin[\/pb_glossary]-filled cells in upper layers of the epidermis. Squamous cell carcinoma is the second most common form of skin cancer. More than two million cases occur in the United States each year. A squamous cell carcinoma may appear as a firm, red nodule, or as a flat lesion with a scaly or crusty surface, like the one pictured in Figure 10.7.3. Squamous cell carcinomas are generally localized and unlikely to metastasize, so they are usually curable surgically.\r\n\r\n \r\n Figure 10.7.4 Melanoma[\/caption]\r\n\r\n[pb_glossary id=\"3933\"]Melanoma[\/pb_glossary]<\/strong> occurs in [pb_glossary id=\"3526\"]melanocytes[\/pb_glossary] of the epidermis. Melanocytes are the melanin-producing cells in the stratum basale of the epidermis. Melanoma is the rarest type of skin cancer, accounting for less than one per cent of all skin cancer cases. Melanoma, however, is the most deadly type of skin cancer. It causes the vast majority of skin cancer deaths, because melanoma is malignant. If not treated, it will metastasize and spread to other parts of the body. If melanoma is detected early and while it is still localized in the skin, most patients survive for at least five years. If melanoma is discovered only after it has already metastasized to distant organs, there is only a 17% of patients surviving for five years. You can see an example of a melanoma in Figure 10.7.4.\r\n\r\nMelanoma can develop anywhere on the body. It may develop in otherwise normal skin, or an existing mole may become cancerous. Signs of melanoma may include a:\r\n- \r\n \t
- Mole that changes in size, feel, or colour.<\/li>\r\n \t
- Mole that bleeds.<\/li>\r\n \t
- Large brown spot on the skin sprinkled with darker specks.<\/li>\r\n \t
- Small lesion with an irregular border and parts that appear red, white, blue, or blue-black.<\/li>\r\n \t
- Dark lesion on the palms, soles, fingertips, toes, or mucous membranes.<\/li>\r\n<\/ul>\r\n\r\n
Skin Cancer Risk Factors<\/h1>\r\n<\/div>\r\nExposure to UV radiation causes about 90 per cent of all skin cancer cases. The connection between skin cancer and UV light is so strong that the World Health Organization has classified UV radiation (whether from tanning beds or the sun) as a Group 1 carcinogen (cancer-causing agent). Group 1 carcinogens are those carcinogens that are known with virtual certainty<\/em>\u00a0to cause\u00a0cancer. In addition to UV light,\u00a0Group 1 carcinogens\u00a0include tobacco and plutonium.\u00a0In terms of numbers of cancers caused, UV radiation is far worse than tobacco. More people develop skin cancer because of UV light exposure than develop lung\u00a0cancer\u00a0because of smoking. The increase in cancer risk due to UV light is especially great if you have ever had blistering sunburns as a child or teen.\r\n\r\nBesides UV light exposure, other risk factors for skin cancer include:\r\n
- \r\n \t
- Having light coloured skin.<\/li>\r\n \t
- Having a lot of moles.<\/li>\r\n \t
- Being diagnosed with precancerous skin lesions.<\/li>\r\n \t
- Having a family history of skin cancer.<\/li>\r\n \t
- Having a personal history of skin cancer.<\/li>\r\n \t
- Having a weakened immune system.<\/li>\r\n \t
- Being exposed to other forms of radiation or to certain toxic substances such as arsenic.<\/li>\r\n<\/ul>\r\n\r\n
Feature: My\u00a0Human Body<\/h1>\r\n<\/div>\r\nAs with most types of cancer, skin cancer is easiest to treat and most likely to be cured the earlier it is detected. The skin is one of the few organs that you can monitor for cancer yourself, as long as you know what to look for. A brown spot on the skin is likely to be a harmless mole, but it could be a sign of skin cancer. As shown in Figure 10.7.5 below, unlike moles, skin cancers may be asymmetrical, have irregular borders, may be very dark in colour, and may have a relatively great diameter. These characteristics can be remembered with the acronym ABCD.\r\n
\r\n\r\n[caption id=\"attachment_3935\" align=\"aligncenter\" width=\"500\"] Figure 10.7.5 ABCDs of skin cancer[\/caption]\r\n\r\n<\/div>\r\nWith the help of\u00a0mirrors, you should check all of your skin regularly. Look for new skin growths or changes in any existing moles, freckles, bumps, or birthmarks. Report anything suspicious or different to your doctor.\r\n\r\nIf you have risk factors for skin cancer, it\u2019s a good idea to have an annual skin check by a dermatologist. This helps ensure that cancerous or precancerous lesions will be detected before they grow too large and become difficult to cure, or in the case of melanoma, before they metastasize.\r\n\r\n 10.7 Summary<\/span><\/h1>\r\n<\/header>\r\n
\r\n- \r\n \t
- Skin [pb_glossary id=\"5605\"]cancer[\/pb_glossary] is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to [pb_glossary id=\"3537\"]UV light[\/pb_glossary], which damages [pb_glossary id=\"277\"]DNA[\/pb_glossary]. Skin cancer affects more Canadians than all other cancers combined. There are three common types of skin cancer: [pb_glossary id=\"3927\"]basal cell carcinoma[\/pb_glossary], [pb_glossary id=\"3931\"]squamous cell carcinoma[\/pb_glossary], and [pb_glossary id=\"3933\"]melanoma[\/pb_glossary]. Carcinomas are more common and unlikely to metastasize. Melanoma is rare and likely to metastasize. It causes most skin cancer deaths.<\/li>\r\n \t
- Besides exposure to UV light, risk factors for skin cancer include having light coloured skin, having lots of moles, and a family history of skin cancer, among several others.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n 10.7 Review Questions<\/span><\/h1>\r\n<\/header>\r\n
\r\n- \r\n \t
- What is skin cancer?<\/li>\r\n \t
- How common is skin cancer?<\/li>\r\n \t
- [h5p id=\"589\"]<\/li>\r\n \t
- Compare and contrast the three common types of skin cancer.<\/li>\r\n \t
- Identify factors that increase the risk of skin cancer.<\/li>\r\n \t
- How does exposure to UV light cause skin cancer?<\/li>\r\n \t
- In which layer of the skin does skin cancer normally start?<\/li>\r\n \t
- Which two skin cancers described in this section start in the same sub-layer? Include the name of the sub-layer and the cells affected in each of these cancers.<\/li>\r\n \t
- Which type of skin cancer is most likely to spread to other organs? Explain your answer.<\/li>\r\n \t
- Which form of skin cancer is the most deadly?<\/li>\r\n \t
- What are some ways people can reduce their risk of getting skin cancer? Explain your answer.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n 10.7 Explore More<\/span><\/h1>\r\n<\/header>\r\n
\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=60e-t4zglBk&feature=emb_logo\r\nThe skin 'beauty' and the sun 'beast': Charareh Pourzand at TEDxBathUniveristy, TEDx Talks, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=ID-O-Ion3EQ&feature=emb_logo\r\n
Cancer of the Vulva, Robert Miller, 2014.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w\r\n
How do cancer cells behave differently from healthy ones? - George Zaidan, TED-Ed, 2012.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n
Attributions<\/h2>\r\nFigure 10.7.1<\/strong>\r\n\r\nStolen_Moment_in_the_Sun<\/a> by Angie Garrett<\/a> on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 10.7.2<\/strong>\r\n\r\nBasal_cell_carcinoma,_ulcerated<\/a> by Kelly Nelson (Photographer) from National Cancer Institute<\/a> (part of the National Institutes of Health)<\/a> with the ID\u00a09237<\/a> on Wikimedia Commons was released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/b>\r\n\r\nFigure 10.7.3<\/strong>\r\n\r\nSquamous_cell_carcinoma_(1)<\/a> by Kelly Nelson (Photographer) from National Cancer Institute<\/a> (part of the National Institutes of Health)<\/a> with the ID\u00a09248<\/a> on Wikimedia Commons was released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/b>\r\n\r\nFigure 10.7.4<\/strong>\r\n\r\nMelanoma<\/a> by Unknown author\u00a0(Photographer) from National Cancer Institute<\/a> (part of the National Institutes of Health)<\/a> with the AV-8500-3850\/ ID 9186<\/a> on Wikimedia Commons was released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/b>\r\n\r\n\r\nFigure 10.7.5<\/strong>\r\n\r\nABCDs of skin cancer<\/a> by CK-12 Foundation<\/a> is used under a CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license. (Original images courtesy of NCI: ID numbers 2362;<\/a> 2363<\/a>; 2364;<\/a> and 2184<\/a>)\r\n
\u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\r\nReferences<\/h2>\r\n
Brainard, J\/ CK-12 Foundation. (2016). Figure 5 ABCDs of skin cancer[digital image]. In CK-12 College Human Biology<\/em> (Section 12.7) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/12.7\/<\/p>\r\n
Public Health Agency of Canada. (2019, December 9). Non melanoma skin cancer. Canada.ca. https:\/\/www.canada.ca\/en\/public-health\/services\/chronic-diseases\/cancer\/non-melanoma-skin-cancer.html<\/a><\/p>\r\n
Robert Miller. (2014, July 22). Cancer of the vulva. YouTube. https:\/\/www.youtube.com\/watch?v=ID-O-Ion3EQ<\/p>\r\n
TED-Ed. (2012, December 5). How do cancer cells behave differently from healthy ones? - George Zaidan. YouTube. https:\/\/www.youtube.com\/watch?v=BmFEoCFDi-w<\/p>\r\n
TEDx Talks. (2014, March 28). The skin 'beauty' and the sun 'beast': Charareh Pourzand at TEDxBathUniveristy. YouTube. https:\/\/www.youtube.com\/watch?v=60e-t4zglBk<\/p>","rendered":"
<\/p>\n
Figure 10.7.1 I hope they’re wearing sunscreen!<\/em><\/figcaption><\/figure>\n \nBathing in Sunshine<\/h1>\n<\/div>\n
Summer sun may feel good on your body, but its invisible UV rays<\/a> wreak havoc on your skin. Exposing the skin to UV light causes photo-aging: premature wrinkling, brown discolourations, and other unattractive signs of sun exposure. Even worse, UV light increases your risk of skin cancer.<\/p>\n
\nWhat Is Skin Cancer?<\/h1>\n<\/div>\n
Skin cancer<\/a> is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to UV light, which damages DNA<\/a>. Therefore, skin cancer most often develops on areas of the skin that are frequently exposed to UV light. However, it can also occur on areas that are rarely exposed to UV light. Skin cancer affects people of all skin colours, including those with dark skin. It also affects more people altogether than all other cancers combined. One in five Canadians develops skin cancer in his or her lifetime.<\/p>\n
\nTypes of Skin Cancer<\/h1>\n<\/div>\n
Skin cancer begins in the outer layer of skin, the\u00a0epidermis<\/a>. There are three common types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma.<\/p>\n
Basal Cell Carcinoma<\/h2>\n
Figure 10.7.2 Basal cell carcinoma<\/figcaption><\/figure>\n Basal cell carcinoma<\/a><\/strong> occurs in basal cells of the epidermis. Basal cells are stem cells<\/span><\/a><\/span> in the stratum basale<\/a> layer that divide to form all the keratinocytes of the epidermis. Basal cell carcinoma is the most common form of skin cancer and 1 in 8 Canadians will develop basal cell carcinoma during their lifetime.\u00a0 A basal cell carcinoma may appear as a pearly or waxy sore, like the one shown in Figure 10.7.2. Basal cell carcinomas rarely spread (or undergo <\/span>metastasis<\/a><\/strong>)<\/span>,<\/strong>\u00a0so they can generally be cured with a\u00a0<\/span>biopsy<\/a>,<\/strong>\u00a0in which the lesion is cut out of the skin and analyzed in a medical lab.<\/span><\/p>\n
\nSquamous Cell Carcinoma<\/span><\/p>\n<\/div>\n
Figure 10.7.3 Squamous cell carcinoma<\/figcaption><\/figure>\n Squamous cell carcinoma<\/a><\/strong> occurs in squamous cells of the epidermis. Squamous cells are flattened, keratin<\/a>-filled cells in upper layers of the epidermis. Squamous cell carcinoma is the second most common form of skin cancer. More than two million cases occur in the United States each year. A squamous cell carcinoma may appear as a firm, red nodule, or as a flat lesion with a scaly or crusty surface, like the one pictured in Figure 10.7.3. Squamous cell carcinomas are generally localized and unlikely to metastasize, so they are usually curable surgically.<\/p>\n
<\/p>\n
\nMelanoma<\/span><\/p>\n<\/div>\n
Figure 10.7.4 Melanoma<\/figcaption><\/figure>\n Melanoma<\/a><\/strong> occurs in melanocytes<\/a> of the epidermis. Melanocytes are the melanin-producing cells in the stratum basale of the epidermis. Melanoma is the rarest type of skin cancer, accounting for less than one per cent of all skin cancer cases. Melanoma, however, is the most deadly type of skin cancer. It causes the vast majority of skin cancer deaths, because melanoma is malignant. If not treated, it will metastasize and spread to other parts of the body. If melanoma is detected early and while it is still localized in the skin, most patients survive for at least five years. If melanoma is discovered only after it has already metastasized to distant organs, there is only a 17% of patients surviving for five years. You can see an example of a melanoma in Figure 10.7.4.<\/p>\n
Melanoma can develop anywhere on the body. It may develop in otherwise normal skin, or an existing mole may become cancerous. Signs of melanoma may include a:<\/p>\n
- \n
- Mole that changes in size, feel, or colour.<\/li>\n
- Mole that bleeds.<\/li>\n
- Large brown spot on the skin sprinkled with darker specks.<\/li>\n
- Small lesion with an irregular border and parts that appear red, white, blue, or blue-black.<\/li>\n
- Dark lesion on the palms, soles, fingertips, toes, or mucous membranes.<\/li>\n<\/ul>\n\n
Skin Cancer Risk Factors<\/h1>\n<\/div>\n
Exposure to UV radiation causes about 90 per cent of all skin cancer cases. The connection between skin cancer and UV light is so strong that the World Health Organization has classified UV radiation (whether from tanning beds or the sun) as a Group 1 carcinogen (cancer-causing agent). Group 1 carcinogens are those carcinogens that are known with virtual certainty<\/em>\u00a0to cause\u00a0cancer. In addition to UV light,\u00a0Group 1 carcinogens\u00a0include tobacco and plutonium.\u00a0In terms of numbers of cancers caused, UV radiation is far worse than tobacco. More people develop skin cancer because of UV light exposure than develop lung\u00a0cancer\u00a0because of smoking. The increase in cancer risk due to UV light is especially great if you have ever had blistering sunburns as a child or teen.<\/p>\n
Besides UV light exposure, other risk factors for skin cancer include:<\/p>\n
- \n
- Having light coloured skin.<\/li>\n
- Having a lot of moles.<\/li>\n
- Being diagnosed with precancerous skin lesions.<\/li>\n
- Having a family history of skin cancer.<\/li>\n
- Having a personal history of skin cancer.<\/li>\n
- Having a weakened immune system.<\/li>\n
- Being exposed to other forms of radiation or to certain toxic substances such as arsenic.<\/li>\n<\/ul>\n\n
Feature: My\u00a0Human Body<\/h1>\n<\/div>\n
As with most types of cancer, skin cancer is easiest to treat and most likely to be cured the earlier it is detected. The skin is one of the few organs that you can monitor for cancer yourself, as long as you know what to look for. A brown spot on the skin is likely to be a harmless mole, but it could be a sign of skin cancer. As shown in Figure 10.7.5 below, unlike moles, skin cancers may be asymmetrical, have irregular borders, may be very dark in colour, and may have a relatively great diameter. These characteristics can be remembered with the acronym ABCD.<\/p>\n
\nFigure 10.7.5 ABCDs of skin cancer<\/figcaption><\/figure>\n<\/div>\n With the help of\u00a0mirrors, you should check all of your skin regularly. Look for new skin growths or changes in any existing moles, freckles, bumps, or birthmarks. Report anything suspicious or different to your doctor.<\/p>\n
If you have risk factors for skin cancer, it\u2019s a good idea to have an annual skin check by a dermatologist. This helps ensure that cancerous or precancerous lesions will be detected before they grow too large and become difficult to cure, or in the case of melanoma, before they metastasize.<\/p>\n
\n\n 10.7 Summary<\/span><\/h1>\n<\/header>\n
\n- \n
- Skin cancer<\/a> is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to UV light<\/a>, which damages DNA<\/a>. Skin cancer affects more Canadians than all other cancers combined. There are three common types of skin cancer: basal cell carcinoma<\/a>, squamous cell carcinoma<\/a>, and melanoma<\/a>. Carcinomas are more common and unlikely to metastasize. Melanoma is rare and likely to metastasize. It causes most skin cancer deaths.<\/li>\n
- Besides exposure to UV light, risk factors for skin cancer include having light coloured skin, having lots of moles, and a family history of skin cancer, among several others.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\n\n 10.7 Review Questions<\/span><\/h1>\n<\/header>\n
\n- \n
- What is skin cancer?<\/li>\n
- How common is skin cancer?<\/li>\n
- \n\n
- Besides exposure to UV light, risk factors for skin cancer include having light coloured skin, having lots of moles, and a family history of skin cancer, among several others.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
- Skin cancer<\/a> is a disease in which skin cells grow out of control. It is caused mainly by excessive exposure to UV light<\/a>, which damages DNA<\/a>. Skin cancer affects more Canadians than all other cancers combined. There are three common types of skin cancer: basal cell carcinoma<\/a>, squamous cell carcinoma<\/a>, and melanoma<\/a>. Carcinomas are more common and unlikely to metastasize. Melanoma is rare and likely to metastasize. It causes most skin cancer deaths.<\/li>\n
![Stolen_Moment_in_the_Sun<\/a> by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Stolen_Moment_in_the_Sun.jpg\"){kind=link}
![Basal_cell_carcinoma,_ulcerated<\/a> by Kelly Nelson (Photographer) from](\"https:\/\/commons.wikimedia.org\/wiki\/File:Basal_cell_carcinoma,_ulcerated.jpg\"){kind=link}
![Squamous_cell_carcinoma_(1)<\/a> by Kelly Nelson (Photographer) from](\"https:\/\/commons.wikimedia.org\/wiki\/File:Squamous_cell_carcinoma_(1).jpg\"){kind=link}
![Melanoma<\/a> by Unknown author\u00a0(Photographer) from](\"https:\/\/commons.wikimedia.org\/wiki\/File:Melanoma.jpg\"){kind=link}