Editing Skin cancer (section)

== Causes ==
Ultraviolet radiation from sun exposure is the primary environmental cause of skin cancer.<ref>{{cite journal | vauthors = Narayanan DL, Saladi RN, Fox JL | title = Ultraviolet radiation and skin cancer | journal = International Journal of Dermatology | volume = 49 | issue = 9 | pages = 978–986 | date = September 2010 | pmid = 20883261 | doi = 10.1111/j.1365-4632.2010.04474.x | s2cid = 22224492 | doi-access = free }}</ref><ref name=Review05>{{cite journal | vauthors = Saladi RN, Persaud AN | title = The causes of skin cancer: a comprehensive review | journal = Drugs of Today | volume = 41 | issue = 1 | pages = 37–53 | date = January 2005 | pmid = 15753968 | doi = 10.1358/dot.2005.41.1.875777 }}</ref><ref>{{cite journal | vauthors = Gordon R | title = Skin cancer: an overview of epidemiology and risk factors | journal = Seminars in Oncology Nursing | volume = 29 | issue = 3 | pages = 160–169 | date = August 2013 | pmid = 23958214 | doi = 10.1016/j.soncn.2013.06.002 }}</ref><ref>{{cite journal | vauthors = Mata DA, Williams EA, Sokol E, Oxnard GR, Fleischmann Z, Tse JY, Decker B | title = Prevalence of UV Mutational Signatures Among Cutaneous Primary Tumors | journal = JAMA Network Open | volume = 5 | issue = 3 | pages = e223833 | date = March 2022 | pmid = 35319765 | pmc = 8943639 | doi = 10.1001/jamanetworkopen.2022.3833 | s2cid = 247616874 }}</ref> This can occur in professions such as farming. Other risk factors that play a role include:
* Light skin color<ref name="Review05" />
* Age<ref name="Review05" />
* Smoking [[tobacco]]<ref name="Review05" />
* [[HPV]] infections increase the risk of squamous-cell skin cancer.<ref name="Review05" />
* Some genetic syndromes<ref name="Review05" /> including [[congenital melanocytic nevi syndrome]] which is characterized by the presence of [[Nevus|nevi]] (birthmarks or moles) of varying size which are either present at birth, or appear within 6 months of birth. Nevi larger than {{convert|20|mm|in|frac=4|abbr=on}} in size are at higher risk for becoming cancerous.
* Chronic non-healing wounds.<ref name="Review05" /> These are called [[Marjolin's ulcer]]s based on their appearance, and can develop into squamous-cell skin cancer.
* [[Ionizing radiation]] such as X-rays, environmental [[carcinogens]], and artificial UV radiation (e.g. [[tanning beds]]).<ref name="Review05" /> It is believed that tanning beds are the cause of hundreds of thousands of basal and squamous-cell skin cancer.<ref>{{cite journal | vauthors = Wehner MR, Shive ML, Chren MM, Han J, Qureshi AA, Linos E | title = Indoor tanning and non-melanoma skin cancer: systematic review and meta-analysis | journal = BMJ | volume = 345 | pages = e5909 | date = October 2012 | pmid = 23033409 | pmc = 3462818 | doi = 10.1136/bmj.e5909 }}</ref> The World Health Organization now places people who use artificial tanning beds in its highest risk category for skin cancer.<ref>{{cite book | vauthors = Arndt KA | date = 2010 | title = Skin Care and Repair | location = Chestnut Hill, MA | publisher = Harvard Health Publications }}</ref>
* Alcohol consumption, specifically excessive drinking increase the risk of sunburns.<ref>{{cite journal | vauthors = Saladi RN, Nektalova T, Fox JL | title = Induction of skin carcinogenicity by alcohol and ultraviolet light | journal = Clinical and Experimental Dermatology | volume = 35 | issue = 1 | pages = 7–11 | date = January 2010 | pmid = 19778305 | doi = 10.1111/j.1365-2230.2009.03465.x | s2cid = 35392237 }}</ref>
* The use of many [[immunosuppressive drug|immunosuppressive]] medications increases the risk of skin cancer.<ref>{{cite journal | vauthors = Roche CD, Dobson JS, Williams SK, Quante M, Popoola J, Chow JW | title = Malignant and noninvasive skin tumours in renal transplant recipients | journal = Dermatology Research and Practice | volume = 2014 | pages = 409058 | date = 2014 | pmid = 25302063 | pmc = 4180396 | doi = 10.1155/2014/409058 | doi-access = free }}</ref> [[Cyclosporin A]], a [[calcineurin inhibitor]] for example increases the risk approximately 200 times, and [[azathioprine]] about 60 times.<ref>{{cite journal | vauthors = Kuschal C, Thoms KM, Schubert S, Schäfer A, Boeckmann L, Schön MP, Emmert S | title = Skin cancer in organ transplant recipients: effects of immunosuppressive medications on DNA repair | journal = Experimental Dermatology | volume = 21 | issue = 1 | pages = 2–6 | date = January 2012 | pmid = 22151386 | doi = 10.1111/j.1600-0625.2011.01413.x | s2cid = 25776283 | doi-access = free }}</ref>
* Deliberate exposure of sensitive skin not normally exposed to sunlight during [[wellness (alternative medicine)|alternative wellness]] behaviors such as [[perineum]] sunning.

===UV-induced DNA damage===

[[ultraviolet|UV-irradiation]] of skin cells causes [[DNA damage (naturally occurring)|damage to DNA]] through [[photochemistry|photochemical reactions]].<ref name="lee">{{cite journal | vauthors = Lee JW, Ratnakumar K, Hung KF, Rokunohe D, Kawasumi M | title = Deciphering UV-induced DNA Damage Responses to Prevent and Treat Skin Cancer | journal = Photochemistry and Photobiology | volume = 96 | issue = 3 | pages = 478–499 | date = May 2020 | pmid = 32119110 | pmc = 7651136 | doi = 10.1111/php.13245 }}</ref> Cyclobutane [[pyrimidine dimer]]s formed by adjacent thymine bases, or by adjacent cytosine bases, are frequent types of DNA damage induced by UV.<ref name=lee/> Human skin cells are capable of repairing most UV-induced damage by [[nucleotide excision repair]], a process that protects against skin cancer, but may be inadequate at high levels of exposure.<ref name=lee/>