Editing Skin cancer (section)

== Classification ==

There are three main types of skin cancer: [[basal-cell skin cancer]] (basal-cell carcinoma) (BCC), [[squamous-cell skin cancer]] (squamous-cell carcinoma) (SCC) and [[malignant melanoma]].
{| class="wikitable" style="margin:1em auto;"
! Cancer
! Description
! Illustration
|-
| [[Basal-cell carcinoma]]
| Note the pearly translucency to fleshy color, tiny blood vessels on the surface, and sometimes ulceration which can be characteristics. The key term is translucency.
| [[File:Basal cell carcinoma3.JPG|center|150px]]
|-
| [[Squamous-cell skin carcinoma]]
| Commonly presents as a red, crusted, or scaly patch or bump. Often a very rapidly growing tumor.
| [[File:Squamous Cell Carcinoma1.jpg|center|150px]]
|-
| [[Melanoma|Malignant melanoma]]
| These are commonly asymmetrical in shape and/or pigment distribution, with an irregular border, color variation, and often greater than 6&nbsp;mm diameter.<ref>{{cite web | vauthors =  Swetter SM | date = 30 August 2010 |url= http://emedicine.medscape.com/article/1100753-overview |title=Malignant Melanoma | work = eMedicine Dermatology|url-status=live|archive-url=https://web.archive.org/web/20101007220016/http://emedicine.medscape.com/article/1100753-overview|archive-date=7 October 2010 }}</ref>
|  [[File:Melanoma.jpg|center|150px]]
|}

Basal-cell carcinomas are most commonly present on sun-exposed areas of the skin, especially the face. They rarely metastasize and rarely cause death. They are easily treated with surgery or radiation. Squamous-cell skin cancers are also common, but much less common than basal-cell cancers. They metastasize more frequently than BCCs. Even then, the metastasis rate is quite low, with the exception of SCC of the lip or ear, and in people who are immunosuppressed. Melanoma are the least frequent of the three common skin cancers. They frequently metastasize, and can cause death once they spread.

Less common skin cancers include:  [[Merkel cell carcinoma]], [[Paget's disease of the breast]], atypical fibroxanthoma, [[porocarcinoma]], spindle cell tumors, [[sebaceous carcinoma]]s, [[microcystic adnexal carcinoma]], [[keratoacanthoma]], and  [[skin sarcoma]]s, such as [[angiosarcoma]], [[dermatofibrosarcoma protuberans]], [[Kaposi's sarcoma]],  [[leiomyosarcoma]].

BCC and SCC often carry a UV-signature mutation indicating that these cancers are caused by [[UVB]] radiation via direct DNA damage. However, malignant melanoma is predominantly caused by UVA radiation via indirect DNA damage. The indirect DNA damage is caused by free radicals and reactive oxygen species. Research indicates that the absorption of three sunscreen ingredients into the skin, combined with a 60-minute exposure to UV, leads to an increase of [[free radicals]] in the skin, if applied in too little quantity and too infrequently.<ref name="Hanson">{{cite journal | vauthors = Hanson KM, Gratton E, Bardeen CJ | title = Sunscreen enhancement of UV-induced reactive oxygen species in the skin | journal = Free Radical Biology & Medicine | volume = 41 | issue = 8 | pages = 1205–1212 | date = October 2006 | pmid = 17015167 | doi = 10.1016/j.freeradbiomed.2006.06.011 | s2cid = 13999532 | url = https://escholarship.org/content/qt9f14s2dd/qt9f14s2dd.pdf?t=oe9hj9 }}</ref> However, the researchers add that newer creams often do not contain these specific compounds, and that the combination of other ingredients tends to retain the compounds on the surface of the skin. They also add that frequent re-application reduces the risk of radical formation.