Overview of Skin Cancer

Skin cancer is the most common type of cancer and commonly develops in sun-exposed areas of skin. Skin cancers can be found on any location of the body but are most commonly diagnosed on the head and neck (ie, areas of chronic sun exposure).

The incidence is highest among people who spend a lot of time outdoors for work or recreation and is inversely related to the amount of melanin skin pigmentation; people who have light skin are most susceptible.

Skin cancers may also develop years after therapeutic radiation or exposure to carcinogens (eg, arsenic ingestion).

Over 5.4 million new cases of nonmelanoma skin cancer were diagnosed in 2012 in over 3.3 million people in the United States. (See The Skin Cancer Foundation.)

The most common forms of skin cancer are

• Basal cell carcinoma (approximately 80%) (1)

• Squamous cell carcinoma

• Melanoma

In a 2019 nationwide study in the United States, incidences per 100,000 people were: basal cell carcinoma, 525; squamous cell carcinoma, 262; and melanoma, 17.0 (2).

The less common forms of skin cancer are

• Paget disease of the breast or extramammary Paget disease (usually in the groin or near the anus)

• Kaposi sarcoma

• Merkel cell carcinoma

• Atypical fibroxanthomas

• Tumors of the adnexa

• Cutaneous T-cell lymphoma (mycosis fungoides)

Squamous cell carcinoma in situ (formerly called Bowen disease) is a superficial squamous cell carcinoma. Keratoacanthoma may be a well-differentiated form of squamous cell carcinoma.

Initially, skin cancers are often asymptomatic. The most frequent presentation is an irregular red or pigmented lesion that does not go away. Any lesion that appears to be enlarging should be biopsied—whether tenderness, mild inflammation, crusting, or occasional bleeding is present or not. If treated early, most skin cancers are curable.

Prevention of Skin Cancer

Sun Protection Myths

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Because many skin cancers are likely associated with ultraviolet (UV) exposure, a number of measures are recommended to limit exposure.

• Sun avoidance: Seeking shade, minimizing outdoor activities between 10 AM and 4 PM (when sun's rays are strongest), and avoiding sunbathing and the use of tanning beds

• Use of protective clothing: Long-sleeved shirts, pants, and broad-brimmed hats

• Use of sunscreen: At least sun protection factor (SPF) 30 with broad-spectrum UVA/UVB protection, used as directed (ie, reapplied every 2 hours and after swimming or sweating); should not be used to prolong sun exposure

Current evidence is inadequate to determine whether these measures reduce incidence or mortality of melanoma; in nonmelanoma skin cancers (basal cell carcinoma and squamous cell carcinoma), sun protection does decrease the incidence of new cancers (1).

Screening

Some professional organizations support clinical examination and self-examination to screen for skin cancer; however, the US Preventive Services Task Force has not found sufficient evidence to do so for the general population. (See also the US Preventive Services Task Force summary of recommendations for screening for skin cancer and counseling about skin cancer.)

High-risk patients, such as those taking immunosuppressants, those with a personal or strong family history of skin cancer, or those with a known, increased susceptibility to skin cancer because of specific genetic mutations or environmental exposures, should be considered for routine skin cancer surveillance.

Prevention reference

1. 1. Green A, Williams G, Neale R, et al: Daily sunscreen application and betacarotene supplementation in prevention of basal-cell and squamous-cell carcinomas of the skin: a randomised controlled trial. Lancet 354(9180):723-729, 1999. doi: 10.1016/S0140-6736(98)12168-2