Merck Manual

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Overview of Skin Cancer


Gregory L. Wells

, MD, Ada West Dermatology and Dermatopathology

Reviewed/Revised Sep 2022
Topic Resources

Skin cancer is the most common type of cancer and commonly develops in sun-exposed areas of skin. The incidence is highest among outdoor workers, sportsmen, and sunbathers and is inversely related to the amount of melanin skin pigmentation; fair-skinned people are most susceptible. Skin cancers may also develop years after therapeutic x-rays or exposure to carcinogens (eg, arsenic ingestion).

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

The most common forms of skin cancer are

The less common forms of skin cancer are

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.

Pearls & Pitfalls

  • Biopsy any skin lesion, whether appearance is typical for cancer or atypical, that enlarges or persists longer than expected.


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. (See also the US Preventive Services Task Force summary of recommendations for screening for skin cancer and counseling for skin cancer.)


Because many skin cancers seem to be related to 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

More Information

The following English-language resources may be useful. Please note that THE MANUAL is not responsible for the content of these resources.

NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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