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.