Squamous cell carcinoma

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Squamous cell carcinoma is cancer that begins in the squamous cells of the skin.

Thick, scaly growths appear on the skin and do not heal.
To diagnose the cancer, doctors do a biopsy.
Treatment with surgery, chemotherapy drugs applied to the skin, and sometimes radiation therapy can usually cure the cancer unless it has spread.
If the cancer spreads to other parts of the body, it can be fatal.

(See also Overview of Skin Cancer.)
Squamous cells (keratinocytes) are the main structural cells of the epidermis (the outer layer of skin). Squamous cell carcinoma is cancer of these cells. Each year in the United States, more than a million people are diagnosed with squamous cell carcinoma, and 2,500 die from it.
Squamous cell carcinoma, the second most common type of skin cancer after basal cell carcinoma, usually develops on sun-exposed areas but may grow anywhere on the skin or in the mouth, where sun exposure is minimal. However, people who have had more sun exposure to their skin have a higher risk of developing squamous cell skin cancer. Fair-skinned people are much more susceptible to squamous cell carcinoma than darker-skinned people.
Squamous cell carcinoma may develop on normal skin but is more likely to develop in damaged skin. Such damage includes

Precancerous skin growths caused by previous sun exposure (actinic keratoses)
Chronic sores on the skin or in the mucus membranes (such as those that line the eyes, nose, and lungs) or genitals
Skin that has been scarred, particularly by burns

In the mouth, precancerous skin growths appear as white or red spots (leukoplakia or erythroplakia).
Bowen disease and possibly keratoacanthomas are forms of squamous cell carcinoma.