A Quarter of a Million Americans
More than 700,000 new cases of squamous cell carcinoma (SCC) are diagnosed every year. That makes it the second most common skin cancer (after basal cell carcinoma).
This form of skin cancer arises in the squamous cells that make up most of the skins upper layers (epidermis). Squamous cell carcinomas may occur on all areas of the body including the mucous membranes and genitals, but are most common in areas frequently exposed to the sun, such as the rim of the ear, lower lip, face, bald scalp, neck, hands, arms and legs. Often the skin in these areas reveals telltale signs of sun damage, such as wrinkling, changes in pigmentation, and loss of elasticity.
Who Gets It
People who have fair skin, light hair, and blue, green, or gray eyes are at highest risk of developing the disease. But anyone with a history of substantial sun exposure is at increased risk. Those whose occupations require long hours outdoors or who spend extensive leisure time in the sun are in particular jeopardy. Anyone who has had a basal cell carcinoma is also more likely to develop an squamous cell carcinoma, as is anyone with an inherited, highly UV-sensitive condition such as xeroderma pigmentosum.
Squamous cell carcinomas are at least twice as frequent in men as in women. They rarely appear before age 50 and are most often seen in individuals in their 70s.
The majority of skin cancers in African-Americans are squamous cell carcinomas, usually arising on the sites of preexisting inflammatory skin conditions or burn injuries. Though naturally dark-skinned people are less likely than fair-skinned people to get skin cancer, it is still essential for them to practice sun protection.
Chronic exposure to sunlight causes most cases of squamous cell carcinoma. Frequent use of tanning beds also multiplies the risk of squamous cell carcinoma; people who use tanning beds are 2.5 times more likely to develop squamous cell carcinoma than those who dont. But skin injuries are another important source. The cancer can arise in burns, scars, ulcers, long-standing sores and sites previously exposed to X-rays or certain chemicals (such as arsenic and petroleum by-products).
Chronic infections and skin inflammation can also give rise to squamous cell carcinoma. Furthermore, HIV and other immune deficiency diseases, chemotherapy, anti-rejection drugs used in organ transplantation, and even excessive sun exposure itself all weaken the immune system, making it harder to fight off disease and thus increasing the risk of squamous cell carcinoma and other skin cancers.
Occasionally, squamous cell carcinomas arise spontaneously on what appears to be normal, healthy skin. Some researchers believe the tendency to develop these cancers can be inherited.