Squamous cell carcinoma, the second most common skin cancer after basal cell carcinoma, afflicts more than 1,000,000 Americans each year. It arises from the epidermis and affects the squamous cells that comprise most of the upper layers of skin. Squamous cell cancers may occur on all areas of the body including the mucous membranes, but are most common in areas exposed to the sun.
Although squamous cell carcinomas usually remain confined to the epidermis for some time, they eventually penetrate the underlying tissues if not treated. In a small percentage of cases, they spread (metastasize) to distant tissues and organs. When this happens, they can he fatal. Squamous cell carcinomas that metastasize most often arise on sites of chronic inflammatory skin conditions or on the mucous membranes or lips, or occur in immunocompromised individuals, i.e., people who have leukemia or lymphoma, or who are organ transplant recipients.
What causes it?
Chronic exposure to sunlight causes most cases of squamous cell carcinoma. That is why tumors appear most frequently on sun-exposed parts of the body: the face, neck, bald scalp, hands, shoulders, arms, and back. The rim of the ears and the lower lip are especially vulnerable to the development of these cancers.
Squamous cell carcinomas may also occur where skin has suffered certain kinds of injury such as burns, scars, long-standing sores, or sites previously exposed to X-rays or certain chemicals (such as arsenic and petroleum by-products). In addition, chronic skin inflammation or medical conditions that suppress the immune system over an extended period of time may encourage development of squamous cell carcinoma.
Occasionally, squamous cell carcinoma arises spontaneously on what appears to be normal, healthy, undamaged skin. Some researchers believe that a tendency to develop this cancer may be inherited.
Who gets it?
Anyone with a substantial history of sun exposure can develop squamous cell carcinoma. But people who have fair skin, light hair, and blue, green, or gray eyes are at highest risk. Those whose occupations require long hours outdoors or who spend extensive leisure time in the sun are in particular jeopardy.
Dark-skinned individuals of African descent are far less likely than fair-skinned individuals to develop skin cancer. More than two-thirds of the skin cancers that they do develop, however, are squamous cell carcinomas, usually arising on the sites of preexisting inflammatory skin conditions or burn injuries.
How can I protect myself and my family?
When detected early, squamous cell carcinomas are treatable and curable in the majority of cases. But the first and best line of defense against squamous cell carcinoma and other skin cancers is prevention. Be sure to make these sun safety habits part of your health care routine from now on:
- Do not sunbathe
- Avoid unnecessary sun exposure, especially between 10:00 a.m. and 4:00 p.m., the peak hours for harmful ultraviolet (UVB) radiation
- When outdoors, use sunscreens rated SPF 30 or higher. Apply them liberally, uniformly, and frequently
- When exposed to sunlight, wear protective clothing such as long pants, long-sleeved shirts, broad-brimmed hats, and UV-protective sunglasses
- Stay away from artificial tanning devices
- Teach your children good sun protection habits at an early age, as the damage that leads to adult skin cancers starts in childhood
- Examine your skin head to toe at least once every three months
Jeffrey H. Binstock, MD is a Fellow of:
