It doesn't get as much attention as other skin cancers, but squamous cell cancer is common and serious.
Summer's the season for fun in the sun — but also for skin cancer. Of the three main types of skin cancer, melanoma is most deadly, and basal cell, most common. Squamous cell cancer falls in between. It's three times as common as melanoma (some 200,000 new cases each year versus 62,000). Though not as common as basal cell (about one million new cases a year), squamous cell is more serious because it is likely to spread (metastasize). Treated early, the cure rate is over 90%, but metastases occur in 1%–5% of cases. After it has metastasized, it's very difficult to treat.
What it looks like
Squamous cell cancer involves the runaway growth of keratinocytes, cells in the outermost layer of skin, which produce the protein keratin. Squamous means scaly; in 60%–80% of cases, the lesions emerge on or near scaly patches called actinic keratoses that develop from sun-damaged skin.
Typically, such lesions are hard (from the keratin), well-defined, and occasionally crusty. You might mistake one for a wart, only flatter. Others are soft and fleshy. The pictures on our Web site will help you get a better idea of what it looks like.
Exposure to sunlight is the main risk factor for skin cancer. For melanoma, sporadic instances of intense exposure seem to be triggers. For squamous cell cancer, cumulative exposure and possibly the intensity of the sunlight may be more significant. As with all skin cancers, skin color is relevant; those with darker skin (African Americans, Africans, Asians) have lower rates of squamous cell cancer than Caucasians — and among Caucasians, lighter-skinned people are more vulnerable.
Organ transplant recipients are especially vulnerable to squamous cell cancer. European research suggests that heart and kidney recipients are 65–250 times more likely to get squamous cell cancer than the general population. The most likely explanation is that the drugs that transplant patients take to suppress their immune systems and prevent organ rejection also make them vulnerable to this skin cancer. A history of sun exposure before or after the transplant heightens the risk.
Chronic inflammation is another risk factor. The squamous cancers sometimes emerge from chronically inflamed scars or sores.
Treatments for squamous cell cancer all have the same goal: Get rid of the cancer cells, while avoiding unnecessary harm to surrounding skin.
Cryotherapy (rapid freezing) and radiation are used if the lesion is small and not likely to metastasize. Cryotherapy is fast and inexpensive but can leave a whitish mark. Radiation gives the doctor pinpoint control, minimizing damage to healthy skin, but it's expensive, involves many visits, and could result in a more aggressive case if the cancer recurs. Ointments are useful if there are many lesions but can cause stinging, burning, and oozing.
Surgery is the main therapy for larger lesions, and Mohs surgery is becoming the standard, especially for lesions on the face, where cosmetic results matter. Dr. Frederic Mohs, of the University of Wisconsin, developed the procedure during the 1930s and '40s. It involves shaving thin, horizontal slices from the lesion and microscopically examining each one for cancer cells. This cut-examine-cut-examine technique has two advantages. First, it takes the guesswork out of how deep to cut, so the surgeon is less likely to remove healthy tissue while operating. Second, it's less likely to leave cancer cells behind, which may explain why it tends to have a higher cure rate than other techniques.
Drawbacks include cost and time. It's done on an outpatient basis, and patients may spend hours waiting while the surgeon inspects each slice. Some doctors believe the technique may be overused and should be restricted to high-risk or cosmetically sensitive lesions.
Sun safety is fairly straightforward. Avoid being outdoors between 11 a.m. and 4 p.m., when the sun is most intense. Remember that exposure doesn't just happen at the beach. By some estimates 80% of it is incidental to everyday activities like walking the dog, running errands, and so on. Noses, ears, and necks are especially vulnerable, so wear a wide-brimmed hat. A baseball cap offers no protection to your ears and neck (or, if it's worn backwards, your nose and face).
Sunscreen isn't a magic shield. The National Cancer Institute (NCI) says the evidence that it prevents squamous cell skin cancer is only "fair." (For basal cell cancer and melanoma, the NCI says there is inadequate evidence to know if sunscreen is preventive.) In fact, some argue that by preventing sunburn, sunscreens offer a false sense of security, encouraging people to stay in the sun too long. Sunscreen users should buy one with a sun protection factor (SPF) of at least 15. Be sure to put on enough lotion. You need almost three tablespoonfuls on your face, neck, arms, trunk, and legs per application. At least a teaspoon should go on your face and neck.
As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.