Squamous cell carcinoma is a common form of skin cancer; only basal cell carcinoma occurs more frequently. It is most common in older adults, but it is becoming more common in people under 40 years old. It is strongly associated with unprotected exposure to UV radiation, such as that produced by the sun and by tanning lamps and beds.


Squamous cell carcinoma develops from cells deep within the epidermis called, unsurprisingly, squamous cells. The DNA within these cells can be damaged by exposure to UV radiation, causing them to reproduce abnormally. Instead of the normal pattern of cell death and new cell formation, the damaged squamous cells grow out of control.


Lesions caused by squamous cell carcinoma almost always occur on sun-exposed skin, but occasionally appear on other parts of the body such as the mouth, genitals and anus. The tumors usually grow slowly and may go unnoticed for months or years. They can take on many different appearances, which make them impossible to definitively diagnose without a biopsy. The lesions are usually painless but may itch.


Squamous cell carcinoma may be suspected based on the appearance of a lesion on the skin, but the diagnosis must be confirmed with a biopsy. "Shave" biopsies are usually performed to test for this condition. To perform a shave biopsy, a doctor uses a scalpel to cut away a very thin layer of the growth. The tissue sample is then sent to a pathologist for microscopic examination.


Almost all cases of squamous cell carcinoma are caused by exposure to sunlight or tanning lights. However, the risk of developing the disease is higher in some people than others, even if they have been exposed to the same amount of UV radiation. Those who are most at risk are men, fair-skinned people (especially those who are of Northern European descent), people who have an impaired immune system and smokers. Certain disorders can also increase your risk of developing squamous cell carcinoma; these include inflammatory skin conditions, such as psoriasis, and xeroderma pigmentosum, a rare genetic disorder that causes severe sensitivity to sunlight.


The most important measure you can take to prevent squamous cell carcinoma is to avoid excessive exposure to UV radiation by wearing sunscreen and avoiding tanning lights. Treatment for squamous cell carcinoma usually consists of removing the lesion, either by freezing, excision or laser therapy. In some cases, radiation or creams containing chemotherapy agents are used to treat squamous cell carcinoma in areas where scarring is of concern. Although rare, squamous cell carcinoma can sometimes spread and require additional treatment.