Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Basal Cell Carcinoma

What Is It?

Basal cells are small, round skin cells normally found in the upper part of your skin (called the epidermis). When these cells become cancerous, they grow out of control, and typically turn into small skin tumors that sometimes destroy skin and nearby tissues. This can be especially devastating if a basal cell cancer develops on the face, where it can cause disfigurement, and can interfere with the function of the eyelids, nose, and mouth. Basal cell tumors rarely spread (metastasize) or cause death, but they can grow large over time, causing damage around and under them.

Like the two other common forms of skin cancer — squamous cell carcinoma and malignant melanoma — basal cell cancer often develop because of repeated, long-term exposure to the sun. That's why basal cell cancer is most common in people who spend a great deal of time in the sun, especially if they have light skin and blue eyes. Less often, basal cell cancer may be caused by exposure to arsenic or certain industrial pollutants. Older people who received X-ray treatment for acne as teenagers are at higher risk of developing basal cell cancer.

Basal cell cancer is the most common form of skin cancer diagnosed in the United States. More than 750,000 people are treated for it every year. Although about 90 percent of basal cell cancers are found on some part of the face, this cancer can grow on any part of the body, especially on unprotected portions of the body exposed to sunlight.