Basal cell carcinoma is a cancer that originates in cells of the outer layer of skin (epidermis).

• Usually, a small, shiny bump appears on the skin and enlarges slowly.
• The bumps may break open and form a scab, sometimes with bleeding, or become flat, resembling a scar.
• Although this cancer can often be identified by sight, doctors usually do a biopsy.
• The cancer is removed, and chemotherapy drugs may also be applied to the skin.

Basal cells are found in the lowest layer of the epidermis. Although basal cell carcinoma may not originate in the basal cells, the disease is so named because the cancer cells resemble basal cells. Basal cell carcinoma is the most common human cancer. More than 800,000 people develop this type of cancer in the United States each year. Basal cell carcinoma usually develops on skin surfaces that are exposed to sunlight, commonly on the head or neck.

The tumors usually begin as small, shiny, firm, raised growths (papules) that enlarge very slowly, sometimes so slowly that they go unnoticed as new growths. However, the growth rate varies greatly from tumor to tumor, with some growing as much as ½ inch (about 1 centimeter) in a year.

Basal cell carcinomas can vary greatly in their appearance. Some are raised bumps that may break open and form scabs in the center. Some are flat pale or red patches that look somewhat like scars. The border of the cancer is sometimes thickened and pearly white. The cancer may alternately bleed and form a scab and heal, leading a person to falsely think that it is a sore rather than a cancer.

Basal Cell Carcinoma

Basal cell carcinomas rarely spread (metastasize) to distant parts of the body. Instead, they invade and slowly destroy surrounding tissues. When basal cell carcinomas grow near the eye, mouth, bone, or brain, the consequences of invasion can be serious and can lead to death. Yet, for most people, the tumors simply grow slowly into the skin.

Diagnosis, Treatment, and Prevention

Doctors often can recognize a basal cell carcinoma simply by looking at it, but a biopsy is the standard procedure for confirming the diagnosis (see Diagnosis and Treatment of Skin Disorders: Diagnosis of Skin Disorders).

Doctors remove the cancer in the office by scraping and burning it with an electric needle (curettage and electrodesiccation) or by cutting it out. Also, certain chemotherapy drugs may be applied to the skin. A technique called Mohs microscopically controlled surgery may be required for some basal cell carcinomas that regrow or occur in certain areas, such as around the nose and eyes. Rarely, radiation treatment is used.

Treatment is nearly always successful, and basal cell carcinoma is rarely fatal. However, almost 25% of people with a history of basal cell carcinoma develop a new basal cell cancer within 5 years. Thus, anyone with one basal cell carcinoma should have a yearly skin examination.

Because basal cell carcinoma is often caused by sun exposure, people can help prevent this cancer by staying out of the sun and using protective clothing and sunscreen. In addition, any skin change that persists for more than a few weeks should be evaluated by a doctor.

Mohs Microscopically Controlled Surgery
Because skin cancer cells often have spread beyond the edges of the visible patch on the skin, doctors sometimes use a special surgical technique to make sure they remove all of the cancer. In this technique, called Mohs microscopically controlled surgery or Mohs micrographic surgery, doctors first remove the visible tumor and then begin cutting away the edges of the wound bit by bit. During surgery, doctors examine pieces of tissue to look for cancer cells. Tissue removal from the area continues until the samples no longer contain cancer cells. This procedure enables doctors to limit the amount of tissue removed and thus is especially useful for cancers near such important sites as the eye. After removing all of the cancer, doctors decide how best to replace the skin that has been cut away. They may use a skin graft (see Transplantation: Transplantation of Other Organs) to bring the edges of the remaining skin together with sutures. Or they may place dressings on top of the wound and let the skin heal on its own. Mohs surgery reduces recurrence rates for skin cancers. This surgery is useful for basal cell and squamous cell cancer but is rarely used for melanoma.

Last full review/revision October 2008 by Gregory L. Wells, MD