Basal cell carcinoma is a cancer that originates in cells of the epidermis.

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 1 million 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 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. Yet, for most people, the tumors simply grow slowly into the skin.

Diagnosis, Treatment, and Prevention

A doctor 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).

A doctor removes the cancer in the office by scraping and burning it with an electric needle (curettage and electrodesiccation) or by cutting it out. 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, in almost 25% of people who have been treated successfully, another basal cell carcinoma develops within 5 years. Thus, anyone with one basal cell carcinoma should have yearly skin examinations.

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. While they are still performing surgery, doctors examine pieces of tissue immediately to look for cancer cells. Tissue removal from the area continues until the samples no longer contain cancer cells. Mohs' surgery is useful for basal cell and squamous cell cancer. The procedure limits the amount of tissue removed, which is especially important for cancer near important sites such as the eye. Mohs' surgery also reduces recurrence rates for skin cancers. It is rarely used for melanoma. After removing all of the cancer, the surgeon decides how best to replace the skin that has been cut away. The surgeon may decide to use a skin graft (see Transplantation: Transplantation of Other Organs), to bring the edges of the remaining skin together with sutures, or to let the skin heal on its own with dressings placed on top of the wound.

Last full review/revision February 2003