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Basal Cell Carcinoma

By

Gregory L. Wells

, MD, Ada West Dermatology, St. Luke’s Boise Medical Center, and St. Alphonsus Regional Medical Center

Last full review/revision May 2019| Content last modified May 2019
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Basal cell carcinoma, the most common skin cancer, originates in certain cells of the outer layer of the 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 usually removed, but sometimes people may be given chemotherapy drugs applied to the skin or, occasionally, radiation therapy or drug therapy.

Basal cells are in the lowest layer of the epidermis (the outer layer of the skin). Although basal cell carcinoma may not develop from the basal cells, the disease is so named because the cancer cells look like basal cells under a microscope.

Basal cell carcinoma is the most common type of skin cancer. More than 4 million people develop this type of cancer in the United States each year. It is more common among fair-skinned people with a history of sun exposure and is very rare among dark-skinned people. Basal cell carcinoma usually develops on skin surfaces that are exposed to sunlight, commonly on the head or neck.

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

Symptoms

There are several types of basal cell carcinomas.

The nodular type of basal cell carcinoma usually begins as small, shiny, firm, almost clear to pink in color, raised growth. After a few months or years, visible dilated blood vessels (telangiectases) may appear on the surface, and the center may break open and form a scab. 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.

Other types of basal cell carcinomas vary greatly in appearance. For example, the superficial type appears as flat thin red or pink patches, and the morpheaform type appears as thicker flesh-colored or light red patches that look somewhat like scars.

Examples of Basal Cell Carcinoma

Diagnosis

  • Biopsy

Doctors often can recognize a basal cell carcinoma simply by looking at it, but a biopsy is the standard procedure for confirming the diagnosis. During this procedure, doctors remove a piece of the tumor and examine it under a microscope.

Prognosis

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

Prevention

Because basal cell carcinoma is often caused by sun exposure, people can help prevent this cancer by doing the following:

  • Avoiding the sun: For example, seeking shade, minimizing outdoor activities between 10 AM and 4 PM (when the sun’s rays are strongest), and avoiding sunbathing and the use of tanning beds

  • Wearing protective clothing: For example, long-sleeved shirts, pants, and broad-brimmed hats

  • Using sunscreen: At least sun protection factor (SPF) 30 with UVA and UVB protection used as directed and reapplied every 2 hours and after swimming or sweating but not used to prolong sun exposure

In addition, any skin change that lasts for more than a few weeks should be evaluated by a doctor.

Treatment

  • Removal of the tumor (many different methods)

Doctors may remove the cancer in the office by scraping and burning it with an electric needle (a procedure called curettage and electrodesiccation) or by cutting it out. Doctors may destroy the cancer by using extreme cold (cryosurgery).

Certain chemotherapy drugs may be applied to the skin. Photodynamic therapy (see Using Lasers to Treat Skin Problems), in which chemicals and a laser are applied to the skin, also may be used. Occasionally, radiation therapy is used.

A technique called Mohs microscopically controlled surgery may be required for some basal cell carcinomas that are large or regrow or occur in certain areas, such as around the nose and eyes.

People whose cancer has spread to nearby tissues or spread to other parts of the body (metastasized) and who are not candidates for surgery or radiation therapy may be given the drug vismodegib or sonidegib taken by mouth.

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 bring the edges of the remaining skin together with sutures or use a skin graft or skin flap. 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 cancers but is less often used for melanoma.

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