Basal cell carcinoma is a type of skin cancer that arises from the basal cells, which are located in the lower part of the epidermis (outer layer of the skin). It is the most common type of skin cancer, and it typically occurs on areas of the skin that are exposed to the sun, such as the face, neck, and arms. Basal cell carcinoma usually appears as a pearly or waxy bump on the skin, and it may bleed or crust over. Treatment may include surgical removal, radiation therapy, or topical medication, and the choice of treatment depends on the size and location of the cancer. Early diagnosis and treatment are important to prevent the cancer from spreading to other parts of the body.

Basal cell carcinoma occurs when one of the skin's basal cells develops a mutation in its DNA.

Basal cells are found at the bottom of the epidermis — the outermost layer of skin. Basal cells produce new skin cells. As new skin cells are produced, they push older cells toward the skin's surface, where the old cells die and are sloughed off.

The process of creating new skin cells is controlled by a basal cell's DNA. The DNA contains the instructions that tell a cell what to do. The mutation tells the basal cell to multiply rapidly and continue growing when it would normally die. Eventually the accumulating abnormal cells may form a cancerous tumor — the lesion that appears on the skin.

Ultraviolet light and other causes

Much of the damage to DNA in basal cells is thought to result from ultraviolet (UV) radiation found in sunlight and in commercial tanning lamps and tanning beds. But sun exposure doesn't explain skin cancers that develop on skin not ordinarily exposed to sunlight. Other factors can contribute to the risk and development of basal cell carcinoma, and the exact cause may in some cases not be clear.

To reduce your risk of basal cell carcinoma you can:

• Avoid the sun during the middle of the day. In many places, the sun's rays are strongest between about 10 a.m. and 4 p.m. Schedule outdoor activities for other times of the day, even during winter or when the sky is cloudy.
• Wear sunscreen year-round. Use a broad-spectrum sunscreen with an SPF of at least 30, even on cloudy days. Apply sunscreen generously, and reapply every two hours — or more often if you're swimming or perspiring.
• Wear protective clothing. Cover your skin with dark, tightly woven clothing that covers your arms and legs, and a broad-brimmed hat, which provides more protection than does a baseball cap or visor.
• Some companies also sell protective clothing. A dermatologist can recommend an appropriate brand. Don't forget sunglasses. Look for those that block both types of UV radiation — UVA and UVB rays.
• Avoid tanning beds. Tanning beds emit UV rays and can increase your risk of skin cancer.
• Check your skin regularly and report changes to your doctor. Examine your skin often for new skin growths or changes in existing moles, freckles, bumps and birthmarks. With the help of mirrors, check your face, neck, ears and scalp.
• Examine your chest and trunk and the tops and undersides of your arms and hands. Examine both the front and the back of your legs and your feet, including the soles and the spaces between your toes. Also check your genital area and between your buttocks.

The goal of treatment for basal cell carcinoma is to remove the cancer completely. Which treatment is best for you depends on the type, location and size of your cancer, as well as your preferences and ability to do follow-up visits. Treatment selection can also depend on whether this is a first-time or a recurring basal cell carcinoma.

Surgery

Basal cell carcinoma is most often treated with surgery to remove all of the cancer and some of the healthy tissue around it.

Options might include:

• Surgical excision. In this procedure, your doctor cuts out the cancerous lesion and a surrounding margin of healthy skin. The margin is examined under a microscope to be sure there are no cancer cells.
• Excision might be recommended for basal cell carcinomas that are less likely to recur, such as those that form on the chest, back, hands and feet.
• Mohs surgery. During Mohs surgery, your doctor removes the cancer layer by layer, examining each layer under the microscope until no abnormal cells remain. This allows the surgeon to be certain the entire growth is removed and avoid taking an excessive amount of surrounding healthy skin.
• Mohs surgery might be recommended if your basal cell carcinoma has a higher risk of recurring, such as if it's larger, extends deeper in the skin or is located on your face.

Other treatments

Sometimes other treatments might be recommended in certain situations, such as if you're unable to undergo surgery or if you don't want to have surgery.

Other treatments include:

• Curettage and electrodessication (C and E). C and E treatment involves removing the surface of the skin cancer with a scraping instrument (curet) and then searing the base of the cancer with an electric needle.
• C and E might be an option for treating small basal cell carcinomas that are less likely to recur, such as those that form on the back, chest, hands and feet.
• Radiation therapy. Radiation therapy uses high-energy beams, such as X-rays and protons, to kill cancer cells.
• Radiation therapy is sometimes used after surgery when there is an increased risk that the cancer will return. It might also be used when surgery isn't an option.
• Freezing. This treatment involves freezing cancer cells with liquid nitrogen (cryosurgery). It may be an option for treating superficial skin lesions. Freezing might be done after using a scraping instrument (curet) to remove the surface of the skin cancer.
• Cryosurgery might be considered for treating small and thin basal cell carcinomas when surgery isn't an option.
• Topical treatments. Prescription creams or ointments might be considered for treating small and thin basal cell carcinomas when surgery isn't an option.
• Photodynamic therapy. Photodynamic therapy combines photosensitizing drugs and light to treat superficial skin cancers. During photodynamic therapy, a liquid drug that makes the cancer cells sensitive to light is applied to the skin. Later, a light that destroys the skin cancer cells is shined on the area.
• Photodynamic therapy might be considered when surgery isn't an option.

Treatment for cancer that spreads

Very rarely, basal cell carcinoma may spread (metastasize) to nearby lymph nodes and other areas of the body. Additional treatment options in this situation include:

• Targeted drug therapy. Targeted drug treatments focus on specific weaknesses present within cancer cells. By blocking these weaknesses, targeted drug treatments can cause cancer cells to die.
• Targeted therapy drugs for basal cell carcinoma block molecular signals that enable the cancers to continue growing. They might be considered after other treatments or when other treatments aren't possible.
• Chemotherapy. Chemotherapy uses powerful drugs to kill cancer cells. It might be an option when other treatments haven't helped.