Basal cell carcinoma
Basal Cell Carcinoma
A basal cell carcinoma is a skin cancer that originates from basal keratinocytes in the top layer of the skin, the epidermis. Sometimes these tumors are called "rodent ulcers."
Basal keratinocytes are unpigmented skin cells found deep in the epidermis, hair follicles, and sweat glands. When they become cancerous, these cells invade the dermis (the layer of skin just below the epidermis) and spread out into the normal skin. They become visible as a small growth or area of change in the skin's appearance. These tumors can appear anywhere on the body, but most become evident on the face and neck.
Most basal cell carcinomas are small tumors that can be cured with simple surgeries. They usually grow quite slowly. However, neglected or aggressive tumors can invade vast amounts of skin. These cancers can also spread along bones, cartilage, muscles, and, more rarely, nerves. Some tumors may eventually reach the eye or brain or become large enough to significantly disfigure the face. These serious consequences are more likely if the tumor lies close to bone and cartilage—for instance, at the corner of the eye. Very few basal cell carcinomas spread to more distant organs; no more than five out of every 10, 000 of these tumors metastasize. Most that do are very large, deep cancers that have been visible for years.
Basal cell carcinomas are most common from middle age until old age. They are more frequent in men than women. These cancers seem to be associated with exposure to ultraviolet light; they tend to develop on sun-exposed areas and are more common in people living near the equator. Those who have lighter skin are more susceptible; fair-haired blonds are more likely to develop tumors than people with darker complexions. In the United States, Caucasians have a 28% to 33% chance of developing a basal cell carcinoma over a lifetime.
Weakened immunity may also play a role. Those who have had an organ transplanted or who have contracted acquired immune deficiency syndrome (AIDS) are more likely to develop one of these cancers.
Basal cell carcinomas are particularly common among individuals with a rare genetic disease called nevoid basal cell carcinoma syndrome (Gorlin's syndrome). Individuals with this disease can be born with basal cell carcinomas or begin to develop them in childhood. Some have few or no cancers; others have more than 250. These tumors seldom grow much before puberty, but during and after adolescence they can spread rapidly. Other symptoms include small pits in the palms and soles, cysts in the jaw, and other abnormalities in the bones.
Causes and symptoms
Basal cell carcinomas are caused by genetic damage to a skin cell. Exposure to ultraviolet light and x rays, suppression of the immune system, and genetic factors seem to increase the risk that this will happen. The exact cause, however, is rarely known.
Several types of basal cell carcinomas exist. Nodular basal cell carcinomas are the most common form. These tumors begin as a tiny red or clear bump on the skin. Over time, they develop into a growth with clear or white "pearly" raised edges and, often, a depressed area in the middle. A network of tiny blood vessels usually crisscrosses the surface, and the tumor may bleed repeatedly or crust over. Morpheaform (sclerosing, morpheic) basal cell carcinomas are more difficult to detect. These tumors are usually pale, firm, flat growths that can blend into the normal skin around them. Many look just like a scar. Superficial basal cell carcinomas are flat, red, scaly plaques that can look like psoriasis or eczema. Unlike other basal cell carcinomas, they are usually found on the arms, legs, and torso. Pigmented basal cell carcinomas are brown, black, or blue; they are usually of the nodular type and can look like a melanoma .
Some general characteristics of skin cancers include:
- irregular or ragged borders
- non-symmetrical shape
- a change in color
- a size greater than 0.2 inches (6 mm)
Basal cell carcinomas are usually diagnosed with a skin biopsy taken in the doctor's office. This is generally a brief and simple procedure. After numbing the skin with an injection of local anesthetic, the doctor snips out a tiny piece of the tumor. The skin sample must be sent to a trained pathologist to be analyzed. It may take up to a week for the biopsy results to come back. Sometimes the tumor is removed immediately after the biopsy, before the results are known.
Primary care physicians remove some basal cell carcinomas; other cancers, including larger or more complicated tumors, may be referred to a dermatologist. The services of a plastic surgeon are occasionally necessary. In the rare event that a tumor metastasizes, an oncologist and full cancer treatment team become involved.
Clinical staging, treatments, and prognosis
Basal cell carcinomas very rarely spread into the lymph nodes and internal organs. For this reason, doctors tend not to stage them. If staging is needed, the TNM (tumor, lymph node, and metastases) system is usually used. For basal cell carcinomas, this can be simplified into the following five categories:
- Stage 0: The cancer is very small and has not yet spread from the epidermis to the dermis.
- Stage 1: The cancer is less than 2 cm (0.8 inches) in diameter. No cancer cells can be found in lymph nodes or other internal organs.
- Stage 2: The cancer is more than 2 cm (0.8 inches) in diameter. No cancer cells can be found in lymph nodes or other internal organs.
- Stage 3: Cancer cells have been found either in nearby lymph nodes or in the bone, muscle, or cartilage beneath the skin (or in both locations).
- Stage 4: Cancer cells have been discovered in internal organs, most often the lungs or lymph nodes, that are distant from the skin. A stage four cancer can be any size.
Treatment options for non-metastatic, non-staged tumors
For most tumors—non-metastatic, non-staged cancers—there may be several treatment options. Which treatment is recommended depends on the size and type of tumor, its location, and cosmetic considerations. The cure rates for most of the following techniques are approximately 85% to 95%, but vary with tumor size and other factors. Mohs' micrographic surgery has a five-year cure rate of 96%. Success rates for recurrent tumors are approximately 50% with most techniques and 90% with Moh's surgery .
In conventional surgery, the doctor numbs the area with an injection of local anesthetic, then cuts out the tumor and a small margin of normal skin around it. The wound is closed with a few stitches. One advantage to conventional surgery is that the wound usually heals quickly. Another benefit is that the complete cancer can be sent to a pathologist for evaluation. If the skin around the tumor is not completely free of cancer cells, the tumor can be treated again immediately.
Mohs' micrographic surgery is a variation of conventional surgery. In this procedure, the surgeon examines each piece of skin under the microscope as it is removed. If any cancer cells remain, another slice is taken from that area and checked. These steps are repeated until the edges of the wound are clear of tumor cells, then the wound is closed. The advantage to this technique is that all of the visible cancer cells are removed but as much normal skin as possible is spared. Mohs' surgery is often used for larger or higher risk tumors and when cosmetic considerations are important. The main disadvantage is that it takes much longer than conventional surgery and requires a specially trained surgeon.
A laser is sometimes used as a cutting instrument instead of a scalpel. Laser light can also destroy some cancer cells directly. A disadvantage to laser surgery is that the wounds from some lasers heal more slowly than cuts from a scalpel. The advantage is that bleeding is minimal.
In electrodessication and curettage, the physician scoops out the cancer cells with a spoon-shaped instrument called a curette. After most of the tumor is gone, the remaining cancerous tissue is destroyed with heat from an electrical current. The wound is left open to heal like an abrasion. It leaks fluid, crusts over, and heals during the next two to six weeks. This is a safe and easy method for removing many basal cell carcinomas. One disadvantage is that there is no skin sample to confirm that the tumor is completely gone. The electrical current used during this surgery can interfere with some pacemakers and larger tumors may heal with a noticeable scar.
In cryosurgery, liquid nitrogen is used to freeze the tumor and destroy it. This treatment is another type of blind destruction; there is no skin sample to make sure the cancer cells have all been killed. Patients report swelling and pain after cryosurgery, and a wound appears a few days later where the cells were destroyed. When the site heals, it has usually lost its normal pigment. There is a risk of nerve damage with this technique.
Radiation therapy is an uncommon treatment for basal cell carcinoma. One disadvantage is the inconvenience: multiple treatments, over a period of weeks, are necessary. Tumors that return after radiation also tend to grow more quickly than the original cancer. In addition, x rays may promote new skin cancers. Radiation therapymay be an option for patients who cannot undergo even minor surgery. It is also used occasionally as an adjunct to surgery. One advantage is that the cosmetic results can be very good.
Occasionally a lotion containing fluorouracil is applied to the tumor. This drug cannot penetrate very far and cancer cells in the deeper parts of the tumor may not be destroyed. The main advantage to this treatment is its simplicity.
Treatment options for metastatic cancers
Cancers that have spread to internal organs are treated with a combination of surgery, radiation, and chemotherapy .
The prognosis for small, uncomplicated basal cell carcinomas is very good. The vast majority of these tumors can be successfully removed. However, cancers that were not completely destroyed may regrow. If the edges of the removed skin contain cancer cells, the chance that the tumor will return within the next five years is about 40%. Regrowth is more likely with cancers larger than 0.8 inches (2 cm), those on the face (particularly around the nose, eye, and ear), and higher risk types such as morpheaform tumors. Tumors can redevelop in the scar from the surgery, on the edges of the surgery site, or deep in the skin. These cancers may not look like the original tumor. Patients should be particularly watchful for minor changes in the appearance of the scar or sores that appear nearby.
Cancers that metastasize spread most often to the lymph nodes and lungs. The prognosis for metastatic cancers is poor, even with treatment. Survival after spread of the cancer to internal organs is eight months on the average and seldom more than a year and a half.
Coping with cancer treatment
Most basal cell carcinomas are removed with techniques that cause few, if any, lasting side effects. Patients who have cosmetic concerns may wish to discuss them with their doctor.
In photodynamic laser therapy, a dye activated by laser light destroys the cancer. This dye is spread onto the skin, injected, or drunk. During a waiting period, normal cells clear the dye, then a laser activates the remainder. As of 2001, this technique was only useful for cancers very near the surface of the skin. One side effect after treatment is a period of excessive sun-sensitivity. Several clinical trials are in progress.
In 1999, researchers first reported that imiquimod 5% cream, spread onto the skin several times a week, could destroy small nodular or superficial basal cell carcinomas. The side effects from this treatment were mainly local skin reactions such as itching , rashes, and redness. Ongoing studies are promising.
Interferon alpha injected into the tumor is sometimes effective for basal cell carcinomas. This experimental treatment is mainly used for less dangerous forms such as the nodular type.
Retinoids, drugs related to vitamin A, may have some effect on basal cell carcinomas. These drugs are taken internally and can have significant serious side effects.
The risk factors for basal cell carcinoma include:
- ethnic background
- geographic location
- increasing age
- exposure to x rays and ultraviolet light (both UVA and UVB)
- a history of premalignant skin lesions or skin cancer
- genetic disorders such as nevoid basal cell carcinoma syndrome, xeroderma pigmentosum, and albinism
- suppression of the immune system by AIDS or an organ transplant
Some important preventative steps are to wear protective clothing and hats in the sun, use a sunscreen, avoid the sun between 10 A.M. and 4 P.M., and stay away from suntanning booths. Checking the skin for early signs of cancer is also critical.
Drugs related to vitamin A (including beta-carotene, retinol, and isotretinoin), vitamin E, nonsteroidal anti-inflammatory drugs (NSAIDS), and selenium might be able to prevent basal cell carcinoma. As of 2001, their effectiveness was still in question.
Because many basal cell carcinomas are found on the face and neck, cosmetic concerns are a priority for many patients. If there is a risk of noticeable scarring or damage, a patient may wish to ask about alternative types of removal or inquire about the services of a plastic surgeon.
After treatment, it is important to return to the doctor periodically to check for regrowth or new skin cancers. Approximately 36% of all patients find a new basal cell or squamous cell carcinoma within the next five years. Having a basal cell carcinoma before the age of 60 may also increase the chance of developing other cancers in internal organs.
See Also chemoprevention; familial cancer syndromes; reconstructive surgery
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Anna Rovid Spickler, D.V.M., Ph.D.
—A genetic disease characterized by the absence of the normal skin pigment, melanin.
—A sample of an organ taken to look for abnormalities. Also, the technique used to take such samples.
—A layer of skin sandwiched between the epidermis and the fat under the skin. It contains the blood vessels, nerves, sweat glands, and hair follicles.
—The thin layer of skin cells at the surface of the skin.
—A cancer drug.
—The structures in the skin that make each hair.
—A drug, approved by the FDA to treat warts, that may destroy basal cell carcinomas by stimulating the immune system. Also known by its trade name Aldara.
—A chemical made naturally by the immune system and also manufactured as a drug.
—A liquid used to numb a small area of the skin.
—A small organ full of immune cells, found in clusters throughout the body. Lymph nodes are where reactions to infections usually begin.
Nonsteroidal anti-inflammatory drugs (NSAIDS)
— A class of drugs that suppresses inflammation. Includes a wide variety of drugs, including aspirin.
—A doctor who specializes in the treatment of cancer.
—A doctor who specializes in examining cells and other parts of the body for abnormalities.
Premalignant skin lesion
—An abnormal change in the skin that has a good chance of turning into skin cancer but is not yet cancerous.
—A mineral needed in extremely small quantities by the body. Large amounts can be very toxic.
Squamous cell carcinoma
—A type of skin cancer.
—Tiny glands scattered throughout the skin that produce sweat.
—A commonly used staging system that examines the main tumor (T), the lymph nodes (N), and metastases (M).
—A genetic disease characterized by the inability to repair damaged DNA. Individuals with this disease develop an excessive number of skin cancers.
QUESTIONS TO ASK THE DOCTOR
- What treatment(s) would you recommend for my tumor?
- How effective would you expect each of them to be, for a tumor of this size and in this location?
- How much cosmetic damage am I likely to see with each treatment?
- Are there any alternatives?
- How should I prepare for the procedure?
- What is the risk that my tumor in particular will regrow?