What Is Melanoma?

Melanoma is a rare but potentially serious type of skin cancer. Skin cancer is a disease in which skin cells lose the ability to divide and grow normally. These abnormal skin cells can grow and form a mass or "tumor."

A skin tumor is considered benign (not cancer) if it is limited to a few cell layers and does not invade surrounding tissues or organs. If the tumor spreads to surrounding tissues, it is considered malignant, or cancerous. Cancer cells crowd out and destroy nearby healthy cells, forming growths called malignant tumors.

Most skin growths are benign tumors. However, melanoma is a malignant skin growth because it can metastasize, which means it can spread to other parts of the body.

Melanoma that spreads to vital organs like the brain or liver can be life-threatening. Fortunately, malignant melanoma has a very high cure rate if diagnosed early and treated promptly.

Types Of Skin Cancer

There are three layers of skin:

• The epidermis, or outer layer of skin, which is made up of three different types of cells

• The dermis, or middle layer of the skin; it contains nerves, blood vessels, sweat glands, hair follicles, and oil-producing cells that keep the skin from drying out

• The fatty layer

Skin cancer can begin in any of the three types of cells that make up the epidermis. Each type of skin cancer is named for the kind of cell that becomes malignant.

• Basal cell carcinoma starts in basal cells, which are small, round cells found at the base of the epidermis. It is the most common kind of skin cancer. More than 90 percent of all skin cancers in the United States are basal cell carcinomas. Basal cell carcinoma is the least serious kind of skin cancer because it grows slowly and seldom spreads.

• Squamous cell carcinoma starts in squamous cells, which are flat scaly cells that form the outermost part of the skin. Squamous cell carcinoma is more serious because it spreads more often than basal cell carcinoma. However, squamous cell carcinoma usually spreads slowly.

• Melanoma starts in the melanocytes, which are pigment-producing cells found mainly in the lower part of the epidermis (the outer layer of the skin). They make a dark material, melanin, which gives skin its natural color. Melanoma is serious because the malignant cells tend to spread rapidly from the skin to internal organs.

Although most pigment-producing cells are in the skin, some of these types of cells occur in other parts of the body and can also become malignant. For example, ocular melanoma begins in the eye. Although it is rare, melanoma also can start in the gastrointestinal tract, lymph nodes, brain, and other areas of the body.

About Moles

Moles are small, usually dark skin growths composed of a group of cells called melanocytes. These cells make the pigment melanin. Moles are very common. The average adult has about 40 to 60 moles and other skin growths.

Moles often are black, brown, or tan. They usually are no bigger than a pencil eraser and are round or oval in shape. Moles may be flat or raised. They may be present at birth or develop during childhood, and almost all are present by age 40.

The medical name for a mole is a nevus. Several moles are called nevi.

Certain kinds of moles called dysplastic nevi, or atypical moles, are typically bigger than ordinary moles. To a doctor, they look different than regular moles. They may appear on sun-exposed areas of the skin, or on areas that get little sunlight, like the buttocks or scalp. Dysplastic nevi tend to run in families. Individuals who have dysplastic nevi are at a greater risk of developing malignant melanoma, especially if they have a positive family history of melanoma.

The average person has dozens of moles and other benign skin growths. They include:

• Birthmarks, or "nevi," are moles that are present at birth.

• Acquired moles begin to develop early in adolescence, growing and darkening throughout the teenage years. Many adults have 40 to 60 acquired moles.

• Liver spots, or "solar lentigines," are flat tan-to-brown spots that occur mainly on the face, neck, hands, and forearms. They have nothing to do with the liver. Rather, they develop as a result of aging and sun exposure.

• Seborrheic keratoses are raised, wart-like, tan-to-brown growths that occur as people age.

• Acquired cherry angiomas are smooth, dome-shaped red spots that usually develop on the chest and back. Most are bright red and appear as people age.

• Skin tags are small, soft flaps of skin that grow on the neck, in the armpits, and groin area.

• Actinic keratoses are slightly scaly, reddish patches that form on people with sun-damaged skin. They are pre-cancerous growths that may change into a squamous cell carcinoma, so doctors usually recommend having them removed.

Although most skin growths are not cancer, it's important to check with the doctor about new growths or changes in old growths. In many cases, the first sign of skin cancer is a mole that changes in size or color, or becomes a sore that does not heal.