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Weighing about 6 pounds, the skin is the body's largest organ. It protects us against heat, light, injury, and infection. It helps regulate body temperature and stores water, fat, and vitamin D. It is made up of two main layers: the outer epidermis and the inner dermis.

The epidermis (outer layer of skin) is mostly made up of flat, scale-like cells called squamous cells. Under the squamous cells are round cells called basal cells. The deepest part of the epidermis also contains melanocytes. These cells produce melanin, which gives the skin its color. The dermis (inner layer of skin) contains blood and lymph vessels, hair follicles, and glands. These glands pro- duce sweat, which helps regulate body temperature, and sebum, an oily substance that helps keep the skin from drying out. Sweat and sebum reach the skin's surface through tiny openings called pores.

What Is Cancer?

Cancer is a group of more than 100 diseases. Although each kind differs from the others in many ways, every cancer is a disease of some of the body's cells. Healthy cells that make up the body's tissues grow, divide, and replace themselves in an orderly way. This process keeps the body in good repair. Sometimes, however, certain cells lose the ability to limit and direct their growth. They divide too rapidly and grow without any order. Too many cells are produced, and tumors begin to form. Tumors can be benign or malignant.

Benign tumors are not cancer. They do not spread to other parts of the body and are seldom a threat to life. Often, benign tumors can be removed by surgery, and they are not likely to return. Malignant tumors are cancer. They can invade and destroy nearby healthy tissues and organs. Cancer cells also can spread, or metastasize, to other parts of the body and form new tumors.

Cancer that develops in melanocytes (the pigment cells) is called melanoma. It may also be called cutaneous melanoma or malignant melanoma. (Another type of melanoma develops in the eye. It is called ocular melanoma.

Melanoma is a very serious disease because it may spread to other parts of the body through the lymphatic system. This system is made up of a network of thin tubes that branch, like blood vessels, into all the tissues of the body. Cancer cells break off from the primary tumor and are carried along by lymph, a colorless, watery fluid that contains infection-fighting cells. Along this network of vessels are groups of small, bean-shaped organs called lymph nodes. Clusters of lymph nodes are found in the underarms, groin, neck, and abdomen. Surgeons often remove lymph nodes to find out whether they contain cancer cells. Melanoma also can spread through the bloodstream. Two other types of skin cancer, basal cell cancer and squamous cell cancer, are much more common. These skin cancers are less serious than melanoma because they rarely spread.

Symptoms

Often, the first sign of melanoma is a change in the size, shape, or color of a mole. A normal mole is a brown, tan, or black spot on the skin. It can be flat or raised, and its shape can be round or oval. Usually, moles are small, less than the size of a pencil eraser. A mole may be present at birth, or it may appear later on-usually in the first 10 years of a person's life. Most moles fade away in older people.

Most people have between 10and3O moles on their body. The vast majority of these moles are perfectly harmless. However, a change in a mole is a sign that you should see your doctor. Thinking of "ABCD" can help you remember the signs of melanoma:

1. Asymmetry-The shape of one half does not match the other.
2. Border-The edges are ragged, notched, or blurred.
3. Color-The color is uneven. Shades of black, brown, or tan are present. Areas of white, red, or blue may be seen.
Diameter-There is a change in size.

Other signs of melanoma may include scaling, oozing, or bleeding of a mole or a change in the way a mole feels; it may become hard, lumpy, itchy, swollen, or tender. Melanoma may also appear like a new mole on the body.

Detection and Diagnosis

Detection

Melanoma in men occurs most often on the trunk (the area between the shoulders and hips) or head and neck. In women, melanoma is often found on the arms and lower legs. It is found most often in people with fair skin. African Americans and people with dark skin are more likely to have melanomas on the palms of the hands and the soles of the feet.
Any health problem should be diagnosed and treated as early as possible, and this is especially true for melanoma. The earlier melanoma is detected, the better a person's chances for a full recovery. People should check their skin regularly for new growths or other changes.

New growths or any changes in moles should be reported to the doctor without delay. Anyone who has already had melanoma should be especially sure to have regular medical exams so that the doctor can check to see that it hasn't returned.

In some families, individuals have unusual moles called dysplastic nevi, which may turn into melanoma much more frequently than do normal moles. People with dysplastic nevi may have more than I 00 moles. These people are at increased risk of developing melanoma and should have regular check- ups to detect problems early.

Diagnosis

Because melanoma can spread, it is important for the doctor to find out as early as possible whether a suspicious- looking area is cancer. The sooner melanoma is found, the sooner the doctor can begin treatment to control the disease.

A biopsy is the only way to make a definite diagnosis. For this test, the doctor removes part or all of the growth. This can usually be done in the doctor's office using local anesthesia. To check for cancer cells, a pathologist or a dermatologist examines the tissue under a microscope. If melanoma is found, the doctor needs to determine the extent, or stage, of the disease. The stage of the disease is based on the thickness of the tumor, the depth of skin penetration, and whether the cancer has spread (metastasized) to nearby lymph nodes or distant parts of the body. Staging is important in planning treatment.

Treating Melanoma

The doctor considers a number of factors to determine the best treatment for melanoma. Among these are the location, size, and depth of the tumor. In addition, the doctor considers where the cancer may have spread, as well as the age and general health of the patient. Before starting treatment, the patient might want a second doctor to review the diagnosis and suggested treatment.