Melanoma is a cancer of the pigment producing cells in the skin, known as melanocytes. Cancer is a condition in which one type of cell grows without limit in a disorganized fashion, disrupting and replacing normal tissues and their functions, much like weeds overgrowing a garden. Normal melanocytes reside in the outer layer of the skin and produce a brown pigment called melanin, which is responsible for skin color. Melanoma occurs when melanocytes become cancerous, grow, and invade other tissues.
Melanoma is a malignant tumor of melanocytes which are found predominantly in skin but also in the bowel and the eye (see uveal melanoma). It is one of the rarer types of skin cancer but causes the majority of skin cancer related deaths. Malignant melanoma is a potentially serious type of skin cancer. It is due to uncontrolled growth of pigment cells, called melanocytes. Despite many years of intensive laboratory and clinical research, the sole effective cure is surgical resection of the primary tumor before it achieves a thickness greater than 1 mm.
Symptoms of Malignant Melanoma
The primary symptom of any skin cancer is usually a mole, sore, lump, or growth on the skin. Any change in appearance of a pigmented skin lesion over time is a warning sign. Also, watch for any bleeding from a skin growth.
Normal moles are generally a uniform color, such as tan, brown or black, with a distinct border separating the mole from your surrounding skin. They're oval or round in shape and about 1/4 inch (6 millimeters) in diameter — the size of a pencil eraser.
In men, melanoma most often occurs on the trunk. In women, melanoma is most 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 melanoma on the palms of the hands and the soles of the feet.
Melanoma usually begins as an abnormal mole. To distinguish a normal mole from a melanoma, skin disease specialists (dermatologists) have developed the ABCD rule. According to this guide, the following features characterize melanoma:
Asymmetry - an odd shape, or one half is shaped differently from the other
Border—The edges are often ragged, notched, blurred, or irregular in outline; the pigment may spread into the surrounding skin.
Color - different shades of black, brown, and tan in the same mole; there may also be patches of white, gray, red, pink, or blue in it
Diameter—There is a change in size, usually an increase. Melanomas are usually larger than the eraser of a pencil (1/4 inch or 5 millimeters).
Causes of Malignant Melanoma
When a melanocyte becomes malignant, it begins to proliferate uncontrollably. Melanoma can arise in an existing mole, or it can arise de novo, that is, by itself in otherwise unblemished skin.
UVB light causes harmful changes in skin cell DNA, including the development of oncogenes — a type of gene that can turn a normal cell into a cancerous one. But UVA light may be more likely to damage melanocytes, leading to melanoma. Tanning lamps and beds mainly produce UVA radiation.
Fair skin people seem to be at greater risk for developing melanoma than darker skinned people. Excessive sun exposure, especially if burning occurs during childhood, may increase the risk of getting melanoma.
Ethnic origin - Caucasians are 10 times more likely than African-Americans to develop melanoma. The risk to Caucasians increased by 50 percent between 1950 and 1980. People with the fairest skin are at the highest risk.
