Melanoma

What is melanoma?

Melanoma is a type of skin cancer. It begins in certain cells in the skin called melanocytes. Each year more than 53,600 people in the United States find out they have melanoma. To understand melanoma, it is helpful to know about the skin and about melanocytes, what they do, how they grow, and what happens when they become cancerous.

THE SKIN

The skin is the body's largest organ. It protects us against sunlight, injury, and infection. It helps regulate body temperature, stores water and fat, and produces vitamin D. The skin has two main layers: the outer epidermis and the inner dermis.

The epidermis is mostly made up of flat, scalelike cells called squamous cells. Round cells called basal cells lie under the squamous cells in the epidermis. The lower part of the epidermis also contains melanocytes.

The dermis contains blood vessels, lymphatic vessels, hair follicles, and glands. Some of these glands produce sweat, which help regulate body temperature, and some produce 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.

Healthy cells that make up the skin normally grow, divide, and replace themselves in an orderly way as the body needs them. This helps keep the skin in good repair.

MELANOCYTES AND MOLES

Melanocytes are spread throughout the lower part of the epidermis. They produce melanin, the pigment that gives our skin its natural color. When skin is exposed to the sun, melanocytes produce more pigment, causing the skin to tan, or darken.

Sometimes, melanocytes grow in a cluster. Benign (not cancerous) clusters of melanocytes are called moles. (Doctors also call a mole a nevus; the plural is nevi). Moles are very common. Most people have between 10 and 40 of these brown, tan, or black areas on the skin. Moles can be flat or raised. They are usually round or oval and smaller than a pencil eraser. They can be present at birth or appear later, usually before age 40. Moles generally grow or change only slightly over a long period of time. They tend to fade away in older people. When moles are surgically removed, they normally do not return.

CANCER

Cancer is a group of diseases with one thing in common: cells become abnormal, dividing too often and without control or order. These malignant (cancerous) cells form a tumor and can invade and destroy nearby tissue. The cancer cells can also spread through the lymphatic system or the bloodstream to other parts of the body and form new tumors. The spread of cancer is called metastasis




MELANOMA



Melanoma occurs when melanocytes become malignant. The disease is also referred to as cutaneous melanoma or malignant melanoma. (Another type of melanoma, ocular melanoma, develops in the eye and is not discussed here).
Melanoma can occur on any skin surface. In men, it is often found on the trunk (the area from the shoulders to the hips) or the head and neck. In women, melanoma often develops on the lower legs or the trunk. Melanoma is rare in black people and others with dark skin. When it does develop in dark-skinned people, it tends to occur under the fingernails or toenails, or on the palms or soles. Melanoma affects people of all age groups, but the chance of developing this disease increases with age.