Melanoma (Skin Cancer) Signs, Symptoms, Treatment, Prognosis and Diagnosis on MedicineNet.com

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Melanoma

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Sun-Damaged Skin Slideshow

Skin Changes, How to Spot Skin Cancer

Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

Get information about melanoma. According to the American Academy of Dermatology, one in five Americans will develop some form of skin cancer in their lifetime. Sun exposure is the leading cause of skin cancer, and people with fair skin and light eyes whose skin has a tendency to burn easily in the sun are most susceptible to the damaging effects of the sun�s UV rays. Fortunately, most skin cancers can be detected in their early stages since skin tumors are more visible than tumors of the internal organs.

Three types of cancers account for virtually 100% of skin cancers. The nonmelanomatous skin cancers include basal cell carcinoma and squamous cell carcinoma. Malignant melanoma is the third, and most deadly, type of skin cancer.

Basal cell carcinoma is by far the most common type of skin cancer, accounting for 80% of cases. These slow-growing tumors occur most commonly on areas of the body that are exposed to sun and may take several forms. A raised, reddish, pearly nodule is the most common appearance of basal cell carcinoma, but it may also appear as a pink or red scar or area of irritated skin. Basal cell carcinomas metastasize (spread via the bloodstream or lymphatic channels) very rarely; instead, they grow invasively into surrounding tissues and can cause localized tissue destruction when not completely removed.

Learn to spot the signs of melanoma »

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What is melanoma?

Melanoma is a type of skin cancer. It begins in cells in the skin called melanocytes. 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 against heat, 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, lymph vessels, hair follicles, and glands. Some of these glands produce sweat, which help regulate body temperature. Other glands 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.

Melanocytes and moles

Melanocytes produce melanin, the pigment that gives skin its natural color. When skin is exposed to the sun, melanocytes produce more pigment, causing the skin to tan, or darken.

Sometimes, clusters of melanocytes and surrounding tissue form noncancerous growths called moles. (Doctors also call a mole a nevus; the plural is nevi.) Moles are very common. Most people have between 10 and 40 moles. Moles may be pink, tan, brown, or a color that is very close to the person's normal skin tone. People who have dark skin tend to have dark moles. Moles can be flat or raised. They are usually round or oval and smaller than a pencil eraser. They may be present at birth or may appear later on -- usually before age 40. They tend to fade away in older people. When moles are surgically removed, they normally do not return.