What is Melanoma?

Skin cancer is the most common type of cancer in the United States, and melanoma may the most well-known type. And although melanoma is the least common form of skin cancer, it is the most aggressive.

It is also one of most survivable cancers when found and treated early. For this reason, it’s important to know the risk factors for all types of skin cancer and how to recognize the signs that should prompt you to consult your doctor. There are no recommended routine screening tests for skin cancer as there are for other types of cancer, but you can do a lot to protect your health by learning how to do regular examinations on your skin.

Anatomy Of The Skin

The skin is the body’s largest organ and the first line of defense against infection and injury. It forms a porous barrier between the body’s internal structures and organs and the outside environment. The skin helps to regulate the body’s temperature, provides protection from the elements, and wards off harmful microorganisms.

The skin is made up of two main layers: the epidermis and the dermis.

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The epidermis is the outermost layer of skin. It consists mostly of flat cells called squamous cells, which make up the thickest part of the epidermis. Beneath these cells are round basal cells. In the deepest part of the epidermis are found melanocytes, which produce the pigment that gives skin its color.

Under the epidermis lies the dermis, where blood and lymph vessels are found. Also in this layer are sweat and oil glands. Sweat cools the skin surface, and an oily substance called sebum keeps the skin from drying out. Sweat and oil released by glands in the dermis reach the skin surface through tiny, tunnel-like holes called pores.

How Melanoma Starts

Melanoma arises in melanocytes, the cells in the epidermis that produce melanin and give skin its color. When skin is exposed to the sun, melanocytes produce more of this pigment, causing the skin to darken. Sometimes a number of melanocytes, along with surrounding tissue, cluster together to form dark spots, or moles.

Melanoma occurs when cancerous changes take place in melanocytes, causing them to become malignant (capable of spreading).

Types of Melanoma

Most melanocytes are located in the skin. Melanoma that occurs in the skin is called cutaneous melanoma. Melanoma can also occur in the eye, where it is known as ocular melanoma or intraocular melanoma. Very rarely, melanoma arises in other areas of the body, including the meninges (the tissue that lines the spinal cord), the digestive tract, and the lymph nodes.

Key Statistics

Melanoma accounts for about 3 percent of all cases of skin cancer, but causes most skin cancer deaths. An estimated 62,480 new cases of melanoma will be diagnosed in the United States in 2008, and more than 8,000 persons will die of the disease. The 5-year survival rate—the percentage of people who live for at least 5 years after diagnosis—for melanoma is 92 percent.