What is melanoma? Melanoma is a common cancer of the skin. Melanoma, also known as malignant melanoma, is the most deadly type of skin cancer because it can spread quickly (metastasize) to other organs of the body. The incidence of melanoma is growing faster than any other type of cancer, primarily because of the popularity of sunbathing and the use of tanning beds. Melanoma arises in the skin cells that make melanin, the pigment that produces skin color. Normally, when these cells are old or damaged, they stop dividing and die and are replaced by healthy young cells. Melanoma occurs when old or damaged cells continue to divide and multiply uncontrollably. This results in the development of a malignant mass of tissue (tumor) on the skin. Melanoma can develop in an existing pigmented skin lesion, such as a mole or a freckle, or within normal-appearing skin as well. Melanoma is often preventable by protecting your skin from sunburn and excessive sun exposure. In some cases, melanoma can develop anywhere on the body, even places that are not exposed to sun and sunburns. Left untreated, melanoma cancer cells can continue to multiply and spread from the skin to other parts of the body such as the lymph nodes. Melanoma can lead to life-threatening complications and be fatal. If you notice any changes in your skin or in the color, shape or texture of a mole, seek prompt medical care. Early diagnosis and treatment increase the chances that melanoma will be discovered in its earliest, most curable stage.