Melanoma is the most lethal skin cancer, although it can be easily cured if caught early enough. It is named for the skin cell from which it arises, called the melanocyte , which produces a brown-black skin pigment called melanin . Melanin helps to protect against the damaging rays of the sun and to determine skin coloring. When cell proliferation occurs in a controlled and contained manner, the resulting lesion is benign and is commonly referred to as a mole or nevus .
Most adults have at least several dozen benign moles.
Sometimes, however, pigment cells grow out of control and become malignant and life-threatening melanoma. Early detection of melanoma is critical because of the skin's unique anatomy. The outermost layer of the skin, the epidermis , is only about 20 cells, roughly as thick as a sheet of paper. The dermis contains tiny blood and lymph vessels, which increase in number deeper in the skin. Pigment cells, the melanocytes, are found in the transitional layer between the epidermis and dermis.