A layer of cells in the basal layer of the epidermis, called melanocytes, produces a brown-black skin pigment (melanin) that determines skin and hair color. Melanin also helps protect against the damaging rays of the sun. When cells grow in a controlled manner, the resulting lesion is benign and is commonly referred to as a mole or nevus. Sometimes, however, melanocytes grow out of control and become a cancerous and life-threatening melanoma
. If you see a new mole or a mole that changes its appearance, contact your physician immediately.