Melanoma is a type of cancer that is formed from melanocytes. Although melanoma accounts for about 1% of all cases of skin cancer, it is responsible for most deaths from skin cancer. Other common types of skin cancer include basal cell carcinoma and squamous cell carcinoma.

Melanoma can occur anywhere where melanocytes are present. Most melanocytes are in the skin; therefore, most melanomas are found on the surface of the skin, which includes the nail bed, the soles, and the scalp. However, melanoma can also occur in the eye (uveal melanoma) or on the inner surfaces of the mucosa, including the mucous membranes that make up the sinuses, the anal canal, the rectum, and the vagina.