Melanoma is a skin cancer that arises in cells called melanocytes—cells that make the brown pigment called melanin.

Melanoma appears as a pre-existing mole that changes, or as a new mole on previously unaffected/clear skin."
According to histopathological studies, about 20% to 40% of melanomas arise in association with a dysplastic nevus, and between 2.5% to 8% arise in association with a congenital nevus. 

Melanoma is a potentially lethal skin cancer, with a higher fatality rate than basal cell cancer and squamous cell cancer.

An estimated 51,400 new cases of melanoma will be diagnosed in the year 2001 in the United States.

As of 2001, an estimated 7,800 people will likely die of melanoma every year in the United States.

More than 80% of skin cancer deaths are from melanoma

Melanoma can arise at any age but most commonly occurs after puberty.

Melanoma is the sixth most common cancer in men and the seventh most common in women.

When melanoma is detected at its early stage, surgical removal cures the disease in most cases. If the disease has spread to lymph nodes, the 5-year survival rate is 30-40%. If the disease has spread to distant organs (liver, bones, brain, etc.) the 5-year survival rate is 12%.

Genetic factors are the most important of the known risk factors, including the familial tendency to develop melanoma, prominent moles, and atypical moles.

Overexposure to ultraviolet radiation in sunlight is believed to be a contributing factor to some cases of melanoma; short periods of intense exposure, such as sunbathing is associated with a 2-fold increase in melanoma risk.