The most serious type of skin cancer, develops in the cells (melanocytes) that produce melanin — the pigment that gives your skin its color. Melanoma can also form in your eyes and, rarely, in internal organs, such as your intestines.
A change in an existing mole
The development of a new pigmented or unusual-looking growth on your skin
Melanoma doesn't always begin as a mole. It can also occur on otherwise normal-appearing skin.