Most melanomas begin in a mole or other pre-existing skin lesion.
It appears rarely in the eye, mouth, vagina or anus. Its borders are often irregular and may bleed. When the cells grow down into deep skin layers, they invade blood vessels and lymph vessels and are spread to other body areas. Occupations or activities involving excessive sun exposure, such as farming, construction work, athletics or sunbathing. This is most common in light-complexioned, blonde people.