Describe the clinical appearance of melanoma.

Cutaneous melanoma can have a number of different appearances. Malignant melanomas can begin in a preexisting melanocytic nevus; however, as noted above, the exact percentage of malignant melanomas arising in preexisting nevi versus those arising de novo is controversial. When malignant melanoma arises in a preexisting nevus, the nevus usually demonstrates a change in appearance, such as an increase in size or change in shape, or it may bleed easily when traumatized. A changing nevus is the most important risk factor for melanoma. The development of a new pigmented nevus in any patient over 35 years of age should be evaluated. Classically, early melanoma lesions are characterized by containing different colors, such as different hues of brown, black, red, and blue. Melanoma may also appear as a brown or black discoloration of the nail or as a skin ulcer that does not heal.