While the appearance of any one skin cancer can vary, there are general physical presentations that can be used in screening. Basal cell carcinomas (BCCs) most commonly have a pearly rim or can appear somewhat eczematous. They often ulcerate. Squamous cell carcinomas (SCCs) frequently have a thick keratin top layer. Both BCCs and SCCs are associated with a history of sun-damaged skin. Melanomas are characterized by asymmetry, border irregularity, color variation, a diameter of more than 6 mm, and evolution (ABCDE criteria). Photographs representing typical clinical presentations of these cancers are shown below.