Atypical Nevi, Clark and Dysplastic Nevi Clinical Presentation
AN may appear during childhood and continue to appear throughout life. AN are larger than common moles and measure 5-15 mm in diameter. The borders are irregular and ill defined. Macular and papular areas are often present. The color varies from tan to dark brown to pink to white.
Clinically they represent a transitional lesion in the spectrum between common melanocytic nevi and melanoma. Their biologic potential and histologic criteria are still not perfectly understood.
AN present a diagnostic dilemma. Common acquired nevi have a uniform pigmentation pattern. AN lack pigment uniformity and are difficult to differentiate from melanoma even with dermoscopy. The pigmentation pattern changes over time. This makes differentiation from melanoma by history very difficult. Ultraviolet light may initiate AN and then promote the transformation of melanocytes into atypical melanocytes or melanoma.