Table 1. Histologic Criteria for Diagnosing Melanoma1
Breadth usually >6 mm
Poor circumscription; atypical melanocytes beyond the most peripheral discrete nest of melanocytes within the epidermis
Increased number of single atypical melanocytes within the epidermis and epithelial structures of adnexa and, in some foci, single melanocytes predominate over nests of them
Melanocytes scattered in the upper reaches of the epidermis
Variation in the size and shape of nests of melanocytes
Nests of melanocytes are not equidistant
Irregular shapes of nests of melanocytes
Tendency of nests of melanocytes to confluence
Failure of maturation of atypical melanocytes, with progressive descent into the dermis
Asymmetrical, patchy distribution of melanin within the neoplasm
Extension of atypical melanocytes far down the epithelial structures of the adnexa
Asymmetrical distribution of inflammatory cell infiltrates of variable densities at the base of the neoplasm