[Epidermal infiltration of melanoma]

The infiltration of the epidermis by malignant melanocytes is a characteristic phenomenon of cutaneous melanoma. A series of consecutive unselected cutaneous melanomas was histologically reviewed in order to study the frequency and the characters of epidermal infiltration. Such a feature was found in 86% of tumors (93% in superficial spreading melanomas); it was extensive in 65% of cases, focal in 35%; topographically, it was central and peripheral in 67%, peripheral in 30%, central in 3%. Results show that epidermal infiltration, albeit inconstant, is a useful feature in the histological diagnosis of melanoma (especially in SSM), provided that it is distinguished from pseudoinfiltration, a histologically similar, but intrinsecally different, feature observed in some benign melanocytic lesions.