Melanoma in situ with epidermal effacement: a compelling adjunctive finding.

Since many studies have shown the discordant diagnoses of melanocytic lesions among pathologists despite the existence of an established histologic criteria, we sought to refine the histologic criteria by finding an additional reliable and reproducible objective histopathologic feature to aid in the diagnosis of melanoma in situ. We performed a retrospective analysis of 100 cases histologically diagnosed as melanoma in situ and compared them to a study control group consisting of junctional benign melanocytic nevi. The epidermis of all the melanocytic lesions was examined for epidermal effacement. Examination of the epidermis in the study group revealed an absence of epidermal effacement in only 7 (10%) cases, whereas 93 (93%) cases showed an absence of rete ridges in some foci, making this an overwhelming majority finding in the cases examined. These results serve as a compelling adjunctive finding that can be used to increase the histologic diagnostic accuracy of melanoma in situ.