MELANOCYTIC NEVI WITH FOCAL ATYPICAL EPITHELIOID CELL COMPONENTS - A REVIEW OF 73 CASES

Background: We report a variant of melanocytic nevus that may be confu sed with melanoma. Objective: The purpose of this study is to describe the clinical, histologic, and biologic features of nevi with focal at ypical epithelioid cell components (clonal nevi). Methods: Seventy-thr ee cases were retrieved by reviewing lesions previously diagnosed as c lonal, combined, deep penetrating, and inverted type-A nevi. Histologi c features were assessed and referring physicians received a questionn aire about the presentation and outcome of each case. Results: Histolo gically, all cases had a biphasic pattern characterized by an ordinary nevus that contained a darkly pigmented collection of large distinct epithelioid melanocytes in the superficial dermis. Immunostains identi fied mutant p53 proteins in 50% of dermal clones (9 of 18) but not in ordinary nevus cells adjacent to the clones. We are not aware of any p atient developing a malignant melanoma (mean follow-up 24.5 months), i ncluding 41 cases that were initially incompletely excised. Conclusion : Clonal nevi are a distinct variant of melanocytic nevi and should be distinguished from malignant melanoma arising in a preexisting nevus.