Morphological analysis of nevoid melanoma - A study of 20 cases with a review of the literature

Nevoid melanoma is a rare variant of melanoma characterized by deceptive mo rphologic features reminiscent of a benign melanocytic nevus. Twenty (13 no dular, 7 verrucous) nevoid melanomas were reviewed with the goal of identif ying the predominant architectural patterns, cytologic features, and progno stic indicators. Although at scanning magnification, many lesions showed a strong resemblance to banal compound or dermal nevi, careful inspection in all cases demonstrated subtle pleomorphism and impaired maturation with dep th, invariably accompanied by multiple dermal mitoses. Four tumors recurred and three metastasized, with subsequent death of the patients. Follow-up i nformation for a period of at least 3 years was available in eight cases. I n this group, mortality was 37.5%, the metastasis rate was 37.5%, and the l ocal recurrence rate was 75%, with an average tumor thickness of 2.5 mm. We conclude that nevoid melanoma may be distinguished from a benign melanocyt ic nevus by a high index of suspicion, a careful analysis of architecture, and attention to cytologic features. Our data and a review of the literatur e do not support the notion that nevoid melanoma has a better prognosis tha n ordinary melanoma.