Clinicopathological and immunohistochemical analysis of oral melanocytic nevi and review of the literature.

INTRODUCTION: Oral melanocytic nevi (OMNs) are uncommon benign melanocytic tumors, histologically similar to their cutaneous counterparts. The aim of this study was twofold: to contribute to the epidemiology with a literature review with the first Spanish series of OMNs, and to report on clinicopathological, immunohistochemical and demographic findings.

MATERIALS AND METHODS: A retrospective analysis of cases attended over the period 1999-2010 was carried out using data drawn from the pathology unit files at two public hospitals in the Spanish region of Andalusia, serving between them a population of 823.614 inhabitants (11%).

RESULTS: Ten cases of OMNs were retrieved, accounting for 0.18% of the total 5499 oral biopsies performed over the period. The female-to-male ratio was 1.5:1; mean patient age was 30. The palate was the most common location (70%). Relative frequencies of histologic types were as follows: subepithelial (40%), common blue (30%), compound (20%) and junctional (10%). Immunohistochemical examination showed strong S-100 protein expression, variable reactivity to HMB-45 and high c-Kit expression by junctional melanocytes. Ki-67 was ≤3 in all cases.

CONCLUSIONS: Although this first clinicopathologic analysis of OMNs reported in Spain was based on a small patient series, the results are in line with those reported in larger series and additionally provide new demographic data. Since OMNs and early melanomas are usually detected at routine dental examination, detailed oral exploration should always be performed, and in case of doubt a biopsy should be taken to ensure an accurate diagnosis.