Plasma cell infiltrate in common acquired melanocytic nevus

The presence of plasma cells in melanocytic lesions has been considered in literature as a sign of concern, when evaluated in the appropriate context. Plasma cells have been evaluated in halo nevus, but they are not frequently reported in non-halo common acquired nevus. Our claim was to study how common and frequent plasma cells are in the latter type of nevi. Therefore, we examined 280 of these nevi and selected the cases with an inflammatory infiltrate, even if mild. We then looked for plasma cells in the inflammatory infiltrate in the hematoxylin-eosin routine sections and selected 17 cases in which plasma cells (even if only occasional) could be found in the hematoxylin-eosin staining. Out of these 17, plasma cells were easily found in four cases, which were then further studied with immunohistochemistry for epithelial membrane antigen. The percentage of plasma cells varied in these four cases from 0.5% to 7%. No relation between the amount of plasma cells and either the location of the nevus or the location of the inflammatory infiltrate could be established. We conclude that the main point of this study is not to trust the presence of plasma cells as a solid criterion on its own, when evaluating a melanocytic lesion.