NEUROENDOCRINE CARCINOMA OF THE SKIN WITH LYMPHOEPITHELIOMA-LIKE FEATURES

We report a case of primary neuroendocrine carcinoma of the skin (PNEC S) mimicking a lymphoepithelioma-like carcinoma of the skin (LELCS) wi th respect to both cytomorphology and the presence of a dense lymphopl asmacytic stroma. The tumor occurred in the left forearm of a 86-year- old woman, and its history was marked by aggressive behavior, with met astases to lymph nodes and to visceral sites within 1.5 years of diagn osis. The neoplastic epithelial cells had an immunophenotypic profile typical of PNECS, reacting for cytokeratin 20 and other low-molecular weight cytokeratins, neuron-specific enolase, neurofilament protein, s ynaptophysin, and chromogranin A. In addition, they were immunoreactiv e for epithelial membrane antigen, carcinoembryonic antigen, and S-100 protein, as observed in LELCS of supposed adnexal differentiation. Th e tumor-infiltrating lymphocytes were mostly of T-lineage, with a pred ominance of CD8+ cells. We believe the case is a morphologic variant o f PNECS, retaining its aggressive behavior and high metastatic potenti al, and should not be confused with true LELCS, which has a more favor able outcome. Immunohistochemistry is paramount in establishing the di agnosis. Lymphoid infiltration, even if prominent, does not seem to be of favorable prognostic significance in such a context.