Expression of epithelial markers in PEComa of sacral ligament: a potential diagnostic pitfall

Perivascular epithelioid cell neoplasm/tumor (PEComa) was a relatively uncommon lesion of mesenchymal origin characterized by perivascular epithelioid cells with distinctive histological and immunohistochemical features. The occurrence in the sacral ligament was exceptional rare. Cytokeratin and epithelial membrane antigen (EMA) were considered as commonly useful epithelial markers to distinguish epithelial from mesenchymal tumor, but the expression of cytokeratin and EMA had also been seen in some mesenchymal tumor. Here, we presented an unusual case of PEComa of sacral ligament positive for cytokeratin and EMA, which was misdiagnosed as carcinoma. Our case suggested that the epithelial markers (including cytokeratin and EMA) show an overlap with that of PEComa, which represented a diagnostic pitfall for confusing PEComa with carcinoma.