CD138: A Potential Novel Diagnostic Marker for Cellular Neurothekeoma

ABSTRACT Background We incidentally observed CD138 (syndecan‐1) expression in a cellular neurothekeoma (CNT) and sought to investigate whether this is a consistent finding in these tumors. Methods We evaluated a series of 20 skin biopsy specimens diagnosed as CNT for CD138 immunohistochemical staining in comparison to the more traditional CNT immunohistochemical stains, NKI/C3 and MITF. Control cases of xanthogranuloma (XG), dermal Spitz nevi, and epithelioid fibrous histiocytomas (EFH) were included based on similar histopathologic morphology. Results CD138 expression in a membranous and reticulated extracellular pattern was observed in 95% of CNT cases evaluated. NKI/C3 was expressed in 83% of CNT, and MITF in 72%. Of the control cases, 10% of XG, 10% of dermal Spitz nevi, and 17% of EFH expressed CD138. Conclusions Our data suggest that CD138 may be a useful adjunctive marker in the diagnosis of CNT, particularly when utilized in a panel with other established markers such as NKI/C3 and MITF.