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Washington University Experience | NEOPLASMS (HEMATOLYMPHOID) | Rosai-Dorfman Disease | 9B4 Rosai-Dorfman Dz, dura (Case 9) H&E 1.jpg
Ancillary studies (slides no longer available): The large histiocytic cells are strongly immunoreactive for S-100 protein, the latter highlighting foci of emperipolesis. There is weaker immunoreactivity for CD68, which also highlights smaller histiocytic cells within the lesion. There are numerous CD3-positive T cells, CD20-positive B cells, and CD138-positive plasma cells. In situ hybridization for Kappa and Lambda show a mixed population of plasma cells, consistent with a polyclonal process. The tumor cells are negative for CD1a. ---- Comment: The morphologic and immunohistochemical features are consistent with the diagnosis of extranodal Rosai-Dorfman disease. (RDD)
