Atypical large plasma cells in lymph node granulomas in cat-scratch disease.

A histological variant of plasma cells found in the granulomas of cat-scratch disease (CSD) lymphadenitis is reported. Though the lesion shows the typical features of suppurative granulomatous lymphadenitis, many atypical giant cells which have abundant basophilic cytoplasm and bizarre nuclei with occasional multinucleated forms are noted among epithelioid histiocytes. The diagnosis of CSD lymphadenitis was confirmed by comparing clinical; histopathological, and histochemical (Warthin-Starry silver impregnation stain) studies on lymph node sections from five cases with features typical of the disease. Histochemical (methyl green-pyronine stain) and immunohistochemical examination provided several lines of evidence indicating that the atypical giant cells in our case were plasmacytic and confirmed that its proliferation was reactive, not neoplastic. Multinucleated giant cells were also occasionally present in the other five cases, but they had histological and immunohistochemical features of Langhans' type giant cells. We stress the importance of distinguishing such atypical large plasma cells from neoplastic cells.