Plasmacytoid monocytes (so-called plasmacytoid T-cells) in Kikuchi's lymphadenitis. An immunohistologic study.

Three cases of Kikuchi's lymphadenitis were studied immunohistochemically on paraffin-embedded material in order to compare the plasmacytoid monocyte aggregates occurring in this disorder with plasmacytoid monocyte clusters in nonspecific reactive lymphadenitis. One of the cases was also analyzed on frozen material. In Kikuchi's lymphadenitis, plasmacytoid monocytes expressed the CD38 and LN1 antigens in addition to their monocyte/macrophage antigens found in nonspecific reactive lymph nodes. These plasmacytoid monocyte aggregates contained large numbers of Mac387+ lysozyme+ macrophages, scattered HLADR+ dendritic cells, and high numbers of CD8+ T-lymphocytes. Collections of T-immunoblasts or areas of necrosis were observed within these aggregates. The authors speculate that the histologic feature of Kikuchi's lymphadenitis is the morphologic substrate of a T-cell-mediated cytotoxic immune reaction occurring in plasmacytoid monocyte aggregates and resulting in plasmacytoid monocyte damage and necrosis.