Immunohistochemical detection of Kikuchi's lymphadenitis.

OBJECTIVE: To evaluate significance of immunohistochemistry in Kikuchi's lymphadenitis (KFD). METHODS: Biopsy specimens were obtained from 42 KFD cases for microscopic examination after the sections were stained with haematoxylin and eosin, and the immunohistochemical features were analyzed by monoclonal antibodies (CD20, CD8, CD45RO, CD57, CD68) and polyclonal antibody (myeloperoxidase, MPO). RESULTS: Morphologically, the lymph node lesions comprised various histiocytes, plasmacytoid monocytes, immunoblasts, small lymphocytes and nuclear fragments. In all the cases, the histiocytes were invariably observed and most of them were positive for CD68 and MPO. Immunoblasts and plasmacytoid monocytes were easily observed in proliferative stage. Immunohistochemical examination revealed strong focal T-cell positivity for the antibodies but with scarce B cell (CD20) and NK cell (CD57) positivity in the lesion area, where few or virtually no neutrophils were seen. CONCLUSION: Immunohistochemical analysis can be crucial for the differential diagnosis of KFD.