Fine-needle aspiration cytologic diagnosis of Kikuchi's lymphadenitis. A report of 27 cases.

Kikuchi's lymphadenitis is a self-limiting condition typically affecting young patients. Surgical biopsy is unnecessary if a firm diagnosis can be rendered by fine-needle aspiration cytology (FNAC). The authors report the FNAC findings for 27 cases, including 24 female and 3 male patients aged 12 to 43 years. Histologic sections of FNAC cell blocks and excisional biopsy specimens were available in 26 and 9 cases, respectively, for confirmation of the diagnosis. In the smears, karyorrhectic and granular debris were mixed with two distinctive cell types: (1) phagocytic histiocytes with peripherally placed "crescentic" (sometimes elongated or twisted) nuclei and abundant cytoplasm containing phagocytosed karyorrhectic or eosinophilic granular debris, easily distinguishable from tangible-body macrophages, which possessed central round nuclei, and (2) medium-sized cells possessing eccentrically placed round nuclei, fairly condensed chromatin, and a moderate amount of amphophilic cytoplasm, consistent with plasmacytoid monocytes. Also present were nonphagocytic histiocytes with twisted nuclei and delicate chromatin and immunoblasts that sometimes showed atypical features such as irregular foldings of the nuclei. Neutrophils were sparse or absent. Review of the FNAC findings of 50 lymph nodes involved by various reactive processes, tuberculosis, and lymphoma for comparison showed that although tangible-body macrophages and debris were not uncommon, very few phagocytic histiocytes with crescentic nuclei were observed, in only 2 cases; plasmacytoid monocytes were observed in 4 cases. The constellation of features described above permits diagnosis of Kikuchi's lymphadenitis by FNAC. Because of morphologic similarities between lupus lymphadenitis and Kikuchi's lymphadenitis, however, serologic studies are warranted to exclude systemic lupus erythematosus.