Histiocytic necrotizing lymphadenitis (Kikuchi–Fujimoto disease): continuing diagnostic difficulties

AIMS: To describe the clinicopathological and immunophenotypic features of 25 cases of Kikuchi-Fujimoto disease (K-F), which remains a poorly recognized entity and is still frequently confused with malignant lymphoma, and to discuss the main diagnostic problems experienced by the referring pathologist. METHODS AND RESULTS: Haematoxylin and eosin sections of 27 lymph node biopsies were re-examined. Immunostains for B-lymphocytes, T-lymphocytes and macrophages were performed. Clinical and follow-up data were obtained through a questionnaire to the referring pathologist or from the patients' notes where available. The suggested initial diagnoses are discussed. The lymph nodes showed a necrotizing process characterized by patchy or confluent areas of necrosis associated with karyorrhexis and absence or paucity of granulocytes. This was associated with a proliferation of large blastic cells consisting of a mixture of T-lymphocytes and histiocytes. Fragmentation of the biopsy was a frequent feature. The diagnosis of K-F was suggested by the referring pathologist in three cases only. The most common suggested diagnosis was that of a non-Hodgkin's lymphoma. CONCLUSION: This series documents continuing difficulties in the diagnosis of Kikuchi-Fujimoto disease in the UK and emphasizes that cases are still being mistakenly diagnosed as malignant lymphomas. The diagnosis of Kikuchi-Fujimoto disease merits active consideration in any nodal biopsy showing fragmentation, necrosis and karyorrhexis, especially in young women presenting with cervical lymphadenopathy.