Necrotizing lymphadenitis (Kikuchi's lymphadenitis; Kikuchi-Fujimoto disease) is seen most commonly in Japan and other Asian countries, but it also occurs elsewhere, including the United States and Western Europe. Most patients are young women with a persistent, painless cervical lymphadenopathy of modest dimensions that may be accompanied by fever. Microscopically, the affected nodes show focal, well-circumscribed, paracortical necrotizing lesions. There are abundant karyorrhectic debris, scattered fibrin deposits, and collections of large mononuclear cells. Special studies have shown that the necrosis is the expression of cytotoxic lymphocyte-mediated apoptotic cell death. Plasma cells and neutrophils are very scanty, a feature of diagnostic importance. Instead, plasmacytoid monocytes are often numerous. When the latter cells grow in a diffuse fashion, the appearance may simulate that of malignant lymphoma. On occasion, a prominent secondary xanthomatous reaction is seen. Ultrastructurally, tubuloreticular structures and intracytoplasmic rodlets similar to those described in lupus erythematosus are often found.
The diagnosis can be made or at least suspected in material from fine needle aspiration because of the prominence of phagocytic histiocytes with peripherally placed ("crescentic") nuclei and medium‑sized cells with eccentrically placed nuclei consistent with plasmacytoid monocytes.
The evolution is generally benign and self-limited. However, cases have been described with recurrent lymphadenopathy or accompanied by skin lesions. Isolated fatal cases are also on record. The etiology is unknown; an early suggestion that Toxoplasma may be involved has not been substantiated. Epstein-Barr virus (EBV), human herpesvirus (HHV)-6, HHV-8, and other viruses have been implicated, but the evidence for their involvement is not conclusive. The most important differential diagnosis is with malignant lymphoma with secondary necrosis. Cases of necrotizing lymphadenitis have been seen following diffuse large B-cell lymphoma, and changes morphologically consistent with necrotizing lymphadenitis have been reported in cases of stroma-rich Castleman's disease and in cases of lupus erythematosus.