Lupus lymphadenitis simulating Kikuchi's lymphadenitis in patients with systemic lupus erythematosus: a clinicopathological analysis of six cases and review of the literature.

Kikuchi's disease (KD) or Kikuchi's lymphadenitis (KL) is a self-limiting disease mostly affecting the cervical lymph nodes of young individuals. Whether the reported cases of KL associated with systemic lupus erythematosus (SLE) were genuine KL or lupus lymphadenitis (LL) simulating KL in SLE patients is not clear. We analyzed six cases of KD-like lymphadenitis occurring in SLE patients and 12 reported cases to clarify the relationship between KL and SLE. We found that not all cases occurred simultaneously with SLE. Eight cases occurred either before or after SLE. These cases might have true KL independent of SLE with the exception of two cases that occurred after SLE, but the patients still had lupus activity. The 10 cases that coexisted with SLE most likely had LL rather than KL. This was supported by the immunohistochemical finding of sparse cytotoxic T cells in those lymph nodes in contrast to abundant cytotoxic T cells usually seen in a typical KL. We conclude that KL is not related to SLE, and KD-like lymphadenitis coexisting with SLE should be regarded as LL. Pathologists should be aware of the possibility that LL can mimic KL in patients with SLE, especially necrotizing-type KL.