Castleman disease and mimickers: Clinicopathological findings of atypical lymphoproliferative disorders associated with autoimmune disease

Atypical lymphoproliferative disorders (LPDs) related with autoimmune disease (AID) show marked clinicopathological diversity, which are defined as three distinct clinicopathological subtypes such as those resembling Castleman disease (CD), atypical paracortical hyperplasia with lymphoid follicles (APHLF), and atypical lymphoplasmacytic and immunoblastic proliferation (ALPIB). We studied excisional biopsy specimens from 31 patients with atypical LPDs associated with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and Sjögren syndrome (SjS). The lesions in these 31 cases were classified into 6 (19.4%) cases resembling CD, 14 (45.2%) cases of APHLF, and 11 (35.5%) cases of ALPIB. Five cases (83.3%) resembling CD were in the active stage with systemic symptoms and multicentric lymphadenopathy. Thirteen cases (92.9%) of APHLF showed systemic symptoms, multicentric lymphadenopathy and abnormal laboratory findings. Histologic findings for cases resembling CD were rare in patients with RA and SjS. In AID patients, histologic findings for cases resembling CD or APHLF findings correlated with disease activity and multicentric lymphadenopathy. Six cases (54.5%) of ALPIB were in the active phase with systemic symptoms and multicentric lymphadenopathy. ALPIB tended to be unrelated to AID activity, especially in the majority of patients with no abnormal laboratory findings. Atypical LPDs associated with AID is a group of diseases that may be overdiagnosed and overtreated. The diagnosis of atypical LPDs associated with AID requires an understanding of the histological findings as well as a comprehensive assessment of the presence of systemic symptoms, the distribution of lymphadenopathy, and abnormal laboratory findings.