Methotrexate‐associated lymphoproliferative disorders with angioimmunoblastic T‐cell lymphoma‐like features accompanied by gamma‐heavy chain disease in a patient with rheumatoid arthritis

: Although gamma heavy chain disease (γ-HCD) lesions occasionally morphologically resemble angioimmunoblastic T-cell lymphoma (AITL), no association has been described in detail due to the rarity of the disease. In this report, we present a rare manifestation of methotrexate (MTX)-associated lymphoproliferative disorders (LPDs) with AITL-like features accompanied by γ-HCD in a 75-year-old man with rheumatoid arthritis (RA). A biopsy specimen was evaluated using immunohistochemistry, clonal analyses of immunoglobulin VH and T-cell receptor γ gene rearrangements by polymerase chain reaction, and Sanger sequencing for confirmation of the structure of deleted γ-HCD clones. The histological features characterized by proliferation of CD4- and PD-1-positive medium-sized T cells and arborizing high endothelial venules together with numbers of small lymphocytes, eosinophils, plasma cells, and histiocytes in the background mimicked those of AITL, but did not completely fulfill the diagnostic criteria. Clonal analysis demonstrated that the specimen contained multiple LPDs of both B-cell and T-cell lineages. Sequence analysis confirmed the co-existence of a clone responsible for production of the abnormal heavy chain. This report provides new insights into the pathology of γ-HCD. Multiple host-derived factors (e.g., RA and/or use of MTX) may be responsible for the occurrence of LPDs of multiple lineages within a single lymph node.