Methotrexate-associated lymphoproliferative disorder demonstrating composite lymphoma of EBV-negative diffuse large B-cell lymphoma and EBV-positive mucocutaneous ulcer.

Other iatrogenic immunodeficiency-associated lymphoproliferative disorders induced by immunosuppressive drugs, such as methotrexate (MTX-LPD), exhibit numerous pathological findings. We report the case of an 81-year-old Japanese woman diagnosed with MTX-LPD exhibiting two distinct pathological features from two different sites. Excisional biopsy of the left cervical lymph node revealed EBV-negative diffuse large B-cell lymphoma and biopsy of a pharyngeal ulcer revealed EBV-positive mucocutaneous ulcer. She was treated using an R-CHOP regimen and maintained complete remission for years. This case demonstrates the heterogeneous pathology of MTX-LPD and suggests the necessity of multiple biopsy.