Methotrexate‐Associated Lymphoproliferative Disorders Characterized by a T‐Cell Phenotype With Lung and Psoas Involvement: A Case Report

Methotrexate (MTX) can cause MTX-associated lymphoproliferative disorders (MTX-LPDs) characterized by a T-cell phenotype. Herein, we report an extremely rare case of MTX-LPD with peripheral T-cell lymphoma (PTCL) phenotype and lung and skeletal muscle involvement. A 66-year-old man who had received MTX for 8 years for rheumatoid arthritis was admitted for right groin pain. A computed tomography scan revealed masses in the right middle lobe and right psoas muscle and multiple nodules in both lung fields. Pathological and immunohistochemical examinations of a lung nodule and psoas muscle tumor revealed PTCL. Remission was achieved soon after discontinuing MTX.