[Spontaneous regression of methotrexate-related diffuse large B-cell lymphoma following bladder lesion resection].

A 71-year-old woman who had been treated with methotrexate (MTX) and prednisolone for rheumatoid arthritis since 2010 presented with hematuria. Cystitis was diagnosed. Chest and abdominal CT images revealed a bladder tumor, with lung and bilateral adrenal metastases. Transurethral resection of the bladder tumor (TUR-BT) confirmed these findings in September 2014. Histological findings of the bladder included large atypical lymphoid cells indicating diffuse large B-cell lymphoma. After TUR-BT, CT imaging showed that the tumor had shrunk. Still, MTX was continued. She was diagnosed with MTX-related lymphoproliferative disorders in November 2014 and MTX was discontinued. Fluorodeoxyglucose-positron emission tomography on March 2015 showed a complete response.