[2-year complete remission after withdrawal of methotrexate in a rectal methotrexate-associated diffuse large B-cell lymphoma].

A 71-year-old man, who had been receiving methotrexate (MTX) and prednisolone for the treatment of rheumatoid arthritis, was admitted to our hospital in August of 2004 with rectal hemorrhage. Histological examination of an ulcerative lesion of the rectum revealed diffuse large B-cell lymphoma (DLBCL). Chemotherapy with the CHOP regimen with dose reduction following cessation of MTX was initiated. However, the patient experienced septic shock secondary to febrile neutropenia and was then followed up without chemotherapy. The DLBCL rectal lesion regressed spontaneously thereafter and had resolved completely without treatment 2 years after the initial presentation, suggesting that the withdrawal of MTX led to regression of the DLBCL. The DLBCL in our patient is compatible with MTX-associated lymphoproliferative disorders. Immunoglobulin gene rearrangement and Epstein-Barr virus (EBV) infection found in tumor cells indicated that the EBV was involved in the monoclonal proliferation of B-cells in this patient whose immune function was suppressed by MTX therapy.