Association of methotrexate, rheumatoid arthritis and lymphoma: report of 2 cases and literature review.

We describe 2 Caucasian men with rheumatoid arthritis (RA) who developed non-Hodgkin's lymphoma of identical histological type during treatment with low dose oral weekly methotrexate (MTX). Both patients had longstanding RA and had been treated with MTX for over 2 years at time of tumor diagnosis; neither had secondary Sjögren's syndrome. The oncogenic potential of MTX and RA arthritis is reviewed.