Thymoma associated with rheumatoid arthritis in a patient taking methotrexate.

Recently many patients with rheumatoid arthritis (RA) have been effectively treated with methotrexate. Until now, there have been no treatment related neoplasms reported in patients with RA taking methotrexate. Furthermore, there have been no reports of thymoma associated with isolated RA. We describe a patient with classical RA who developed a thymoma while being treated with methotrexate.