Reversible methotrexate-associated lymphoproliferative disorder resembling advanced gastric cancer in a patient with rheumatoid arthritis.

A 73-year-old woman with rheumatoid arthritis had been treated with weekly low-dose methotrexate (MTX) for 5 years. She suffered from epigastric discomfort. Endoscopic examination revealed a tumor resembling advanced gastric cancer. Biopsy specimens showed atypical lymphoid cell infiltration. Immunohistological studies showed that these cells were positive for CD30 and CD79a, but not for CD15 or CD20. In situ hybridization identified Epstein-Barr virus latency-associated RNA expression in these cells. Clonally rearranged immunoglobulin heavy chain JH gene was not detected by Southern blot analysis. She was diagnosed with Epstein-Barr virus-associated polymorphic lymphoproliferative disorder (LPD) due to immunodeficiency caused by MTX administration. Cessation of MTX therapy led to complete regression of the tumor. To our knowledge, this is the first case of spontaneous remission of MTX-associated gastric LPD after discontinuation of MTX therapy. Increased awareness is needed on the possible occurrence of LPD resembling gastric cancer in rheumatoid arthritis patients treated with MTX.