Methotrexate-associated lymphoproliferative disease detected as a colorectal mass lesions: a case report.

Methotrexate-related lymphoproliferative disorder (MTX-LPD) is a rare but serious complication that occurs in patients treated with methotrexate (MTX); although MTX-LPD has been reported recently, the incidence in the colon is very low. A 79-year-old woman who had been receiving MTX for 15 years came to our hospital complaining of postprandial abdominal pain and nausea. Computed tomography scan showed the dilation of the small bowel and a tumor in the cecum. In addition, numerous nodular lesions were seen in the peritoneum. Ileal-transverse colon bypass surgery was performed for small bowel obstruction. Histopathological findings of both the cecum and the peritoneal nodules revealed the diagnosis of MTX-LPD. We report MTX-LPD occurring in the colon; it is important to consider MTX-LPD when intestinal symptoms occur during MTX therapy.