The patient was a 51-year-old woman who had a living donor kidney transplant 10 years ago for polycystic kidney disease. She was receiving immunosuppression with tacrolimus and prednisone. She had a failing allograft since 2005 and was being evaluated for retransplantation. Her creatinine level ranged from 2.0 to 3.0 mg/dL (to convert to micromoles per liter, multiply by 88.4). She presented with acute left lower quadrant abdominal pain and fever for 2 days, with no diarrhea, nausea, or vomiting. A computed tomographic scan of the abdomen showed a 4 × 4–cm and a 2 × 2–cm nodal mass in the mesentery with an asymmetrically thick-walled, dilated loop of bowel near it (Figure 1). A computed tomographic guided needle biopsy of the mesenteric mass was done because posttransplant lymphoproliferative disorder was suspected, which could be treated by cessation of immunosuppression and perhaps chemotherapy. Based on the initial histopathologic report of posttransplant lymphoproliferative disorder, immunosuppression treatment was stopped. About 24 hours after the biopsy, she developed severe abdominal pain; a plain film of the abdomen showed free air. On exploratory laparotomy, a thick-walled, distended loop of jejunum with perforation of the wall of the intestine about 7 to 8 cm from the duodenojejunal junction was found. There were a few lymph nodes adjacent to this mass as well as in the root of the mesentery. About 18 cm of the jejunum was resected, and end-to-end anastomosis was performed. The patient had acute pancreatitis in the immediate postoperative period but otherwise recovered uneventfully from the surgical procedure. Immunohistochemical staining showed strong positivity for CD31 (Figure 2). Her kidney transplant function remained stable at follow-up after 7 months.