Late-Onset Post-Transplant Lymphoproliferative Disorder Presenting as Diffuse Large B-Cell Lymphoma in the Ascending and Transverse Colon: 1598

INTRODUCTION: A serious complication of solid organ transplantation is post-transplant lymphoproliferative disorder (PTLD). The vast majority of PTLD was previously found to present within the first year after transplant, when immunosuppression is highest. However, newer studies suggest a bimodal peak in incidence. 1 This case describes PTLD occurring in the colon as a late complication of multi-organ transplant. CASE DESCRIPTION/METHODS: A 54-year-old male with a complicated transplant history, on tacrolimus for immunosuppression, presented with worsening abdominal pain, nausea, diarrhea, and weight loss. His transplant history includes cardiac transplants in 1980 and 1993 for idiopathic cardiomyopathy, and renal transplant in 2003 due to tacrolimus toxicity. He denied fever, night sweats, or recent sick contacts, and was hemodynamically stable. On exam, he had diffuse abdominal pain with mild guarding but no rebound. Laboratory findings revealed a tacrolimus level of 11.1. Abdominal computed tomography scan was significant for fluid-filled loops of small bowel with focal thickening of the transverse colon, concerning for colonic malignancy (Figure 1). Gastroenterology was consulted for urgent colonoscopy, which showed mucosal ulceration and inflammation throughout the colon, with sparing of the sigmoid and rectum (Figure 2). Biopsy of the cecum, ascending colon, and transverse colon revealed diffuse infiltrate of pleomorphic large cells in the lamina propria and submucosa with focal ulcerations and necrosis, consistent with PTLD of monoclonal diffuse large-B cell morphology. The biopsy was negative for EBV and CMV. Immunohistochemistry was positive CD45RB, CD79a, CD30 and BCl2. He was referred to hematology-oncology and followed-up as an outpatient to begin chemotherapy. DISCUSSION: Though PTLD is classically described as an early complication of solid organ transplant, this case presents the development of colonic PTLD after over 15 years since last transplant. This finding supports the notion that there is a bimodal peak in incidence. This case also demonstrates the insidious, non-specific gastrointestinal findings of colonic PTLD. Because of this, and as survival after organ transplant continues to increase, providers must have a high index of suspicion for PTLD in the colon as a late complication of transplant.