[Small intestinal perforation manifesting as post-transplant lymphoproliferative disorder occurring 23 years after living lung transplantation: a case report].

A Japanese female patient underwent a living lung transplant at age 29 and has been on immunomodulatory drug therapy since then. At age 52, she presented with sudden hematochezia. Despite abdominal computed tomography scan, esophagogastroduodenoscopy, and colonoscopy, no definitive source of bleeding was identified. Considering the possibility of small bowel bleeding, video capsule endoscopy was performed, which revealed a suspected ulcerative lesion in the jejunum. Subsequent per-oral double-balloon endoscopy confirmed the presence of an ulcerative lesion in the jejunum. A potential pathological diagnosis of post-transplant lymphoproliferative disorder (PTLD) was considered based on endoscopic biopsy specimens from the jejunal lesion. However, before the pathologic biopsy results were available, the patient experienced small intestinal perforation, necessitating emergency partial resection. Pathologic examination revealed a dense proliferation of medium-to-large atypical lymphocytes with neutrophilic infiltration in the perforated area of the small intestinal wall. Immunostaining showed lymphoid cells positive for CD20 but negative for CD3. Epstein-Barr virus (EBV) -encoded RNA was detected by in situ hybridization, and Ki-67 staining demonstrated a higher percentage of positive cells. Consequently, an EBV-positive diffuse large B-cell lymphoma, developed as PTLD, was diagnosed. Complete remission was achieved with a reduced immunomodulatory drug dosage and rituximab therapy. She has been alive for 8 months postoperatively without recurrence. This case suggests that PTLD should be considered in assessing patients presenting with abdominal symptoms following organ transplantation.