EP481 - An Unusual case of Fistulizing Large B-Cell Lymphoma Complicated by Post-Colonoscopy Perforation

Purpose/Background: Primary ileocolonic lymphoma is extremely rare, representing only 0.2-0.6% of all colorectal malignancies. They usually present as fungating or ulcerating or infiltrative lesion. We present a rare case of large B cell lymphoma presenting with entero-colic fistula in an immunocompetent patient and subsequent perforation after colonoscopy.

Methods/Interventions: The patient is a 91-year-old male with history of diabetes, coronary artery disease, hypertension admitted with abdominal pain, generalized body aches, joint pain and rigors. He had no known prior colonoscopy and family history was positive for glioblastoma in his son. CT scan of the abdomen and pelvis showed wall thickening or circumferential mass in the terminal ileum with surrounding fat stranding (Fig 1(a)). Colonoscopy revealed a large, circumferential, ulcerated lesion in the terminal ileum, fistulizing to the cecum, with the ileocecal valve opening appearing distinct and separate from the fistula (Fig 2 (a) and (b)). Biopsy was obtained and patient was discharged the next day. He represented to the emergency department the following day with severe abdominal pain, nausea and vomiting and physical exam showing peritonitis. CT showed focal enlargement of the terminal ileum with thickened walls and surrounding edema, consistent with prior findings, along with adjacent fluid, and gas, indicating perforation (Fig 1(b)). He underwent emergent open ascending colectomy and primary anastomosis. The postoperative course was complicated by ileus, which was managed conservatively, and the patient was eventually discharged on day 7.

Results/Outcomes: Pathology showed large B cell lymphoma, germinal center type, involving terminal ileum and cecum, with negative lymph nodes. The proliferative rate by Ki67 is 70%. A PET-CT will be obtained in a few weeks to allow for resolution of postoperative inflammation, ensuring more accurate staging. Given advanced age, patient is not a candidate for intense chemotherapy regimen, instead considering R-mini-CHOP.

Conclusion/Discussion: Malignant entero-colic fistula secondary to lymphoma is a rare complication, especially in patients who are immunocompetent. Patients typically present with vague nonspecific symptoms such as abdominal pain, diarrhea, and weight loss, and diagnosis is often delayed. Imaging modalities such as CT and endoscopic evaluation play a key role in diagnosis. Systemic chemotherapy (R-CHOP) is generally effective for both disease control and fistula resolution. However, surgery should be considered in the setting of complications such as perforation, obstruction, high-output fistula, or significant nutritional compromise.

Figure 1 (a) CT scan showing circumferential mass or wall thickening of the terminal ileum and (b) showing similar findings along with adjacent fat stranding, fluid, and free air indicating perforation
Figure 2 (a) colonoscopy picture showing appendiceal orifice (red arrow) and adjacent fistula to terminal ileum (yellow arrow) and (b) arrows pointing ileocecal valve and adjacent fistula