S2783 Ileocolonic Fistula Due to Diffuse Large B-Cell Lymphoma: Unusual Presentation of a Rare Disease

Abstract

INTRODUCTION: Malignant fistula is a rare complication of primary gastrointestinal lymphomas (PGIL) such as primary aggressive diffuse B cell lymphoma (DLBCL) of the ileum. These fistulas are frequently misdiagnosed. Currently there is no standardized treatment approach. We present a case of DLBCL complicated with a malignant ileocolonic fistula in a 55-year-old male with favorable outcome after surgery and chemotherapy. CASE DESCRIPTION/METHODS: A 55-year-old male presented with 3 months of watery non-bloody diarrhea and 3 weeks of abdominal pain associated with nausea. He denied any vomiting, anorexia, weight loss, fever or chills. Labs revealed a CRP of 15.3 mg/dl and leukocytosis of 14.3 k/ul. Non-contrast CT of abdomen and pelvis showed a focal aneurysmal dilation of a small bowel loop in the mid lower abdomen with associated lymphadenopathy and fluid filled sigmoid colon consistent with a small bowel tumor with an enterocolonic fistula (Image). This was confirmed on colonoscopy which showed a large sigmoid fistula 30 cm from the anal verge communicating with the midgut lumen through a medium sized ulcerated mass (image). He underwent en bloc excision. Both colonoscopy and surgical pathology confirmed high grade primary DLBCL, germinal center like originating from the ileum. Post-operative PET/CT scan showed persistent neoplastic process in the left para aortic lymph nodes. He received 6 cycles of R-COEP with complete resolution of symptoms. Follow up PET/CT scan showed no residual disease and was declared to be in complete remission. DISCUSSION: Ileocolonic fistulas due to PGIL is a rare occurrence with only less than 10 cases reports that we were able to find in literature. These fistulas are commonly misdiagnosed due to unspecific clinical presentation. Currently, there is no consensus on the standard treatment approach. We acknowledge the approach of en bloc surgical resection with adjuvant chemotherapy because of the excellent clinical outcomes observed with our patient, but admit that more data is required to demonstrate the most effective approach to treat PGIL.Figure 1.: Unenhanced cross section CT scan of the abdomen showing an ileocolonic fistula with aneurysmal dilation of the small bowel.Figure 2.: Endoscopic picture showing the fistula at 20cm from the anal verge(left) and a small bowel fistulizing mass(right).Figure 3.: H&E (left) and BCL6 (right) stained histology slides showing Malignant high grade DLBCL cells infiltrating the small bowel.