S3971 An Uncommon Culprit: DLBCL Presenting in the Colon

Introduction: Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma (NHL) in the U.S., arising from B, T, or NK lymphocytes. Extranodal involvement is common, especially in the gastrointestinal (GI) tract, with the stomach being the most frequently affected site. In contrast, primary colorectal DLBCL is rare, accounting for less than 1% of all primary colorectal malignancies. Case Description/Methods: A 64-year-old man with a history of HTN and b/l OA, presented for screening colonoscopy due to prior adenomatous polyps. He was asymptomatic. Colonoscopy showed a neoplastic-appearing 30 cm sigmoid mass; bx confirmed DLBCL. Computed tomography showed a mass at the sigmoid junction with small (<9 mm) paracolic, mesenteric, and para-aortic lymphadenopathy. Bone marrow bx was negative. He completed 4 cycles of CHOP chemotherapy, post-treatment positron emission tomography (PET) showed persistent but improved sigmoid hypermetabolism post radiation therapy. Repeat colonoscopy found segmental inflammation from 18–30 cm without lymphoma on biopsy. PET scan showed disease progression with a larger hypermetabolic mass at the sigmoid junction and new LL quadrant adenopathy. He was started on ICE chemotherapy for 2 cycles. His course was complicated by colonic obstruction due to radiation colitis, requiring a diverting colostomy and persistent obstruction due to mass effect led to failure to thrive and PEG tube placement. He was transitioned to home hospice and later passed away. Discussion: DLBCL is the most common subtype of non-Hodgkin lymphoma, accounting for 25%–30% of cases. NHL represents about 80% of all lymphomas and includes over 30 subtypes, with DLBCL and follicular lymphoma being the most prevalent. DLBCL typically presents as a rapidly enlarging mass in either nodal or extranodal sites. While nodal involvement is more common, originating in lymph nodes, spleen, or thymus, 30%–40% of DLBCL cases are extranodal. The GI tract is a frequent extranodal site, with the stomach involved in 65% of GI cases, the small intestine in 20%–35%, and the colon and rectum in only 5%–15%. Colonic DLBCL is rare and often asymptomatic, sometimes discovered incidentally during routine screening, as in our patient. Treatment is typically based on histologic subtype, stage, and comorbidities, with R-CHOP chemotherapy (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) being the standard first-line regimen. Management may also include surgery or radiation in selected cases.