EP815 - Primary Colonic Anaplastic Large Cell Lymphoma Mimicking Medically Refractory Crohn’s Colitis

Purpose/Background: Primary colorectal lymphoma represents an uncommon malignancy, accounting for under 0.5% of all colorectal cancers. The cecum is the most frequent site, likely reflecting its rich lymphoid content, while rectal involvement has been reported in approximately 8-35% of cases. The cause remains uncertain, though links have been described with immunosuppressive conditions such as inflammatory bowel disease (IBD), HIV infection, and post-transplant states. Because symptoms often mimic benign inflammatory processes, diagnosis is frequently delayed, and many patients are identified only during urgent or emergent operations for obstruction or bleeding. Among T-cell lymphomas, anaplastic large cell lymphoma (ALCL) involving the colon is exceptionally rare and can imitate severe IBD. We describe a case of ALK-negative T-cell ALCL initially presumed to be medically refractory Crohn's colitis.

Methods/Interventions: A 27-year-old woman presented with abdominal pain, diarrhea, and pronounced thickening of the right colon. Colonoscopy demonstrated ulceration and skip lesions consistent with Crohn's disease. Despite 6 weeks of high-dose corticosteroids and biologic therapy (adalimumab/biosimilar), her symptoms and inflammatory markers worsened. Cross-sectional imaging revealed progressive wall thickening, new hepatic nodules, and enlarging mesenteric lymphadenopathy. Owing to near-obstructive changes and hemorrhage, an exploratory laparotomy with extended right colectomy and end ileostomy was performed. Intraoperatively, a >20 cm vascular omental and mesenteric mass was excised. Frozen section revealed a high-grade malignancy, and final pathology confirmed Stage IV ALK-negative T-cell ALCL.

Results/Outcomes: The postoperative period was complicated by pancreatitis, hemodynamic instability, and malignant effusions. The patient subsequently received BV-CHP chemotherapy (brentuximab vedotin, cyclophosphamide, doxorubicin, prednisone), leading to partial radiologic response and regression of hepatic and nodal disease.

Conclusion/Discussion: Primary colonic ALCL should be suspected when presumed IBD fails to improve with corticosteroid or biologic therapy, or when rapid progression and lymphadenopathy occur. Early tissue diagnosis is critical because ALK-negative ALCL follows an aggressive course with an estimated five-year survival of roughly 50%. This case highlights the importance of reconsidering malignancy in refractory or atypical IBD presentations, particularly in immunosuppressed or rapidly deteriorating patients.

Intraoperative picture of omental mass
Omental mass in close proximity to the stomach
Preoperative CT scan
Omental and Mesenteric mass with adenopathy and thickening of ascending colon