Primary Colonic Diffuse Large B-Cell Lymphoma Mimicking Colorectal Carcinoma: A Case Series

Abstract

Introduction: Primary colonic diffuse large B-cell lymphoma (DLBCL) is an uncommon extranodal malignancy that frequently mimics colorectal adenocarcinoma because of its non-specific clinical presentation and overlapping radiological features. Consequently, preoperative diagnosis remains challenging, particularly in patients presenting with acute intestinal obstruction. Presentation of Case: We report two female patients with primary colonic DLBCL who presented with intestinal obstruction. The first patient, a 68-year-old woman, presented with symptoms of intestinal obstruction. Computed tomography (CT) demonstrated bowel-wall thickening involving the caecum, ascending colon and ileocaecal valve, causing small-bowel obstruction. She underwent an emergency right hemicolectomy, during which an ascending colonic tumour was identified. Histopathological examination (HPE) confirmed DLBCL arising from the ileocaecal junction, classified as the non-germinal centre B-cell (non-GCB) subtype by immunohistochemical analysis. The second patient was a 42-year-old woman who also presented with obstructive symptoms. CT revealed a caecal and terminal ileal mass infiltrating the sigmoid colon. She underwent right hemicolectomy with en bloc anterior resection for a locally advanced caecal tumour. HPE confirmed DLBCL, not otherwise specified (NOS), arising from the caecum. Immunohistochemical analysis classified the tumour as the germinal centre B-cell (GCB-like) subtype. Discussion: Primary colonic DLBCL is a rare malignancy that may clinically and radiologically mimic colorectal carcinoma, making preoperative diagnosis challenging. Although systemic chemoimmunotherapy remains the cornerstone of treatment, emergency surgical intervention is often required for patients presenting with complications such as intestinal obstruction or perforation. Definitive diagnosis relies on histopathological examination, whereas subsequent management should be guided by appropriate oncological therapy and molecular subtype classification. Conclusion: Primary colonic DLBCL should be considered in the differential diagnosis of an obstructing right-sided colonic mass, despite its rarity. Histopathological confirmation and immunohistochemical subclassification are crucial for accurate diagnosis, prognostic assessment and appropriate oncological management.