Mimicry in the Abdomen: When Colonic Lymphoma and Tuberculosis Collide: A Case Report

Background: Colonic lymphoma is a rare malignancy, accounting for less than 1% of all gastrointestinal neoplasms. Concurrent lymph node tuberculosis (TB) in the setting of colonic lymphoma is extremely uncommon and poses diagnostic and therapeutic challenges. Case Presentation: We report the case of a 30-year-old male with no significant medical history, referred for suspected acute appendicitis. The patient presented with recurrent episodes of right iliac fossa pain over five months, accompanied by alternating constipation and diarrhea. Physical examination revealed tenderness and a mass effect in the right iliac fossa. Abdominal ultrasound demonstrated a circumferential thickening of the ascending colon (32 mm) with necrotic lymphadenopathy and mild pelvic fluid collection. Contrast-enhanced CT confirmed a non-stenosing circumferential thickening (35 mm) of the ascending colon extending over 10 cm, with deep infra- and juxtacentimetric lymph nodes, some showing central necrosis. Colonoscopy revealed a passable, rigid, circumferential stenosis of the ascending colon. Histopathological and immunohistochemical analyses of colonic biopsies confirmed B-cell lymphoma. The patient underwent a right hemicolectomy, and histological examination of the deep lymph nodes revealed epithelioid granulomas with caseous necrosis, confirming tuberculous lymphadenopathy. The patient was treated with a combination of standard antituberculous therapy and chemotherapy under hematology-oncology supervision. Conclusion: This case highlights the diagnostic complexity of colonic lymphoma coexisting with lymph node TB. Advanced imaging, histopathology, and molecular studies are crucial for differentiating these entities and guiding appropriate management.