Intestinal Tuberculosis Masquerading as Metastatic Colonic Malignancy: A Diagnostic Dilemma in an Elderly Patient

Abdominal tuberculosis (TB) and colorectal malignancy have overlapping clinical, endoscopic, and radiological features leading to difficulty in diagnosis. We describe a case of abdominal TB mimicking colon cancer, with the added dramatic complication of false-positive positron emission tomography (PET)-computed tomography (CT) findings. Our patient is a 76-year-old woman with type 2 diabetes mellitus, chronic kidney disease, and ischemic heart disease, describing a 2-month history of vomiting and loose stools, with symptoms of anorexia, weight loss, and progressive abdominal distension. Colonoscopy revealed circumferential ulceroproliferative growth at the transverse colon with luminal narrowing. On PET-CT scan, there were fluorodeoxyglucose-avid epiphrenic lymphadenopathy and peritoneal deposits suggesting metastatic colonic carcinoma. However, colonoscopic biopsy showed granulomatous ulcero-inflammatory change with multinucleated giant cells and positive acid-fast bacilli (AFB), but ruled out malignancy. GeneXpert MTB/RIF on sputum and ascitic fluid was negative. Ascitic fluid analysis revealed a low serum-ascites albumin gradient with high protein, consistent with tuberculous peritonitis. Antitubercular therapy (ATT) was initiated. At 8-week follow-up, the patient gained weight, and ascites had substantially regressed. This case highlights the critical importance of tissue biopsy with special staining in elderly patients from TB-endemic countries presenting with colonic lesions and PET-CT findings that mimic disseminated malignancy. AFB staining of colonoscopic biopsies should be a routine component of the diagnostic workup in such settings, and a negative GeneXpert should not exclude abdominal TB.