D107-13 TB or Not TB: Redefining a Presumed Metastatic Cancer

Abstract Introduction Tuberculosis (TB) is a well-known “great mimicker” that can present with clinical and radiographic features indistinguishable from malignancy. Disseminated TB is uncommon in immunocompetent patients and can be easily misdiagnosed as metastatic cancer. Early recognition is critical to avoid unnecessary intervention and improve morbidity. We describe an elderly man with multi-organ TB initially presumed to have widespread metastatic cancer. Case Presentation A 77-year-old man presented with progressive weakness and 35lb weight loss. CT abdomen/pelvis showed a cecal/terminal ileal wall thickening. CT Chest revealed a 3.8 cm cavitary left-upper-lobe mass with numerous small bilateral pulmonary nodules. Brain MRI demonstrated multiple enhancing lesions with vasogenic edema. Initial differential favored metastatic colon carcinoma with pulmonary/brain spread versus synchronous lung carcinoma with brain metastasis. Colonoscopy identified an ulcerated, fungating cecal/ileal mass. Biopsies showed chronic, moderately active colitis with non-necrotizing granulomas; Ziehl-Neelson stain demonstrated numerous acid-fast bacilli (AFB) within granulomas; Grocott Methenamine Silver (GMS) was negative; no dysplasia/malignancy was identified. Navigational bronchoscopic sampling showed granulomatous inflammation with multinucleated giant cells; Zieh-Neelson and GMS stains were negative. BAL was positive for Mycobacterium tuberculosis complex. In the context of multisite disease, both colonic tissue and BAL established disseminated TB (gastrointestinal, pulmonary, and CNS; brain lesions interpreted radiographically as tuberculomas). The patient was started on standard RIPE therapy along with adjunctive dexamethasone. Discussion This is a rare, disseminated TB that convincingly mimicked metastatic malignancy across gastrointestinal, lung, and brain in an older, immunocompetent host in a TB-endemic setting. Three evidence-based points are emphasized. (1) Biopsy the highest-yield site: in suspected disseminated infection, tissue from the most accessible lesion can be decisive; here, AFB-positive ileocecal granulomas clinched the diagnosis despite non-diagnostic respiratory studies. For extrapulmonary TB, negative smear/culture/NAAT results are common and do not exclude TB. (2) Imaging mimicry: cavitary upper-lobe disease with tree-in-bud/centrilobular nodules reflects endobronchial spread and can be mistaken for metastatic nodules; multiple ring-enhancing intracranial lesions are classic for tuberculomas yet overlap with metastases. (3) Epidemiologic context and rarity: although TB remains a major global burden, disseminated involvement affecting gastrointestinal, pulmonary, and brain is uncommon and prone to oncologic misdiagnosis; maintaining TB in the differential and pursuing tissue confirmation can avert unwarranted oncologic interventions and expedite appropriate management. This abstract is funded by: None