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A 72-year-old man was evaluated for a three week history of fatigue, poor appetite and a ten-pound weight loss. He had a history of Wegener's granulomatosis and end stage renal disease. He received a living related kidney transplant nine years prior without complication. Physical examination, basic laboratory evaluation including electrolytes, complete blood count, hepatic function panel, and immunosuppressant levels were unremarkable. A Computed Tomography (CT) scan revealed an abnormally thickened ascending colon with multiple adjacent soft tissue masses and peritoneal nodules suggestive of a malignant neoplasm. A 18F-fluorodeoxyglucose positron emission tomography (PET)/CT was then obtained which revealed a corresponding hypermetabolic mass in the ascending colon and hepatic flexure (max SUV 18.5) with satellite lesions and enlarged mesenteric lymph nodes suggestive of colon cancer (figure 1). Subsequently, a colonoscopy was performed revealing an ulcerated mass with partial luminal obstruction at the hepatic flexure extending to the ascending colon (figure 2). Pathology from the mass showed active colitis with crypt distortion and granulomatous inflammation; no neoplastic cells were identified. Given there was still high suspicion for colon cancer, the patient then underwent right hemicolectomy. Pathology from the resection specimen showed ulceration with necrotizing granulomatous inflammation (figure 3). Stains for Acid-fast bacilli were positive (figure 4) and culture subsequently confirmed Mycobacterium tuberculosis.The World Health Organization estimates that there are approximately 8.8 million new cases of tuberculosis (TB) occurring each year. Though the incidence of TB has declined in the developed world, imunocompromised patients continue to be at risk. In intestinal disease, local effects of the bacilli lead to lymphangitis, endarteritis and fibrosis which can cause mucosal ulceration and inflammatory masses. A high index of suspicion is required for prompt diagnosis. Colonic TB often presents as a segmental masslike lesions with ulceration or as mucosal nodules, polyps, or strictures. Colonoscopy is successful in diagnosing TB in 60-80% of cases. Multiple biopsies of suspicious lesions are required which should be sent for acid fast staining, histology, and culture.The role of FDG-PET has not been clearly studied in intestinal tuberculosis. In PET scanning, FDG uptake correlates with increased tissue metabolic activity, which is non-specific and may be present in both inflammatory conditions and malignant neoplasms. Some inflammatory processes, including granulomatous diseases such as TB, may result in false positives. In these patients, active inflammation leads to increased local concentrations of neutrophils, lymphocytes and macrophages. These active inflammatory cells lead to increased intracellular glycolysis resulting in high accumulation of FDG. Therefore, positive results in the PET should be interpreted with caution when differentiating between benign vs. malignant lesions and should be co...

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