False Positive Result of Dual Phase 18F-FDG PET/CT Imaging in a Patient with Xanthogranulomatous Cholecystitis

Abstract

A 61-year-old man visited our hospital due to a history of right upper abdominal pain and abnormally elevated liver function test. An abdominal CT scan showed a tumor in the segment 4 of liver. Either gall bladder cancer with invasion to liver and peritoneum or hepatocellular carcinoma (HCC) was impressed. According to the imaging findings and elevated CA 19-9 level (43.7 U/mL), gallbladder cancer was considered first. Dual phase fluorine-18-fluorodeoxyglucose (18F-FDG) combined positron emission tomography (PET)/computed tomography (CT) imaging revealed abnormal metabolic activity in the lesion with a high maximal standardized uptake value of 11.2 in early scan and slightly increased to 11.7 in delayed scan. The result of PET/CT was compatible with gallbladder cancer. He received operation and was diagnosed by histopathological examination as having a xanthogranulomatous cholecystitis (XGC). XGC is a destructive inflammatory disease of the gallbladder, mimicking an advanced gallbladder carcinoma and rarely involving adjacent organs. The diagnosis is usually possible only after pathological examination. We reported a case of XCG with uncommon pattern of invading liver, omentum and transverse colon and caused false positive results on 18F-FDG PET/CT imaging. Therefore, 18F-FDG PET/CT results should be interpreted with caution in differentiating a benign inflammatory process from malignant abnormalities, especially in regions with a high probability of granulomatous lesion.