Metastatic colon cancer to the lung with no detectable primary tumor, mimicking advanced primary lung cancer on F-18 FDG PET/CT imaging.

An 83-year-old man was referred with a right lung mass on dynamic chest computed tomography (CT). F-18 fluoro-deoxy-glucose positron emission tomography (FDG PET)/CT showed intense FDG uptake in the right lung mass and bilateral hypermetabolic mediastinal lymph nodes. CT-guided biopsy of the right lung mass revealed metastatic adenocarcinoma from the colon, but a colon cancer lesion was not detected by dynamic abdominal CT and colonoscopy.