Collision lung cancer on F-18 FDG PET/CT.

We report a case of a primary collision lung cancer consisting of squamous cell carcinoma and adenocarcinoma. A 73-year-old man with an abnormality found on chest radiograph in the right lower lobe was examined by FDG PET/CT (F-18 fluorodeoxyglucose positron emission tomography/computed tomography). The tumor was composed of 2 different morphologic and FDG accumulation portions and a collision tumor was suspected. Histopathologically, this tumor was composed of squamous cell carcinoma and adenocarcinoma. Each element was clearly distinguished but touched. FDG PET/CT is a useful tool to diagnose collision tumor as it shows morphologic and metabolic differences between 2 distinct tumor components.