Imaging of lung hamartomas by multidetector computed tomography and positron emission tomography

Background. Hamartomas constitute 8% of solitary lung nodules and 75% of benign nodules. Most are discovered on routine x-ray film and require further evaluation. Computed tomography (CT) is insufficient for a benign versus malignant diagnosis in about 30% of cases. Methods. We retrospectively assessed the ability of CT with contrast and [F-18] fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) to diagnose nonmalignancy in 42 consecutive pathologically confirmed hamartomas, with the aim of reducing the number of invasive procedures in future cases. Computed tomography was assessed as probably benign or probably malignant based on one radiologist's subjective evaluation. The PET/CT images were assessed according to uptake relative to normal parenchyma and mediastinum. Results. Computed tomography was probably benign in 26 cases (62%) and probably malignant in 16 (38%). The PET/CT scan was benign in 34 cases (81% [standard uptake value available in 16: mean 1.1, SD 0.5]), suspicious in 4 (9.5%), and malignant in 4 (9.5%). The 34 nodules benign by PET/CT had mean size 14.3 mm (SD 7.8) compared with mean 22.7 mm (SD 10) in the 8 nodules malignant/suspicious by PET/CT. Of these 8 nodules, 6 were probably benign by CT and 2 were probably malignant; thus CT and PET/CT concurred on malignancy in only 2 cases. Conclusions. The present study is the first specifically concerned with the CT and PET/CT characteristics of a pathologically confirmed series of lung hamartomas. Our findings support the role of PET/CT in characterizing solitary lung nodules, although about 20% of (mainly large size) hamartomas had uptake characteristics suggesting malignancy.