Biopsy findings in PET/CT-positive lung lesions in a community hospital

An investigation was undertaken to determine the significance of fluorodeoxyglucose (FDG) uptake in lung abnormalities on positron emission tomography / computed tomography (PET/CT) in our practice. Factors such as lesion size, standard uptake value (SUV), multiplicity of pulmonary parenchymal abnormalities, and the presence of FDG uptake in mediastinal and hilar lymph nodes were analyzed as possible predictors of benign or malignant etiology.

PET/CT reports from 5/20/02 to 6/1/03 were reviewed, and 263 patients with significant FDG uptake (maximum SUV > or = 2.5) in pulmonary abnormalities were identified. This list of patients was cross referenced with pathology reports. Seventy-three of the 263 patients had biopsy results available for the corresponding PET/CT abnormality. These patients composed the study population. These PET/CT images, reports, and pathology reports were reviewed to determine the maximum SUV and size of the pulmonary lesion; the presence of additional pulmonary abnormalities and the presence of FDG uptake in mediastinal and hilar lymph nodes were recorded.

Eighteen of 73 patients had benign diagnoses at biopsy (25%), and 55 of 73 patients had pulmonary malignancies (75%). Size of the lesion and SUV were not useful in differentiating the benign from malignant groups. Multiplicity suggested a benign etiology, but was not statistically significant (p = .065). The presence of FDG uptake in mediastinal or hilar lymph nodes was a significant predictor of a malignant etiology for the pulmonary lesion (p = .024).

FDG uptake (SUV max > or = 2.5) in a pulmonary abnormality indicated a malignant etiology in 75% of patients. The presence of FDG uptake in mediastinal or hilar lymph nodes increases the likelihood to 81% that a "hot" pulmonary nodule or mass is malignant.