How does FDG PET aid in the differentiation of benign and malignant lung nodules?
Malignant pulmonary nodules generally have increased glucose metabolism with increased uptake, trapping, and accumulation of FDG, a radioisotopic glucose analogue that can be detected on PET imaging. However, active inflammatory granulomatous pulmonary nodules may also show increased uptake of FDG. Lack of FDG uptake in a pulmonary nodule measuring 10 mm or more suggests benignancy, although malignant nodules that are due to AIS, MIA, or bronchial carcinoid or that are less than 10 mm may have low or absent FDG uptake. Dual-time-point FDG PET with early and delayed imaging can characterize pulmonary nodules further because malignant nodules tend to accumulate radiotracer over time, and benign nodules tend to wash out radiotracer gradually. In general, FDG PET/CT is useful for characterizing lung nodules, and it is currently recommended when a solid indeterminate lung nodule >8-10 mm in diameter is present in the setting of a low-moderate pretest probability of malignancy or when a persistent part-solid indeterminate nodule >8–10 mm in diameter is present.
