Further evaluation of a solitary pulmonary nodule (SPN) incidentally detected on chest radiography is not needed when either of the following two criteria (moderate evidence) is met: Nodule is stable in size for at least 2 years when compared to prior chest radiographs; there is a benign pattern of calcification demonstrated on chest radiography. Further evaluation of a pulmonary nodule showing a benign pattern of calcification, fat, or stability for 2 years or more on thin-section computed tomography (CT) is not needed (moderate evidence). In the absence of benign calcification, fat, or documented radiographic stability for at least 2 years, the choice of subsequent imaging strategy to differentiate between benign and malignant nodules is critically dependent on the pretest probability of malignancy. CT should be the initial test for most patients with radiographically indeterminate pulmonary nodules (moderate evidence). 18-Fluorodeoxyglucose positron emission tomography (18FDG-PET) has a high sensitivity and specificity for malignancy (strong evidence), and is most cost-effective when used selectively in patients where the CT findings and pretest probability of malignancy are discordant. The use of multidetector CT (MDCT) scanners with improved spatial resolution for lung cancer screening has led to the increased detection of small (<1 cm) pulmonary nodules. Nodules are categorized on CT as (1) solid, (2) part-solid (mixed solid and ground-glass attenuation), or (3) nonsolid (pure ground-glass attenuation). The imaging strategy for the further evaluation of small solid pulmonary nodules in the absence of a known primary malignancy is based on nodule diameter (moderate evidence). For solid nodules 4–10 mm in diameter, a strategy of careful observation with serial thin-section CT scanning is recommended at 6, 12, and 24 months. In patients with a known primary neoplasm, initial reevaluation at 3 months is recommended. For solid nodules larger than 10 mm in diameter, further evaluation with 18FDG-PET, percutaneous needle biopsy, or video-assisted thoracoscopic surgery (VATS) is recommended. Part-solid nodules (solid and ground-glass components) and nonsolid nodules (pure ground glass) detected at lung cancer screening have a higher likelihood of malignancy than solid nodules; therefore, tissue sampling (percutaneous CT-guided biopsy or VATS) is recommended (moderate evidence). For nodules less than 1 cm where this may not be possible, close serial CT evaluation at 3-month intervals in recommended.
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