From the Guidelines
Approximately 70% to 97% of incidental pulmonary nodules are benign. This estimate is based on recent guidelines from the Fleischner Society and American College of Chest Physicians (ACCP) 1. The likelihood of a benign etiology increases in younger patients without risk factors for lung cancer, non-smokers, and when nodules have certain radiographic characteristics such as complete calcification, small size, smooth margins, and stability over time. Some key factors that influence the likelihood of benign etiology include:
- Nodule size: smaller nodules are more likely to be benign
- Nodule appearance: nodules with smooth margins, complete calcification, and stability over time are more likely to be benign
- Patient risk factors: patients without a history of smoking, advanced age, or prior malignancy are more likely to have benign nodules
- Patient age: incidental pulmonary nodules found in patients <35 years of age are rarely malignant and more likely to represent infection 1. Common causes of benign pulmonary nodules include granulomas from previous infections, hamartomas, and inflammatory conditions. Despite the high likelihood of benign etiology, appropriate follow-up according to established guidelines is still recommended for incidental pulmonary nodules to ensure that the small percentage of malignant nodules are not missed, with the specific follow-up protocol determined by nodule size, appearance, and patient risk factors 1.
From the Research
Incidental Pulmonary Nodules
- The majority of incidental pulmonary nodules are benign, with studies suggesting that at least 95% of all pulmonary nodules identified are benign 2, 3.
- The percentage of benign incidental pulmonary nodules is high, with most being granulomas or intrapulmonary lymph nodes 2.
- Smaller nodules are more likely to be benign, with the probability of malignancy being less than 1% for all nodules smaller than 6 mm and 1% to 2% for nodules 6 mm to 8 mm 2.
Size and Malignancy Risk
- The risk of malignancy increases with the size of the nodule, with larger solid components being associated with a higher risk of malignancy 2, 3.
- Nodules that are 6 mm to 8 mm can be followed with a repeat chest CT in 6 to 12 months, depending on the presence of patient risk factors and imaging characteristics associated with lung malignancy 2.
- Ground-glass pulmonary nodules have a probability of malignancy of 10% to 50% when they persist beyond 3 months and are larger than 10 mm in diameter 2.
Management and Diagnosis
- The treatment of an individual with a pulmonary nodule should be guided by the probability that the nodule is malignant, safety of testing, the likelihood that additional testing will be informative, and patient preferences 2, 3.
- Management options include surveillance imaging, positron emission tomography-CT imaging, nonsurgical biopsy with bronchoscopy or transthoracic needle biopsy, and surgical resection 2, 3.
- Current bronchoscopy and transthoracic needle biopsy methods yield a sensitivity of 70% to 90% for a diagnosis of lung cancer 2.