What is the probability that a lung nodule is benign?

Lung nodules are a common manifestation of lung disease. When lung nodules appear, you should be alert to lung cancer. Medical investigations have found that when lung nodules appear, the incidence of lung cancer is about 40%. Of course, there are many other factors. Lung nodules are diverse, and the location, size and shape of the nodules are different. If the growth is more obvious, the chance of cancer will increase exponentially.

What are lung nodules? Pulmonary nodules are small focal, rounded shadows with increased density on imaging. They may be solitary or multiple and are not accompanied by atelectasis, hilar enlargement, or pleural effusion. Solitary pulmonary nodules have no typical symptoms and are usually single, well-defined, increased density, ≤3 cm in diameter, and surrounded by air-filled lung tissue. In layman's terms, there are small white spots in the black lungs on the CT scan. A lung mass is considered to have a diameter greater than 3 cm, and is more likely to be lung cancer. In a recent study of chest CT scans obtained in adults from 2006 to 2012, more than 4.8 million people underwent at least one chest CT scan, more than 1.5 million nodules were found, and nearly 63,000 patients were diagnosed with new lung cancer within 2 years. Therefore, the importance of taking a systematic and evidence-based approach to the management of these nodules is obvious. The chance that a lung nodule may be lung cancer is about 40%, but it still depends on many factors.

Nodule diversity An analysis of multiple nodules in the NELSON study showed that when the nodule count was 1 to 4, the risk of primary lung cancer increased, but when the nodule count was 5 or more, the risk of primary lung cancer decreased, most of which were caused by the original granulomatous infection. It is generally believed that >10 diffuse nodules are likely to be accompanied by symptoms and may be caused by metastasis of extrathoracic malignant tumors or active infection, and the possibility of primary lung cancer is relatively small. Nodule location: Lung cancer occurs more often in the upper lobes, especially in the right lung. Nodule size and morphology For many years, spiculation of the margins has been considered an indication of malignancy, and recent studies have also confirmed spiculation as a risk factor for cancer. Unfortunately, spur signs are generally defined in a binary manner, that is, present or absent, and the critical value that determines whether a spur is present has not yet been determined. However, spiculation has been considered a risk factor for malignancy with an odds ratio of 2.2 to 2.5. Nodule growth: The volume doubling time of solid lung cancer nodules has been clearly defined (a doubling of volume is equivalent to a 26% increase in diameter), and the majority of nodules have a doubling time between 100 and 400 days. Subsolid lung cancer nodules, which are equivalent to primary adenocarcinomas, grow more slowly and are very common, with an average doubling time of approximately 3 to 5 years. Therefore, the Fleischner guidelines recommend that the first follow-up interval for subsolid nodules be delayed compared to solid nodules, and the total follow-up time be extended compared to solid nodules.

The relationship between age, sex, and smoking age and lung cancer risk is well established, with the risk of lung cancer increasing with age. Lung cancer is relatively rare in people under 35 and is uncommon before age 40. The incidence of lung cancer increases steadily with every 10-year increase in life expectancy. The possible role of gender in lung cancer risk factors has also been explored in several recent studies. Chiles et al. found in the NLST project that some individual characteristics of female subjects were associated with an increased risk of lung cancer, such as lower education level and lower body mass index; however, there was no significant difference in the overall cancer risk over 6 years compared with male subjects. Boiselle et al. in the same study explored the relative risks of women and men with solid, nonsolid, or part-solid nodules and found that women with ground-glass (nonsolid) nodules had a significantly higher risk. Smoking has been identified as a major risk factor for lung cancer. Although some patients have successfully avoided all the possible risk factors mentioned above, it does not mean that the possibility of lung cancer is zero, so lung nodules should be followed up. The following are the 2017 Fleischner guidelines recommendations for follow-up of incidental pulmonary nodules.

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