Objective To investigate the clinical features, CT imaging features of benign and malignant pulmonary nodules, as well as the indicators for diagnosing the infiltration degree of malignant ground-glass nodules (GGN).

Methods A total of 205 patients with pulmonary nodules who underwent thoracoscopic surgery were selected as research subjects. According to the postoperative pathological results, they were divided into benign nodule group and malignant nodule group. The clinical features and imaging features of the two groups were analyzed. Based on the postoperative pathological results (infiltration degree), the patients with malignant GGN were further divided into preinvasive lesion (PL) group, minimally invasive adenocarcinoma (MIA) group, and invasive adenocarcinoma (IAC) group. Quantitative and qualitative analyses were conducted to screen for independent influencing factors of malignant GGN infiltration degree and evaluate their diagnostic value.

Results There were significant differences in nodule location, nodule type, pleural indentation sign, and vascular clustering sign between the benign nodule group and the malignant nodule group (P < 0.05). Multivariate Logistic regression analysis showed that nodule type, pleural indentation sign, and vascular clustering sign were independent influencing factors of benign and malignant pulmonary nodules (P < 0.05). There were significant differences in age, vascular clustering sign, nodule length, average CT value, and nodule type between the PL group and the MIA group (P < 0.05); there were significant differences in nodule length, average CT value, solid component length, vascular clustering sign, and pleural indentation sign between the MIA group and the IAC group (P < 0.05). Multivariate Logistic regression analysis showed that nodule length and average CT value were independent influencing factors of malignant GGN infiltration degree (P < 0.05). The receiver operating characteristic curve analysis showed that the area under the curve (AUC) of nodule length and average CT value for differential diagnosis of PL and MIA were 0.805 and 0.857, respectively, with cutoff values of 7.2 mm and -612.3 HU, respectively. The AUC of their combined diagnosis was 0.923; the AUC of nodule length and average CT value for differential diagnosis of MIA and IAC were 0.860 and 0.703, respectively, with cutoff values of 16.2 mm and -338.1 HU, respectively. The AUC of their combined diagnosis was 0.893.

Conclusion For GGN, especially those with pleural indentation sign and vascular clustering sign, a high suspicion of malignant pulmonary nodules should be raised. The length and average CT value of pulmonary nodules have certain diagnostic value for the infiltration degree of malignant GGN, and their combined application has higher diagnostic value.