Air bronchogram: A potential indicator of epidermal growth factor receptor mutation in pulmonary subsolid nodules

Evaluation of pulmonary subsolid nodule is a longstanding clinical problem. We aimed to validate the computed tomography (CT) features correlating with pathological invasiveness and to explore any imaging findings associated with epidermal growth factor receptor (EGFR) mutation in lung adenocarcinoma.

A total of 204 patients with pathologically proven stage IA adenocarcinoma who had preoperative CT and data on EGFR status were enrolled in this retrospective study. Quantitative CT features including tumor size and solid volume proportion (SVP) were measured on multiplanar reconstructed images. Pathological analysis was stratified into adenocarcinoma in situ and minimally invasive adenocarcinoma (AIS/MIA), and invasive adenocarcinomas (IAs).

There were 93 AIS/MIA and 111 IAs. EGFR mutation was detected in 109 (53.4%) cases. In radiopathological analysis, IAs were significantly in larger tumor size (15.8mm vs. 10.9mm), higher SVP (18.3% vs. 1.1%) and more likely to present air bronchogram, vascular invasion, lobulated/irregular shape, non-smooth margin and pleural tag than AIS/MIA. The multivariate logistic regression indicated that tumor size (OR=1.337) and SVP (OR=1.198) were significant differentiating factors of IAs from AIS/MIA. In radiogenomic analysis, EGFR status differed in tumor size, air bronchogram and margin. The multivariate logistic regression disclosed that the presence of an air bronchogram (OR=3.451) was significantly associated with EGFR mutation after adjustment for age, gender and smoking status.

In subsolid nodules, tumor size and SVP were significant predictors of pathological invasiveness. In addition, the presence of air bronchogram was suggestive of activated EGFR mutation.