BACKGROUND AND OBJECTIVEAir bronchogram were visible in endobronchial ultrasound images of benign and malignant lesions. The aim of this study is to analyze the endobronchial ultrasound images of different characteristics of air bronchogram and clinical significance combined with pathologic section.

METHODSFrom June 1, 2005 to December 30, 2008, 92 patients were found pulmonary peripheral lesions by X-ray and CT examinations, and confirmed that lesions were located lower to the segmental bronchial orifice by flexible bronchoscopy examinations. These patients were examined by radial endobronchial ultrasound probe afterwards.

RESULTSSeventy-eight patients clarified with benign or malignant diagnosis of lesions were analyzed, among whom, 22 of 47 (46.8%) were of malignant lesion without air bronchogram, 22 patients in 25 of lesions without air bronchogram were confirmed malignant (88%), among whom, 66.7% (2/3), were of small cell lung cancer, 43.9% (18/41) were of non-small cell lung cancer, and 50% (5/10) were of poorly differentiated adenocarcinoma, no sign of air bronchogram was found in corresponding pathological sections. Among those patients with malignant lesion, 51.1% (24/47) were of irregular air bronchogram. For patients with malignant lesions, irregular air bronchogram was most commonly found in adenocarcinoma, 55.2% (16/29) of pathological sections showed signs of air bronchogram, similar sign was also found in 2 patients with moderately differentiated adenocarcinoma and 1 patient with poorly differentiated adenocarcinoma. The total percentage of patients without air bronchogram and with irregular air bronchogram was 97.9% (46/47), only one of them (with medium differentiated adenocarcinoma) showed regular air bronchogram (1.3%). 80.6% (25/31) patients with benign lesion showed regular sign of air bronchogram distributed in the shape of concentric circles, the percentage of patients without air bronchogram or with irregular air bronchogram was both 3.8% (3/31).

CONCLUSIONWhen there's no air bronchogram, or irregular air bronchogram sign found by endobronchial ultrasound examination, it is highly indicated that there is a malignant lesion, while there's regular sign of air bronchogram distributed in the shape of concentric circles, it is likely to be a benign lesion.