Analysis of the internal structure of peripheral pulmonary lesions using endobronchial ultrasonography

Study objective: To correlate the internal structure of peripheral pulmonary lesions, as visualized by endobronchial ultrasonography (EBUS), and the histology of the surgical specimen to develop a classification system for distinguishing benign from malignant lesions by EBUS. Design: Retrospective review. Setting: A national hospital. Patients: One hundred twenty-four patients with peripheral pulmonary lesions who had undergone EBUS in whom a definitive histologic diagnosis was made. In 69 patients, EBUS findings were correlated with the histology of a surgical specimen. Intervention: EBUS was performed by a miniature probe (20-MHz) introduced up to the lesion through a channel in a bronchoscope. Results: Three classes and six subclasses of lesions were identified by EBUS based on the internal structure of the lesion, focusing on internal echoes, vascular and bronchial patency, and the morphology of the hyperechoic areas, reflecting air in the alveoli and bronchioles. The classes of lesions are as follows: type I, homogeneous pattern (type Ia, with patent vessels and patent bronchioles; type Ib, without vessels and bronchioles); type II, hyperechoic dots and linear arcs pattern (type IIa, without vessels; type IIb, with patent vessels); and type III, heterogeneous pattern (type IIIa, with hyperechoic dots and short lines; type IIIb, without hyperechoic dots and short lines). Twenty-three of 25 type I lesions (92.0%) were benign, while 98 of 99 type II and III lesions (99.0%) were malignant. Twenty-one of 24 type II lesions (87.5%) were well-differentiated adenocarcinomas, and all type IIIb lesions were malignant, including 1.8 poorly differentiated adenocarcinomas (81.8%). Conclusions: EBUS permits the visualization of the internal structure of peripheral pulmonary lesions, and this information suggests the histology of the lesion.