Assessment of usefulness of endobronchial ultrasonography in determinationof depth of tracheobronchial tumor invasion

Study objective: We assessed the usefulness of endobronchial ultrasonograph y in the determination of the depth of tumor invasion of the tracheobronchi al wall. Methods: We performed a needle-puncture experiment on normal tissue of 45 s pecimens to determine the laminar structure of the tracheobronchial wall. I n addition, we compared the ultrasonographic determinations of tumor invasi on from 24 lung cancer cases with the histopathologic findings. Results: The cartilaginous portions of the extrapulmonary bronchi and the i ntrapulmonary bronchi exhibited a five-layer structure. Starting on the lum inal side, the first layer (hyperechoic) was a marginal echo, the second la yer (hypoechoic) was the submucosal tissue, the third layer (hyperechoic) w as the marginal echo on the inner side of the bronchial cartilage, the four th layer (hypoechoic) was bronchial cartilage, and th fifth layer (hyperech oic) was the marginal echo on the outer side of the cartilage. In the membr anous portions, the first layer (hypoechoic) was a marginal echo, the secon d layer (hypoechoic) was smooth muscle, and the third layer (hyperechoic) c orresponded to the adventita. Comparisons between the ultrasonograms and th e histopathologic findings in 24 lung cancer cases revealed that depth diag nosis was the same in 23 lesions (95.8%) and was different in 1 lesion (4.2 %). In the single case in which the findings were different, lymphocytic in filtration that protruded between the cartilage rings was mistakenly interp reted as tumor infiltration. Conclusions: This method allows visualization of the laminar structure of t he tracheobronchial wall, which is impossible with other diagnostic imaging methods.