[Step section preparation of transbronchial lung biopsy material in diffuse lung disease].

We retrospectively prepared step sections of the transbronchial lung biopsy (TBLB) materials which revealed nondiagnostic findings in their original sections in patients with diffuse lung disease, and evaluated the significance of the examination of step sections in the diagnosis of diffuse lung disease. Of 131 cases with nondiagnostic TBLB findings, the preparation of step sections resulted in specific findings in 6 cases (malignancy 3 cases, tuberculosis 1 case, cryptococcosis 1 case and viral infection 1 case), and histopathological changes consistent with the clinical diagnosis in 25 cases. The step section preparation was especially useful for the detection of epithelioid granuloma and tumor tissue in patients with sarcoidosis and carcinoma, respectively, while its contribution to the diagnosis of collagen-vascular disease, hypersensitivity pneumonitis, atypical pneumonia and pneumoconiosis was relatively small. The step section preparation was also useful for the detection of bronchiolitis obliterans. In addition, step sections uncovered clinically unnoticed infection (purulent exudate in the alveolar space) in 6 cases, 3 of whom actually developed pneumonia thereafter. Thus, the preparation of step sections was considered to be useful clinically in 37 cases (28.2%). The preparation of step sections is recommended before a further diagnostic procedure is chosen, when TBLB performed in patients with diffuse lung disease reveals nondiagnostic findings.