Transbronchial and endobronchial biopsies are procedures of limited invasiveness performed by bronchoscopy, typically aided by fluoroscopy, with less morbidity and mortality than wedge lung biopsy, which is performed by thoracoscopy or by open surgery; however, they provide a limited amount of tissue from a restricted sampling area. Specimens typically are no more than 2 to 3 mm in size. Endobronchial biopsies may contain bronchial epithelium and underlying bronchial wall, including subepithelial tissue, bronchial glands, muscle, and cartilage. Peribronchial lymphatic and vascular structures may also be present. Successful transbronchial biopsies also include lung parenchyma.

The decision to attempt a transbronchial biopsy as opposed to a thoracoscopic or open wedge biopsy is based on (1) whether histopathologic diagnosis of the suspected disease is possible by small sample, (2) the probability of sampling diagnostic tissue by transbronchial biopsy, and (3) the risk/benefit ratio for the patient. Therefore, diagnosis by endobronchial or transbronchial biopsy depends on the type of disease and the distribution of the disease. Neoplasms, infections, and some interstitial lung diseases are diagnosable by endobronchial or transbronchial biopsy. The diagnostic yield for a focal endobronchial lesion is 90% to 100%, whereas the diagnostic yield for a more peripheral focal lesion, using guidance with fluoroscopy and by obtaining additional cytology samples, is 40% to 80%. Obviously, some lesions are too peripheral for bronchoscopic sampling and require transthoracic needle biopsy or other procedure for diagnosis. The overall diagnostic yield for diffuse lung diseases by transbronchial biopsy is 37%.