Bronchoscopy for the diagnosis of peripheral lung lesions
Peripheral pulmonary lesions (PPLs) are generally considered as lesions in the peripheral one-third of the lung although a precise definition and radiographic anatomical landmarks separating central and peripheral lesion does not yet exist. The radiographic detection of such lesions has increased significantly with the adoption of lung cancer screening programs. These lesions are not directly visible by regular flexible bronchoscopes as they are usually distal to the lobar and segmental bronchi. Traditionally, depending on location and clinical stage at presentation, these lesions were typically sampled by computerized tomography (CT) guided needle or surgical biopsy although some centers also used ultrasound and fluoroscopy guided percutaneous needle biopsy. Due to lack of direct visualization, the yield for bronchoscopic guided sampling especially of the small <2 cm pulmonary nodules was very low. Therefore, sampling has been preferentially performed by percutaneous CT guidance, which had high yield of above 90% but it comes at the cost of higher risk complications like pneumothorax with reported rate of 15% to 28%. Directly proceeding to surgical resection is also considered in appropriate candidates with high suspicion of malignancy without any evidence of distant metastasis but the proportion of such cases of lung cancer is low. The manuscript discussed the various bronchoscopic diagnostic modalities for peripheral pulmonary lesions. It is important to note that most of the studies in this field are relatively small, not randomized, suffer from selection bias, have considerable heterogeneity in sampling methodology/instruments and usually have been performed in high volume institutions by dedicated highly experienced proceduralists. The prevalence of malignancy in most of the reported cohorts has also been high which may result in higher diagnostic yields. All these factors need to be kept in mind before generalizing the results to individual centers and practices.