Precise sublobar lung resection for small pulmonary nodules: localization and beyond.

Early-stage primary lung cancer is increasingly detected by computed tomographic (CT) screening and the radicality of sublobar lung resection (wedge resection and segmentectomy) has been suggested. However, identification of a tumor intraoperatively becomes more difficult, the earlier a nodule is detected. A solution to this challenge is localization techniques. There are many techniques to localize small pulmonary nodules, including that replacing surgeon's tactile sensation, visualizing the tumor using ultrasound, and various types of lung markings that are placed percutaneously under CT guidance or bronchoscopically. The most commonly used technique is CT-guided placement of a hookwire, but there are concerns about potentially fatal air embolism. Bronchoscopic localization, especially using electromagnetic navigation bronchoscopy with or without intraoperative cone-beam CT imaging, has been increasingly reported. Beyond localization, the concept of lung "mapping" is emerging. In sublobar lung resection, in addition to localization of the targeted tumor, acquisition of sufficient resection margins is critical to prevent local recurrence. Virtual-assisted lung mapping (VAL-MAP) has evolved from bronchoscopic dye localization, but by placing multiple dye marks, it provides two-dimensional geometric information on the lung. Moreover, to ensure deep resection margins, the newly developed technique of VAL-MAP 2.0 combining dye marks and intrabronchial placement of a microcoil enables three-dimensional lung mapping. This allows for intraoperative navigation of lung resection under a fluoroscope. Development of this field, such as using a new technology of augmented reality, will further enhance the accuracy and convenience of lung resection in the near future.