Introduction

Lung cancer is the second most common cancer worldwide [1]. Lung cancer screening with low dose CT (LDCT) scans demonstrated a survival bene t in high-risk groups [2]. Among other routine cancer screening modalities, the numbers needed to screen (NNS) to prevent one death for LDCT is 320 [2]. However, a high proportion of false-positive nodules on LDCT scans necessitates a carefully implemented follow-up plan based on the patient's probability of malignancy. As the number of lung nodule detection on LDCT increases, there is an increasing demand to perform tissue biopsy of lung nodules. Generally, there are three options for tissue biopsy of the lung nodule: surgical resection, CT-guided transthoracic needle biopsy (CT-TTNB), and transbronchial biopsy (TBBx). In lung cancer patients, there is a high proportion of patients with poor lung function are also at risk for complications following surgical or percutaneous biopsy. CT-TTNB, through meta-analyses, has been

D. Khemasuwan (*)

Pulmonary and Critical Care Division, Virginia Commonwealth University, Richmond, VA, USA e-mail: danai.khemasuwan@vcuhealth.org

A. C. Mehta

Lerner College of Medicine, Buoncore Family Endowed Chair in Lung Transplantation, Respiratory Institute, Cleveland Clinic, Cleveland, OH, USA e-mail: Mehtaa1@ccf.org

shown to have excellent diagnostic yield up to 92% [3]; however, it is frequently complicated by pneumothorax requiring chest tube placement and hospitalization in half of the subjects [4, 5].

TBBx is one of the minimally invasive procedures which is frequently used to determine the etiology of solitary pulmonary nodules (SPN). However, when it comes to the nodules located in the peripheral one-third of the lung and less than 2 cm in diameter, the procedure is of limited value and establishing the diagnosis remains challenging. TBBx has historically had a low diagnostic yield, with diagnostic rates for nodules under 2 cm estimated to be 34% and still only 63% for lesions over 2 cm [6]. In addition, TBBx has reached its plateau in terms of its diagnostic yield for the SPN. In most instances the diagnostic yield is limited by an inability to steer biopsy tools directly to the lesion. The sensitivity of bronchoscopy for diagnosing etiology of a SPN depends on several factors including (1) the size of the nodule; (2) the proximity of the nodule to the central airway; and (3) the prevalence of cancer in the study population. If the CT reveals a positive “bronchus sign” the diagnostic yield of TBBx increases up to 72%; unfortunately, not a common occurrence for smaller lesions [7].

Although the addition of radial probe endobronchial ultrasound (rp-EBUS) to the traditional bronchoscopy has improved the diagnostic yield, its usefulness is technically limited as the ultrasound probes cannot be easily steered beyond the