Recent advances in the diagnosis and treatment of lung cancer have dramatically improved the therapeutic landscape [1]. A deeper understanding of the disease pathophysiology and the identification of oncogenic driver mutations have increased the adoption of targeted therapy and immune checkpoint inhibitors [2], [3]. Adequate biopsy samples are required for accurate diagnosis and molecular analysis. These components are vital in determining suitable treatment [4].

Biopsy specimens from patients with lung cancer are typically procured using bronchoscopic or computed tomography (CT)-guided procedures. Transbronchial biopsy (TBB) is the preferred method for the collection of samples from the lower airway mucosa, alveolar tissue, and surrounding interstitial tissue. Occasionally, mesothelial cells may also be acquired during TBB [5]. Mesothelial cells are epithelial-like cells that line the pleura, pericardium, and peritoneum [6]. These cells are referred to as “atypical epithelium” owing to their differences from normal alveolar epithelial cells, which may complicate the pathological diagnosis and lead to misidentification as cancer cells. Nevertheless, the prevalence and clinical significance of mesothelial cells in TBB specimens remain inadequately explored, with few prior investigations. To shed light on the patterns of mesothelial cells in TBB specimens and the associated risk of misdiagnosis, we reviewed cases in which mesothelial cells were identified within such specimens.