Benign Mesothelial Cells in transbronchial biopsy specimens: A potential diagnostic pitfall for lung cancer

Bronchoscopy is a common diagnostic procedure used to identify lung cancer. Specimens acquired through transbronchial biopsy are pivotal in the diagnosis and molecular characterization of this disease. The occurrence of benign mesothelial cells during a transbronchial biopsy (TBB) is relatively rare. Furthermore, these lesions can sometimes be erroneously identified as malignant, potentially resulting in unwarranted or inappropriate treatment for patients with and without lung cancer. In this retrospective analysis, we examined 619 TBB cases at our institute from 2019 to 2021. Benign mesothelial cells were identified via immunohistochemical studies in eight (1.3%) of 619 cases. These cells were classified into three patterns based on their cellular morphology: monolayer, lace, and cobblestone. Recognizing this phenomenon during the procedure is crucial to accurately distinguish benign mesothelial cells from their cancerous counterparts.