The usefulness of full-thickness biopsy during semirigid pleuroscopy for differentiating between malignant pleural mesothelioma and benign conditions

<bold>Background:</bold> Malignant pleural mesothelioma (MPM) is a rare disease with a poor prognosis, and histological differentiation between MPM and benign conditions (BCs) based on the presence of tumor cell invasion into adipose tissue is crucial for determining the appropriate treatment strategy. This study aimed to evaluate the utility of full-thickness biopsy (FTB) during semirigid pleuroscopy under local anesthesia for differentiating between MPM and BCs. <bold>Methods:</bold> Consecutive patients who underwent FTB with an insulated-tip diathermic knife and/or a cryoprobe during semirigid pleuroscopy to differentiate between MPM and BCs from April 2019 to October 2023 were retrospectively enrolled from our institution. The diagnostic accuracy of FTB for diagnosing MPM was evaluated. <bold>Results:</bold> Of the 117 cases that underwent semirigid pleuroscopy, 36 cases underwent FTB to differentiate between MPM and BCs. Except for 8 cases diagnosed as lung cancer, 14 cases were ultimately diagnosed with MPM (eight epithelial types, four sarcomatoid types, and two biphasic types) and BCs, respectively. Each of the 13 MPM and BCs was histologically diagnosed by FTB, and their clinical courses were consistent with the diagnoses. One false-positive and one false-negative case of MPM occurred. The sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy for diagnosing MPM were all 0.929. There were no severe complications associated with the procedures. <bold>Conclusions:</bold> FTB during semirigid pleuroscopy has a high diagnostic utility that accurately differentiates between MPM and BCs.