Pleural Cryobiopsy and Frozen Section During Medical Thoracoscopy for Undiagnosed Pleural Effusion: A Prospective Observational Study

Abstract

Pleural effusion may remain undiagnosed after repeated pleural fluid evaluation, necessitating pleural tissue sampling. This prospective observational study evaluated the diagnostic yield of pleural cryobiopsy and the diagnostic performance of frozen section during medical thoracoscopy. Twenty consecutive adults with pleural effusion that remained undiagnosed after cytological and biochemical analysis were enrolled at a tertiary care center from February 2022 to February 2023. Medical thoracoscopy under general anesthesia was followed by targeted pleural cryobiopsy; specimens underwent frozen-section and final histopathological examination. Pleural mass lesions were the most frequent thoracoscopic finding (8/20, 40%), followed by a sago-grain appearance (5/20, 25%). Final histopathology yielded a definitive diagnosis in 18/20 (90%) patients; granulomatous pleuritis interpreted in the source study as tuberculosis and malignancy were each identified in 9/20 (45%). Adenocarcinoma was the most frequent malignant diagnosis (7/20, 35%). Frozen section yielded a diagnosis in 15/20 (75%) patients. Against final histopathology, frozen section showed a sensitivity of 83.3%, specificity of 100%, positive predictive value of 100%, negative predictive value of 40%, and overall accuracy of 85%. Pleural cryobiopsy during medical thoracoscopy achieved a high diagnostic yield in this small series, while frozen section provided rapid intra-procedural diagnostic information with high specificity. Larger comparative studies are needed to define the incremental value of cryobiopsy and frozen section in undiagnosed pleural effusion.