Factors associated with discrepancy between fresh frozen and permanent biopsy from medical thoracoscopy: single center analysis of 172 medical flexible thoracoscopy cases

Background Frozen sections prepared during medical thoracoscopy (MT) have precise diagnostic ability in pleural pathology and may assist in decision-making before pleurodesis. The present study evaluated the diagnostic sensitivity of frozen sections from flex-rigid MT, and further evaluated clinical parameters for their association with a discrepancy between frozen sections and permanent paraffin sections. Methods This retrospective study evaluated 172 patients who underwent flex-rigid MT between February 2017 and November 2019 at Incheon Saint Mary's Hospital. Results Of the 172 patients, 85 were pathologically diagnosed with malignancy based on permanent paraffin sections. An accurate diagnosis by fresh frozen section was feasible in 88.2% of the cases compared to the permanent paraffin sections. Among the 85 patients, 75 had malignancies in frozen sections, while 10 patients showed otherwise. In the 85 malignant cases, age, sex, the volume of effusion, thoracoscopic findings, as well as the final pathological diagnosis (lung vs. non-lung origin) were included in univariate analysis for an association with non-malignant frozen section results. High adhesion grade and malignancy other than lung cancer were significant factors associated with frozen section negative cases in a multivariable analysis. Conclusions Taking fresh frozen sections during MT using a flex-rigid bronchoscope is a useful diagnostic modality with reliable sensitivity for malignancy. However, if the pre-procedural diagnosis is likely to be a malignancy other than lung cancer, and if severe adhesions are present in the pleural cavity, the final pathological confirmation should be determined based on permanent paraffin sections, not only on fresh frozen sections.