A novel immunohistochemical staining method of frozen sections improves the intraoperative diagnosis of Sclerosing Pneumocytoma and bronchiolar adenoma

Sclerosing Pneumocytoma (SP) and Bronchial Adenoma (BA) are rare benign tumors that are morphologically difficult to differentiate from lung adenocarcinoma during intraoperative diagnosis. Effective IHC on frozen section might be beneficial for their recognition. This study introduced a novel IHC method that could be applied to intraoperative frozen sections. Its performance was well demonstrated, and the improvement in pathological diagnosis and surgical decisions was analyzed. Comparative cohorts of SP and BA were established from surgical samples. The influence of the novel method was analyzed using self-controlled samples. The diagnostic efficacy of the novel IHC on frozen sections was tested using selected markers. The impact of IHC using frozen sections on the pathological evaluations and surgical operations was analyzed. The new IHC protocol on frozen sections demonstrated superior performance. Compared to IHC on FFPE, the overall accuracy of the selected markers was satisfactory. It improved the diagnostic accuracy of junior pathologists, with the correct diagnosis rate increasing from 38.7% to 93.6% in SP and from 49.1% to 94.5% in BA. Additionally, the rate of lobectomy and segmentectomy decreased from 54.2% to 38.7% in the SP cohort. A unique group featuring single-layered bronchiolar adenomatoid lesions was described. The optimized IHC protocol for frozen sections enhances intraoperative diagnostic accuracy, facilitating improved surgical decision-making for SP and BA, thereby enhancing the management of diseases that require accurate intraoperative diagnosis. The clinical application of the new IHC method and the special group of adenomatoid lesions warrant further investigations.