Feasibility of Histological Grading System of Small-sized Pulmonary Adenocarcinoma Based on Frozen Section as a Predictor for Nodal Metastasis.

Accurate prediction of lymph node metastasis is the key to selecting the best surgical approach for clinical stage N0 small-sized invasive pulmonary adenocarcinoma, especially when sublobar resection is considered. This study aimed to explore the potential use of the International Association for the Study of Lung Cancer (IASLC)-graded intraoperative frozen section analysis in guiding thoracic surgeons toward optimal surgical decisions, particularly for lymph node procedures. In this retrospective study, we analyzed 190 invasive pulmonary adenocarcinomas staged clinically as N0, with tumors ≤2 cm and a consolidation-tumor ratio >0.5 on computed tomography, resected with intraoperative frozen section analysis between January 2015 and December 2022. The IASLC grade of frozen sections was evaluated by 3 independent pathologists. Interobserver agreement, concordance with corresponding permanent sections, and the association between the grade and lymph node metastasis were then assessed. Interobserver agreement of the IASLC grading on frozen sections among 3 pathologists was substantial (κ = 0.68). The overall concordance rate between the frozen and permanent sections for IASLC grade was 75.8%, with grade 3 tumors showing particularly high concordance (95.8%). While the sensitivity for detecting grade 3 tumors in frozen sections was 69.8% (60/86), as confirmed by permanent section diagnosis, the specificity was high at 97.1% (101/104), emphasizing the potential diagnostic value of frozen sections for accurately identifying grade 3 tumors. Moreover, multivariate analysis using preoperative and intraoperative characteristics identified IASLC grading of frozen sections as the only independent factor statistically associated with lymph node metastasis, characterized by an odds ratio of 4.34 (95% CI, 1.54-12.2; P = .006). Therefore, histological grading of frozen sections could serve as a predictor of lymph node metastasis and provide valuable information for thoracic surgeons when considering the surgical approach in small-sized lung adenocarcinomas (≤2 cm and consolidation-tumor ratio >0.5).