The role of rapid IHC in elevating STAS diagnostic accuracy during intraoperative frozen section for lung adenocarcinoma

Aim The aim of this study was to evaluate whether the utility of cytokeratin (AE1/AE3) rapid immunohistochemistry (IHC) in combination with haematoxylin–eosin (H&E) staining improves the intraoperative diagnosis of spread through air spaces (STAS) on frozen sections (FS). Methods and results This study included 153 patients. Three pathologists independently evaluated STAS on FS using either HE staining alone or in combination with rapid IHC, with postoperative paraffin sections serving as the gold standard. Sensitivity and specificity were compared, along with interobserver and intraobserver agreement (κ values), diagnostic time, and causes of misdiagnosis. Compared with HE alone, HE combined with rapid IHC staining increased mean diagnostic sensitivity from 73.7% to 87.8% and specificity from 85.5% to 89.9% across pathologists with varying levels of experience. Mean intraobserver agreement improved from κ = 0.644 (83.9%) to κ = 0.907 (95.9%), and mean interobserver agreement improved from κ = 0.485 (65.0%) to κ = 0.671 (77.2%). Average diagnostic time decreased from 2 min 53–23 s. Misdiagnoses were primarily attributable to a limited number of STAS clusters, confusion with macrophages, and artefacts. Conclusions Intraoperative H&E combined with rapid IHC enhanced the sensitivity and specificity of STAS detection, improved interobserver/intraobserver agreement and reduced diagnostic time during FS evaluation without significantly extending the overall intraoperative FS processing time. Nevertheless, additional multicenter validation is required.