Dual-Block Elastic Stain Significantly Increasing Visceral Pleural Invasion(VPI) Positivity and Analysis of Potential Predictors of VPI in Peripheral Non-Small Cell Lung Cancer

Abstract Background: Visceral pleural invasion (VPI) is a critical component in the staging of peripheral non–small cell lung carcinoma (NSCLC). Single tumor tissue block for elastic stain is conducive to identifying pleural invasion in routine pathologic examination. We aim to investigate whether dual-block elastic stain increase VPI positivity compared with single-block elastic stain, further analyze the potential predictors of VPI status.Methods: Resected 8419 consecutive peripheral NSCLC cases including tumor size≤3cm 6008 patients were retrospectively reviewed. Total cases were divided into a cohort using one tumor tissue paraffin block (single-block group, n=5184) and a cohort using dual tumor tissue paraffin blocks (dual-block group, n=3235) for elastic stain. Each case was performed with Victoria-blue van Gieson staining to assess VPI status. The clinicopathologic features of patients were collected from the electronic medical record system.Results: The overall incidence of VPI was 12.4% (1047/8419) in peripheral NSCLC patients. The VPI positivity detected by dual-block elastic stain was significantly higher than that by single-block elastic stain (17.7% (573/3235) v.s. 9.1% (474/5184), P＜0.001). The presence of VPI in T1 ≤3cm patients detected by single and dual block elastic stain was 6.3% (235/3730) and 12.0% (273/2278), respectively (P＜0.001). Therefore, 5.7% T1 patients (stage IA) are additionally upstaged to T2a (stage IB) by dual block elastic stain. But the incidence of VPI in pT2a patients had no significant difference between single-block group and dual-block group (16.8% vs 17.1%, P=0.916). The lymphovascular invasion, lymph node metastasis, poor differentiated carcinomas and the presence of STAS status could be well significant predictors of VPI (P＜0.001). Area under the ROC curve of adenocarcinoma morphology was 0.263 for lepidic pattern, 0.544 for acinar and papillary pattern, and 0.720 for micropapillary and solid pattern in predicting invasion of pleura.Conclusion: Our results indicated that using dual-block elastic stain identify more VPI positive T1 NSCLC patients who are upstaged to T2a and could benefit from optimal management after post-operation. The application of dual-block elastic stain is an efficient and practical method to detect VPI, especially for patients with high-risk prognostic factors.