Significance of microscopic invasion into hilar peribronchovascular soft tissue in resection specimens of primary non-small cell lung cancer

IntroductionThe significance and handling of microscopic invasion of non-small cell lung cancer (NSCLC) into hilar peribronchovascular soft tissue (SHEATH+) have not been defined in the TNM classification by AJCC/UICC; nevertheless, SHEATH+ may be equivalent to spread into the mediastinum. Also, assessment of the margin of peribronchial resection is challenging because of the technical difficulty of inking, and intraoperative and postoperative artifacts.MethodsRecords of 592 consecutive Asian patients with primary NSCLC (excluding adenocarcinoma in situ) who had, without any preoperative therapy, undergone lobectomy, sleeve lobectomy and pneumonectomy were examined. SHEATH+, simply defined as invasion of hilar peribronchovascular soft tissue, without categorizing any invasive patterns, and its significance were statistically analyzed.ResultsForty-four SHEATH+ cases demonstrated significantly advanced TNM stages, and were statistically associated with central occurrence, pN1-3, and vascular invasion, as assessed by logistic regression analysis. No statistically significant differences were observed between TNM stage-adjusted frequency of recurrence and recurrence-free intervals. Kaplan–Meier's estimates of the rate of overall and recurrence-free survival after surgery showed no statistically significant differences between SHEATH+ and SHEATH−. Cox's multivariate analysis suggested SHEATH was not a statistically independent prognostic factor under the TNM classification by AJCC/UICC (7th edition).ConclusionsSHEATH+ in NSCLC was simply associated with central occurrence and advanced TNM stages. To the best of our knowledge, this is the first report on the significance of SHEATH+ in NSCLC.