Clinical implications of uncertain resection in scenarios of metastasis of the highest or most distant mediastinal lymph node station following surgical treatment of non-small-cell lung cancer

•The positive highest mediastinal LN is one of the criteria of uncertain resection.•The positive highest or most distant mediastinal LN was not related to poor survival.•The subcategories of N2 and T stage were highly associated with overall survival. The positive highest nodal station after operation is one of the definitions of “uncertain resection” proposed by the International Association for the Study of Lung Cancer. This study was performed to determine the prognostic value of positive highest or the most distant nodal station in patients with N2 non-small-cell lung cancer (NSCLC). Three hundred thirty-nine patients who underwent complete anatomical resection and mediastinal lymph node (LN) dissection for N2 NSCLC between 2000 and 2015 were reviewed. Cases of operative mortality, extracapsular invasion of LN and incomplete resection were excluded from analysis. The mean age was 61.58 ± 9.43 years, and 235(69.3%) patients were male. The numbers of total dissected LNs and positive LNs were 29.90 ± 11.92 and 5.49 ± 5.90, respectively. The subcategory of N stage was divided as follows: N2a1, 91(26.8%); N2a2, 132(38.9%); and N2b, 116(34.2%). One hundred forty-two (41.9%) patients showed highest LN metastasis, and 162(47.8%) patients showed most distant LN metastasis. Kaplan–Meier analysis revealed no differences between distant LN negative and positive patients regarding 5-year overall survival (43.1% vs. 39.2%; p = 0.428) and between highest LN negative and positive patients regarding 5-year overall survival (42.1% vs. 40.0%; p = 0.539). On multivariable analysis, metastasis to the most distant mediastinal LN (hazard ratio (HR): 1.050; p = 0.755) and metastasis to the highest mediastinal LN (HR: 1.015; p = 0.924) were not related to overall survival. The current definition of uncertain resection based on metastasis of the highest or most distant LNs did not show survival differences in completely resected N2 NSCLC.