The Significance of Skip Mediastinal Lymph Node Metastasis in the Prognosis of Patients with Resected Non-Small-Cell Lung Carcinoma: Is It Really a Better N2 Disease Subtype?

Objective: In this study, we aimed to reveal the prognostic differences between skip and non-skip metastasis mediastinal lymph node (MLN) metastasis. Methods: A total of 202 patients (179 males and 23 females; mean age, 59.66 ± 9.89 years; range: 29–84 years) who had ipsilateral single-station MLN metastasis were analyzed in two groups retrospectively between January 2009 and December 2017: “skip ipsilateral MLN metastasis” group (sN2) (n = 55,27.3%) [N1(–), N2(+)], “non-skip ipsilateral MLN metastasis” group (nsN2) (n = 147,72.7%) [N1(+), N2(+)]. Results: The mean follow-up was 42.63 ± 34.91 months (range: 2–117 months). Among all patients, and in the sN2 and nsN2 groups, the median overall survival times were 63.5 ± 4.56, 68.8 ± 7, and 59.3 ± 5.35 months, respectively, and the 5-year overall survival rates were 38.2%, 46.3%, and 36.4%. Conclusion: Skip metastasis did not take its rightful place in TNM classification; thus, further studies will be performed. To detect micrometastasis, future studies on skip metastasis should examine non-metastatic hilar lymph nodes (LNs) through staining methods so that heterogeneity in patient groups can be avoided, that is, to ensure that only true skip metastasis cases are included. Afterwards, more accurate and elucidative studies on skip metastasis can be achieved to propound its prognostic importance in the group of N2 disease.