Although our findings are of significant interest from a biological point of view, there were some limitations, which include, i) Sample size: due to small sample size of the LCNEC group, the gene-level and pathway-level associations with mitotic rate and Ki-67 index is less robust; ii) Inter-observer variability: there is a considerable interobserver variation in the histopathological characterization of lung NET’s, i.e., in samples with low to medium values of mitotic index [12]. This evidence concerns the gene MKI67 and lung neuroendocrine neoplasm.