Recognizing this void in the literature, the main objectives of this study were to: i) compare mitotic rate and Ki-67 index using transcriptomic data in neuroendocrine samples, and ii) identify the strongest indicator of the biological behavior among the histological subtypes of neuroendocrine tumors, i.e., carcinoids and LCNEC’s. The gene discussed is MKI67; the disease is large cell neuroendocrine carcinoma.