The current WHO classification system is organized by the tumor’s growth rate (with a Ki-67 fraction of < 3% representing grade 1 (G1), 3–20% grade 2 (G2), and > 20% grade 3 (G3)) and also discriminates between well-differentiated tumors and poorly differentiated carcinomas.[2] Whereas low-grade NEN are malignancies with a near to normal life expectancy,[3] the clinical management of high-grade NEN remains challenging. This evidence concerns the gene MKI67 and neoplasm.