MKI67 and neoplasm: Pancreatic neuroendocrine tumors (PNETs) are a rare heterogeneous group of neoplasms [1] that have been classified into two broad categories based on the combination of morphological features and proliferation grading system (G), assessed by the Ki-67 index [1]: well-differentiated PNET G1 (Ki-67 index ≤2%) and G2 (Ki-67 index: 3–20%) and poorly differentiated pancreatic neuroendocrine carcinoma PNEC - G3 (Ki-67 > 20%).