Although insulinomas are typically well-differentiated neuroendocrine tumors with low proliferative activity, our case revealed a Ki-67 index of 21%, which places it at the upper limit for grade 3 tumors according to the WHO classification and NCCN Guidelines for Neuroendocrine and Adrenal Tumors [20,21]. The gene discussed is MKI67; the disease is neuroendocrine neoplasm.