The definitive histological examination revealed a neuroendocrine tumor with insulin receptors (insulinoma) of 3.5 cm infiltrating the duodenum, retroperitoneal adipose tissue, with widespread neoplastic thrombosis, and with metastasis in 3 pancreatic-duodenal lymph nodes among the 48 that had been surgically removed (T3N1MO, AjCC VIII edition G1), with a low replicative index (Ki67: 2%); radical resection (R0). Vascular and adipose tissue infiltration by the tumor, which are indicative of malignancy, were observed. The gene discussed is MKI67; the disease is pancreatic insulinoma.