High-grade neuroendocrine carcinomas (HG-NECs) are aggressive malignancies, characterized by a high proliferative index (Ki-67 > 55%), poor differentiation, and rapid progression, distinguishing them from well-differentiated NETs, which have lower mitotic rates, better differentiation, and relatively favorable prognoses [10]. The gene discussed is MKI67; the disease is neuroendocrine carcinoma.