Whereas well-differentiated NEN have mostly favorable prognosis, poorly differentiated NEN (neuroendocrine carcinoma, NEC) are highly proliferative (Ki67 index > 20%) with a median overall survival of 11–17 months (Rinke and Gress 2017; Rindi et al. 2022). This evidence concerns the gene MKI67 and neuroendocrine carcinoma.