Unmet needs in high-grade gastroenteropancreatic neuroendocrine neoplasms (WHO G3)

Gastroenteropancreatic (GEP) neuroendocrine neoplasms (NEN) are classified based on morphology and graded based on their proliferation rate as either well-differentiated low-grade (G1 to G2) neuroendocrine tumors (NET) or poorly differentiated high-grade (G3) neuroendocrine carcinomas (NEC). Recently, a new subgroup of well-differentiated high-grade pancreatic tumors (NET G3) has been defined. The GEP NEN G3 group consisting of both NEC and NET G3 has recently been shown to be a quite heterogeneous patient group concerning prognosis and treatment benefit, depending on factors such as the primary tumor site, differentiation, proliferation rate, and molecular alterations. In this review we discuss the existing data on diagnostics, treatment, and biomarkers in this patient group, the unmet needs, and the future perspectives.