Classification of Neuroendocrine Tumors

In this episode, panelists discussed classification of neuroendocrine neoplasms. Over the years, the classification of neuroendocrine neoplasms has evolved significantly, improving diagnostic accuracy and guiding clinical management. The 2010 WHO classification first introduced a universal, proliferation-based grading system using Ki-67 to categorize tumors into grades 1–3, providing a reproducible metric for prognosis and treatment selection. In 2017, the system was updated to recognize well-differentiated grade 3 neuroendocrine tumors (NETs) as distinct from poorly differentiated neuroendocrine carcinomas, with implications for therapy—such as differentiating between platinum-based and temozolomide-based regimens. By 2019, this dual-axis model of grade and differentiation was standardized across all gastroenteropancreatic NENs, improving consistency in diagnosis and imaging approaches. The 2022 WHO update further refined terminology, integrated molecular features (e.g., TP53, RB, DAXX, ATRX), and expanded classification to other endocrine organs. These updates have enhanced uniformity in pathology reporting and supported more precise, personalized treatment decisions.