WHO 神经内分泌肿瘤分类的第五版旨在实现统一的术语并定义不同解剖位置的类似诊断方案。与第四版不同的是，引入了一章讨论非神经内分泌器官中的神经内分泌肿瘤，提出了一种二元分类系统，用于区分高分化肿瘤（称为神经内分泌肿瘤（NET））和低分化肿瘤（称为神经内分泌癌（NEC）） ）。 NET 的分级系统基于有丝分裂指数和/或 Ki-67 指数和/或坏死，具体取决于不同的位置。如果已经在消化系统中得到很好的应用，这种方法将修改和统一泌尿道、女性生殖器官和男性生殖系统神经内分泌肿瘤的分类。在肺和胸腺中，类癌/NET 双重术语已在世界卫生组织胸部肿瘤分类第五版中引入，并得到认可。这种方法无疑有助于多学科方法对受这些肿瘤影响的患者进行诊断和临床管理，而不会失去影响不同解剖部位肿瘤的临床和生物学行为的部位特异性特征。世卫组织新计划的其他主要进展是流行病学数据的同质化以及未来前瞻性研究数据的正确整合，这些研究旨在定义分子谱并确定肿瘤类型特异性和患者特异性治疗方法。

The 5th Edition of WHO classification of neuroendocrine neoplasms is built to achieve a uniform terminology and to define a similar diagnostic scheme across different anatomical locations. At variance with the 4th edition, a chapter discussing neuroendocrine neoplasms in non-neuroendocrine organs has been introduced, that proposes a binary system for classification segregating well differentiated neoplasms, termed neuroendocrine tumors (NET), and poorly differentiated neoplasms, termed neuroendocrine carcinomas (NEC). A grading system for NET is based on mitotic index and/or Ki-67 index and/or necrosis, depending on the different location. If already well-established in the digestive system, this approach modifies and homogenize the classification of neuroendocrine neoplasms in the urinary tract, in female genital organs and in the male genital system. In the lung and thymus, the double terminology of carcinoid/NET, already introduced in the 5th Edition of the WHO classification of thoracic tumors, is endorsed. This approach undoubtedly helps the multidisciplinary approach for the diagnosis and clinical management of patients affected by these neoplasms, without losing site-specific characteristics that influence the clinical and biological behavior of tumors in different anatomical sites. Other major advances of the new WHO scheme are the homogenization of epidemiological data and the correct integration of data from prospective future studies aimed at the definition of molecular profiles and at the identification of tumor type-specific and patient-specific therapeutic approaches.