open access: Pathology Reporting of Neuroendocrine Tumors: Essential Elements for Accurate Diagnosis, Classification, and Staging

Pathology Reporting of Neuroendocrine Tumors

".... Epithelial neuroendocrine tumors (NETs) can arise in most epithelial organs of the body but are particularly well-recognized in the lung, tubular gastrointestinal tract, and pancreas. Oberndorfer proposed the term “carcinoid tumor” for well-differentiated NETs more than a century ago,¹ and for many years this term was employed for most entities in the family, although those arising in the pancreas were designated “islet cell tumors.”², ³, ⁴, ⁵ Since Oberndorfer's time, it has become clear that NETs comprise a diverse group of neoplasms in terms of origin, mechanism of development, functional status, histologic patterns, and biological behavior. Most studies have focused on subsets of tumors restricted to one organ or organ system,⁶, ⁷, ⁸ resulting in many different diagnostic terms and classification systems. For example, “neuroendocrine tumor,” “carcinoid tumor,” “endocrine neoplasm,” and “neuroendocrine carcinoma” have all been applied to small intestinal primary tumors.³, ⁹, ¹⁰, ¹¹, ¹² These varied approaches have obscured some of the commonalities among NETs of different sites, and comparison of data among studies employing different nomenclature and classification parameters has been difficult.^13......