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Neuroendocrine neoplasms of the digestive system – current classification and terminology
Affiliations- Department of Endocrinology and Internal Medicine, Faculty of Medicine and Health Sciences, Andrzej Frycz Modrzewski Krakow University, Krakow, Poland
- The University Hospital in Krakow, Krakow, Poland
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Abstract
The system of classification and terminology of neuroendocrine neoplasms (NENs), updated in 2017 by AJCC and in 2019 by WHO, is now recommended for general use. This article is a review of this classification with respect to NENs of the digestive tract. Within the new system, two categories of neuroendocrine neoplasms of the digestive system were introduced, differing in morphology, clinical course and treatment, as based on differentiation and histological maturity grading (G). Among NENs of the digestive tract, well differentiated neuroendocrine tumours, with Ki-67 proliferation index below 20%, NET G1 and NET G2, histologically resembling normal neuroendocrine cells were distinguished. Neuroendocrine neoplasms with Ki-67 above 20% – termed neuroendocrine carcinoma NEC (poorly differentiated carcinoma G3) – were found to be heterogeneous. In every organ of the digestive tract a limited group of well differentiated tumours with Ki-67 above 20%, but typically less than 55% (well differentiated high grade NET G3) was distinguished. The remaining poorly differentiated neuroendocrine neoplasms with Ki-67 above 20%, usually over 55%, were classified as NEC (high grade neuroendocrine carcinoma). Within NEC, two groups were distinguished – large cell and small cell carcinomas. By introducing this new classification based on clinical and molecular research, any confusion between NET G3 and NEC is avoided. NEC, goblet-cell carcinoid of the appendix and MiNEN, which should be classified according to criteria applied to adenocarcinomas of their respective organs of the digestive system, are not discussed.
Abstract
The system of classification and terminology of neuroendocrine neoplasms (NENs), updated in 2017 by AJCC and in 2019 by WHO, is now recommended for general use. This article is a review of this classification with respect to NENs of the digestive tract. Within the new system, two categories of neuroendocrine neoplasms of the digestive system were introduced, differing in morphology, clinical course and treatment, as based on differentiation and histological maturity grading (G). Among NENs of the digestive tract, well differentiated neuroendocrine tumours, with Ki-67 proliferation index below 20%, NET G1 and NET G2, histologically resembling normal neuroendocrine cells were distinguished. Neuroendocrine neoplasms with Ki-67 above 20% – termed neuroendocrine carcinoma NEC (poorly differentiated carcinoma G3) – were found to be heterogeneous. In every organ of the digestive tract a limited group of well differentiated tumours with Ki-67 above 20%, but typically less than 55% (well differentiated high grade NET G3) was distinguished. The remaining poorly differentiated neuroendocrine neoplasms with Ki-67 above 20%, usually over 55%, were classified as NEC (high grade neuroendocrine carcinoma). Within NEC, two groups were distinguished – large cell and small cell carcinomas. By introducing this new classification based on clinical and molecular research, any confusion between NET G3 and NEC is avoided. NEC, goblet-cell carcinoid of the appendix and MiNEN, which should be classified according to criteria applied to adenocarcinomas of their respective organs of the digestive system, are not discussed.
Keywords
neuroendocrine neoplasms; NET; NEC; G grading system; TNM classification; staging
About this articleTitle
Neuroendocrine neoplasms of the digestive system – current classification and terminology
Journal
Nowotwory. Journal of Oncology
Issue
Article type
Review paper
Pages
26-37
Published online
2021-02-05
Page views
596
Article views/downloads
1444
DOI
Bibliographic record
Nowotwory. Journal of Oncology 2021;71(1):26-37.
Keywords
neuroendocrine neoplasms
NET
NEC
G grading system
TNM classification
staging
Authors
Agata Bałdys-Waligórska
Andrzej Nowak