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digestive neuroendocrine tumors

Friday 19 September 2014

Neuroendocrine tumors of the gastrointestinal tract; digestive neuroendocrine neoplasms

Classification

In 2000, the World Health Organization (WHO) classification replaced “carcinoid” with the terms neuroendocrine tumors and neuroendocrine carcinomas to describe gastrointestinal neoplasms originating from the diffuse system of neuroendocrine cells.

Along with developing tumor node metastasis staging and grading systems, the WHO classification provides an improved system for determining prognosis and treatment and includes three main groups subdivided by organ of tumor origin:
- (1) well differentiated neuroendocrine tumors (benign behavior or uncertain malignant potential-“carcinoids”);
- (2) well differentiated neuroendocrine carcinomas (low-grade malignancy-“malignant carcinoids”);
- (3) poorly-differentiated carcinomas (high-grade malignancy).

This classification replaces the previous outdated system which was based on embryologic cell of origin (foregut, midgut, hindgut) and shared little correlation between tumor behavior and tumor location especially for neoplasms originating in the foregut (tracheobronchopulmonary, gastric, and pancreatic tumors).

Histologically, tumor proliferation capacity is measured by Ki-67 staining with Ki-67 Index @<@ 2% seen in grade I tumors, 2%-20% in grade II tumors, and > 20% tumor cell involvement in grade III GEP-NET.

Cells originating from the diffuse system of neuroendocrine cells within the gastrointestinal tract share phenotypic similarities with neural cells in their expression of synaptophysin, NSE, and chromogranin A.

Many tumors remain clinically silent and may present with intestinal obstruction as a result of tumor-induced fibrosis rather than signs or symptoms of secretory products.

The classic carcinoid syndrome (cutaneous flushing and secretory diarrhea) occurs in less than 10% of patients and typically in the setting of hepatic metastases.

Open references

- Neuroendocrine tumors of the gastrointestinal tract: Case reports and literature review. Salyers WJ, Vega KJ, Munoz JC, Trotman BW, Tanev SS. World J Gastrointest Oncol. 2014 Aug 15;6(8):301-10. doi : 10.4251/wjgo.v6.i8.301 PMID: 25132927 [Free]