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WHO Classification of Tumours
Neuroendocrine tumor G2 (NET G2)
Colon and rectum


Definition

A neuroendocrine tumour (NET) is defined as a well-differentiated, neuroendocrine neoplasm composed of cells with features similar to those of the normal gut endocrine cell, expressing general markers of neuroendocrine differentiation (usually diffuse and intense chromogranin A and synaptophysin) and hormones (usually intense but not necessarily diffuse) according to site, with mild- to-moderate nuclear atypia and a low number of mitoses.
The proposed grading based on proliferation with the following definitions of mitotic count and Ki67 index:
G1 (NET G1) : mitotic count, <2 per 10 high power fields (HPF) and/or ≤2% Ki67 index;
G2 (NET G2): mitotic count 220 per 10 HPF and/or 320% Ki67 index

Click for details
Bosman FT, Carneiro F, Hruban RH, Theise ND (Eds.)
WHO Classification of Tumours of the Digestive System.
4th Edition
International Agency for Research on Cancer: Lyon 2010



.

Commentary: Neuroendocrine tumours of the digestive system

> Histological subtypes
Since the large bowel is derived from both the embryonic midgut and hindgut, NETs of the colon can be either midgut-type enterochromaffin cell (EC), serotonin-producing NET (in the caecum and ascending colon) or hindgut-type NETs that arise in the more distal colon and rectum and are L cell, Glucagon-like peptide-producing and PP/PYY-producing NETs [[864]]

Click for details
Bosman FT, Carneiro F, Hruban RH, Theise ND (Eds.)
WHO Classification of Tumours of the Digestive System.
4th Edition
International Agency for Research on Cancer: Lyon 2010



.

> NET of the presacral region
Neuroendocrine neoplasms of the presacral region are rare, with only 25 cases reported in the English literature

Click to access Pubmed
Dujardin F, Beaussart P, de Muret A, Rosset P, Waynberger E, Mulleman D, de Pinieux G (2009)
Primary neuroendocrine tumor of the sacrum: case report and review of the literature.
Skeletal Radiol 38: 819-23




Click to access Pubmed
Kim T, Grobmyer SR, Liu C, Hochwald SN (2007)
Primary presacral neuroendocrine tumor associated with imperforate anus.
World J Surg Oncol 5: 115




Click to access Pubmed
Liang JJ, Alrawi S, Fuller GN, Tan D (2008)
Carcinoid tumors arising in tailgut cysts may be associated with estrogen receptor status: case report and review of the literature.
Int J Clin Exp Pathol 1: 539-43




Click to access Pubmed
Luong TV, Salvagni S, Bordi C (2005)
Presacral carcinoid tumour. Review of the literature and report of a clinically malignant case.
Dig Liver Dis 37: 278-81




Click to access Pubmed
Song DE, Park JK, Hur B, Ro JY (2004)
Carcinoid tumor arising in a tailgut cyst of the anorectal junction with distant metastasis: a case report and review of the literature.
Arch Pathol Lab Med 128: 578-80



. An origin from hind - gut remnants in the region has been proposed, 12 of the reported cases being associated with teratoma or tailgut cysts, one case being associated with imperforate anus
Click to access Pubmed
Kim T, Grobmyer SR, Liu C, Hochwald SN (2007)
Primary presacral neuroendocrine tumor associated with imperforate anus.
World J Surg Oncol 5: 115



. Patients are more often female, age ranging from 18 to 72 years, presenting with mass-related symptoms and often pain. Neuroendocrine neoplasms of the presacral region are NETs displaying histological and immunohistochemical features similar to those of rectal NETs, with trabecular-gyriform structure, bland cytology and immunoreactivity for chromogranin A and synaptophysin [[746]]. One case also showed positive nuclear immunohistochemistry for estrogen and progesterone receptors
Click to access Pubmed
Liang JJ, Alrawi S, Fuller GN, Tan D (2008)
Carcinoid tumors arising in tailgut cysts may be associated with estrogen receptor status: case report and review of the literature.
Int J Clin Exp Pathol 1: 539-43



. The low mitotic rate, the absence of necrosis and the low Ki67 index reported qualify most presacral region NETS as G1
Click to access Pubmed
Dujardin F, Beaussart P, de Muret A, Rosset P, Waynberger E, Mulleman D, de Pinieux G (2009)
Primary neuroendocrine tumor of the sacrum: case report and review of the literature.
Skeletal Radiol 38: 819-23




Click to access Pubmed
Kim T, Grobmyer SR, Liu C, Hochwald SN (2007)
Primary presacral neuroendocrine tumor associated with imperforate anus.
World J Surg Oncol 5: 115




Click to access Pubmed
Liang JJ, Alrawi S, Fuller GN, Tan D (2008)
Carcinoid tumors arising in tailgut cysts may be associated with estrogen receptor status: case report and review of the literature.
Int J Clin Exp Pathol 1: 539-43



. Malignant NETs with proven metastatic capacity also displayed foci of necrosis, angioinvasion and increased Ki67 index, qualifying these NETs as G2
Click to access Pubmed
Luong TV, Salvagni S, Bordi C (2005)
Presacral carcinoid tumour. Review of the literature and report of a clinically malignant case.
Dig Liver Dis 37: 278-81




Click to access Pubmed
Song DE, Park JK, Hur B, Ro JY (2004)
Carcinoid tumor arising in a tailgut cyst of the anorectal junction with distant metastasis: a case report and review of the literature.
Arch Pathol Lab Med 128: 578-80



. Patients with sacrococcigeal NETs in general have a good prognosis, largely depending on appropriate management with either surgery or local radiation therapy, one patient being alive and well after 28 years of evolution
Click to access Pubmed
Dujardin F, Beaussart P, de Muret A, Rosset P, Waynberger E, Mulleman D, de Pinieux G (2009)
Primary neuroendocrine tumor of the sacrum: case report and review of the literature.
Skeletal Radiol 38: 819-23



. A poor outcome is reported for G2 cases
Click to access Pubmed
Liang JJ, Alrawi S, Fuller GN, Tan D (2008)
Carcinoid tumors arising in tailgut cysts may be associated with estrogen receptor status: case report and review of the literature.
Int J Clin Exp Pathol 1: 539-43




Click to access Pubmed
Luong TV, Salvagni S, Bordi C (2005)
Presacral carcinoid tumour. Review of the literature and report of a clinically malignant case.
Dig Liver Dis 37: 278-81




Click to access Pubmed
Song DE, Park JK, Hur B, Ro JY (2004)
Carcinoid tumor arising in a tailgut cyst of the anorectal junction with distant metastasis: a case report and review of the literature.
Arch Pathol Lab Med 128: 578-80




Click for details
Bosman FT, Carneiro F, Hruban RH, Theise ND (Eds.)
WHO Classification of Tumours of the Digestive System.
4th Edition
International Agency for Research on Cancer: Lyon 2010



.