Editing Foregut NET

''Also known as carcinoid tumours''

''See separate topic under 'small bowel' - 'midgut NETs'''

== Epidemiology ==

* Increasing incidence in stomach - thought to be due to increasing surveillance and widespread use of PPIs

== Pathophysiology ==

* Arise from neuroendocrine precursor cells (enterochromaffin cells)
* Can manifest at any site in the body
* GIT sites:
** Stomach (8% of all NETs)
** Small intestine
** Rectum
** Appendix
* Typically non-functioning in the stomach and rarely cause carcinoid syndrome
* Classification:
** Classification based on morphology alone is not very useful, because it does not accurately predict clinical course. Need to use mitotic rate and Ki67 index. The distinction between a G3 NET and a carcinoma can be difficult.


== Classification ==

* Three distinct subtypes of gastric NETs
*

{| class="wikitable"
|
|Type 1 - complication of atrophic gastritis
|Type 2 -  complication of ZES
|Type 3 - sporadic
|Type 4 (Neuroendocrine carcinoma)
|-
|Proportion of gastric NETs
|70-80%
|5-10%
|10-15%
|
|-
|NET characteristics
|Usually non-functioning
|Usually non-functioning
|
|
|-
|Associated pathology
|ECL cells transform into NETs in setting of chronic achlorhydria and subsequent high gastrin levels.  Can occur with atrophic gastritis, pernicious anaemia, prolonged PPI use.
|ECL cells transform into NETs in setting of hypergastrinaemia, but this time it is caused by gastrinomas in pancreas or duodenum. Often seen with ZES and MEN1.
|None - sporadic tumours. Absence of atrophic gastritis, ZES or MEN1.
|
|-
|Location
|Multiple small tumours (<1cm) confined to mucosa or submucosa in fundus or body.

Tumours usually appear as polypoid lesions with a small central ulceration.
|Multiple small tumours in fundus, antrum and body
|Large solitary lesions in fundus or antrum
|
|-
|Gastric acid level
|Low
|High
|Normal
|
|-
|Serum gastrin level
|High (because of atrophic gastritis)
|High (because of ZES)
|Normal
|
|-
|Treatment
|EMR if <1-2cm


Partial gastrectomy or wedge if larger


Antrectomy sometimes performed - can lead to regression after fixing high gastrin levels.
|EMR if <1-2cm


Partial gastrectomy or wedge if larger


Treat gastrinoma
|Partial or total gastrectomy with local lymph node resection
|Aim for curative resection, but rarely possible


Palliative approaches
|-
|Prognosis
|Excellent
|Good (long-term survival 70-90%, but can metastasise to regional nodes)
|Poor (5 year survival 25-30%)
|Poor - most patients present with widespread mets. Very aggressive.
|}

== Staging ==

* See 'pancreatic NETs' topic


Staging duodenal/ampulla of Vater NENs
{| class="wikitable"
|'''Primary tumor (T)'''
|
|
|
|-
|'''T category'''
|'''T criteria'''
|
|
|-
|TX
|Primary tumor cannot be assessed
|
|
|-
|T1
|Tumor invades the mucosa or submucosa only and is ≤1 cm (duodenal tumors).

Tumor ≤1 cm and confined within the sphincter of Oddi (ampullary tumors).
|
|
|-
|T2
|Tumor invades the muscularis propria or is >1 cm (duodenal).

Tumor invades through sphincter into duodenal submucosa or muscularis propria, or is >1 cm (ampullary).
|
|
|-
|T3
|Tumor invades the pancreas or peripancreatic adipose tissue
|
|
|-
|T4
|Tumor invades the visceral peritoneum (serosa) or other organs
|
|
|-
|''NOTE:'' Multiple tumors should be designated as such (and the largest tumor should be used to assign the T category):

* If the number of tumors is known, use T(#); eg, pT3(4) N0 M0.
* If the number of tumors is unavailable or too numerous, use the m suffix, T(m); eg, pT3(m) N0 M0.
|
|
|
|-
|'''Regional lymph nodes (N)'''
|
|
|
|-
|'''N category'''
|'''N criteria'''
|
|
|-
|NX
|Regional lymph nodes cannot be assessed
|
|
|-
|N0
|No regional lymph node involvement
|
|
|-
|N1
|Regional lymph node involvement
|
|
|-
|'''Distant metastasis (M)'''
|
|
|
|-
|'''M category'''
|'''M criteria'''
|
|
|-
|M0
|No distant metastasis
|
|
|-
|M1
|Distant metastases
|
|
|-
|M1a
|Metastasis confined to liver
|
|
|-
|M1b
|Metastases in at least one extrahepatic site (eg, lung, ovary, nonregional lymph node, peritoneum, bone)
|
|
|-
|M1c
|Both hepatic and extrahepatic metastases
|
|
|-
|'''Prognostic stage groups'''
|
|
|
|-
|'''When T is...'''
|'''And N is...'''
|'''And M is...'''
|'''Then the stage group is...'''
|-
|T1
|N0
|M0
|I
|-
|T2
|N0
|M0
|II
|-
|T3
|N0
|M0
|II
|-
|T4
|N0
|M0
|III
|-
|Any T
|N1
|M0
|III
|-
|Any T
|Any N
|M1
|IV
|}


== Workup ==

* Gastroscopy
** EUS can help establish depth of lesion
* CT
** Bright enhancement on CT on arterial phase, mets will also be hyperenhancing
* PET
** Avid on DOTATATE-PET or octreotide scan
* Chromogranin A is often elevated - useful as biomarker



[[Category:UGIS]]