Editing Appendiceal neoplasms (section)

== '''Appendiceal neuroendocrine neoplasms''' (ANENs - formerly known as carcinoid tumour) ==

* Epidemiology
** Most common appendiceal neoplasm (65%)
** Seen in 3-5/1000 appendicectomies
** Most commonly diagnosed 10-30yo
* Pathophysiology
** Most originate from serotonin-producing enterochromaffin cells
** More benign that other NETs. Prevalent at autopsy. May even undergo spontaneous involution. Overall met rate is 3.8%.
** Can actually cause appendicitis - think about this if tip appendicitis is present
** Typically small, well-circumscribed lesions within the distal appendix
** Variable biological behaviour depending on grade
*** G1 - well-differentiated
*** G2 - intermediately-differentiated
*** G3 - poorly-differentiated neuroendocrine carcinoma
*** Mixed neuroendocrine carcinomas
** Size is the best initial predictor of malignant behaviour and metastatic potential - so base initial management on size and location
* Staging

'''Neuroendocrine tumors of the appendix TNM staging AJCC version 9'''
{| class="wikitable"
|'''Primary tumor (T)*'''
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|'''T category'''
|'''T criteria'''
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|TX
|Primary tumor cannot be assessed
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|T0
|No evidence of primary tumor
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|T1
|Tumor ≤2 cm in greatest dimension
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|T2
|Tumor >2 cm but ≤4 cm in greatest dimension
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|T3
|Tumor >4 cm in greatest dimension, or with subserosal invasion, or involvement of the mesoappendix
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|T4
|Tumor perforates the peritoneum, or directly invades other adjacent organs or structures (excluding direct mural extension to adjacent subserosa of adjacent bowel), eg, abdominal wall and skeletal muscle
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|''NOTE:'' Multiple tumors should be designated as such (the largest tumor should be used to assign T category):

* Use T(#); eg, pT3(4) N0 M0, or
* Use the ''m'' suffix, T(m); eg, pT3(m) N0 M0

'''Primary tumor suffix'''

* (m) Multiple synchronous primary tumors
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|'''Regional lymph nodes (N)*'''
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|'''N category'''
|'''N criteria'''
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|NX
|Regional lymph nodes cannot be assessed
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|N0
|No tumor involvement of regional lymph node(s)
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|N1
|Tumor involvement of regional lymph node(s)
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|'''Regional lymph nodes suffix'''

* (f) FNA or core needle biopsy
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|'''Distant metastasis (M)*'''
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|'''M category'''
|'''M criteria'''
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|cM0
|No distant metastasis
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|cM1
|Distant metastasis
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|cM1a
|Metastasis confined to liver
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|cM1b
|Metastases in at least one extrahepatic site (eg, lung, ovary, nonregional lymph node, peritoneum, bone)
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|cM1c
|Both hepatic and extrahepatic metastases
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|pM1
|Microscopic confirmation of distant metastasis
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|pM1a
|Microscopic confirmation of metastasis confined to liver
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|pM1b
|Microscopic confirmation of metastases in at least one extrahepatic site (eg, lung, ovary, nonregional lymph node, peritoneum, bone)
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|pM1c
|Microscopic confirmation of both hepatic and extrahepatic metastases
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|AJCC prognostic stage group is assigned based on the stage classification and categories chosen.*
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|'''Prognostic stage groups'''
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|'''When T is...'''
|'''And N is...'''
|'''And M is...'''
|'''Then the stage group is...'''
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|T1
|NX, N0
|M0
|I
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|T2
|NX, N0
|M0
|II
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|T3
|N0
|M0
|II
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|T4
|N0
|M0
|III
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|Any T
|N1
|M0
|III
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|Any T
|Any N
|M1
|IV
|}

* Management
** Treatment based on size:
*** <1cm - mostly benign - treated by appendicectomy and excision of mesoappendix
*** 1-2cm - base decision for right hemicolectomy on histologic factors (Ki-67 index >3%, G2 or higher, lymphovascular or perineural invasion)
*** >2cm - treated more aggressively with right hemicolectomy and regional lymphadenectomy
** Indications for right hemicolectomy if found incidentally on histology:
*** >2cm in diameter
*** Positive or unclear margins
*** Deep meso-appendiceal invasion (>3mm)
*** High proliferation rate (WHO grade 2)
*** Angio-invasion
* Surveillance
** Chromogranin-A is a good tumour marker
* Prognosis
** Local: 95-100% at 5 year survival
** Regional: 85-100% survival at 5 years
** Metastatic: 34% five year survival