Appendix cancer pathophysiology

	Appendix cancer Microchapters
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Soroush Seifirad, M.D.[2]

Overview

The pathophysiology of appendix cancer depends on the histological subtype. There are two major subtypes of appendix cancer, adenocarcinomae and carcionid tumors. While carcinoid tumors arises from enterochromaffin cells (Kulchitsky cells), which are secretory cells that are normally involved in neuroendocrine hormonal secretions, adenocarcinomae are the result of mutations in mucous producing epithelial cells. Their physiology, pathophysiology, genetic pathways, prognosis as well as epidemiology are different and hence discussed separately. The progression to adenocarcinoma usually involves the KRAS, APC, TP53, and RAF pathways, While β-catenin, NF1, and MEN1 genes are major contributors of carcinoid tumor s progression.

Pathophysiology

Physiology

The normal physiology of entrochromaffin cells is secretion of serotonin (5-HT), histamine, kallikrein, prostaglandins, and tachykinins.

Glandular epithelial cells are responsible for mucous production.

Pathogenesis

The pathophysiology of appendix cancer depends on the histological subtype.
Adenocarcinoma arises from epithelial glandular cells, which are normally involved in mucous production.
Carcinoid tumors arise from entrochromaffin cell, which are neuroendocrine cells that are normally involved in secretion of serotonin (5-HT), histamine, kallikrein, prostaglandins, and tachykinins.
The pathogenesis of appendix cancer is characterized by an initial epithelial dysplasia, followed by the formation of cystic structures and angiolymphatic invasion. Subsequently, in the advanced stages of appendix cancer, tumor cells detach from the primary tumor mass and gain access to the peritoneal cavity.^[1]

Genetics

Genes involved in the pathogenesis of carcinoid tumors of appendix include:

β-catenin,
NF1,
MEN1

The development of appendiceal adeocarcinoma is the result of multiple genetic mutations such as:

KRAS
APC
TP53
RAF

Associated Conditions

Conditions associated with appendiceal cancers include:

Chronic inflammatory disease such as Ulcerative colitis
Familial cancer syndromes

Gross Pathology

On gross pathology, findings of appendix cancer, include:^[1]

Well-demarcated mass
Average size between 1 and 5 cm
Gray or yellowish color
Deformed appendix

The image below demonstrates gross pathology of appendix cancer.

Gross pathology appendix cancer

Microscopic Pathology

On microscopic histopathological analysis findings will depend on the subtype of appendicular cancer.
Common histopathological findings, may include:^[1]