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.

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
  • MEN1 Syndrome
  • Neurofibromatosis type 1
  • Hereditary Non-polyposis Colorectal Cancer (HNPCC)
  • Von Hippel-Lindau disease (VHL)
  • Li-Fraumeni Syndrome

Gross Pathology

On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

Microscopic Pathology

On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

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Pathophysiology

• 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.
• The KRAS gene mutation has been associated with the development of appendix cancer.
• On gross pathology, findings of appendix cancer, include:

• 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

• On microscopic histopathological analysis findings will depend on the subtype of appendicular cancer.
• Common histopathological findings, may include:

• Cystic structures
• Angiolymphatic invasion

• The images below demonstrate different histopathological findings of appendix cancer.

• 
  Appendiceal carcinoid
• 
  Appendiceal carcinoid
• 
  Appendiceal carcinoid with necrosis
• 
  Carcinoid synaptophysin
• 
  Appendiceal tumor