W10L4 - Neoplasia of the Stomach Flashcards
Gastric Carcinoma Risk Factors and Prognosis
Risk Factors
- diffuse type - no well defined risk factor
- intestinal type - gastritis atrophic
Prognosis - invasion is most important factor
- early: limited to mucosa and submucosa; 90-95% survival at 5 years
- late: beyond submucosa; less than 10% survival at 5 years
Gastric Carcinoma - Diffuse and Intestinal Types
Diffuse (signet ring cell, linitis plastica)
- younger patients, no gender preference
- not associate with H.pylori
Intestinal
- patients greater than 50, male > female
- arises from metaplastic glands in chronic gastritis; associated with H. pylori
Growth Patterns and Spread of Gastric Carcinoma
In early gastric carcinoma the tumour is confined to the mucosa and submucosa and may exhibit a exophytic, flat or depressed or excavated conformation
Advanced gastric carcinoma extends into the muscularis propria and beyond
Linitis plastica is an extreme form of flat or depressed advanced gastric carcinoma
Linitis Plastica
Uncommonly a broad region of the gastric wall or the entire stomach is extensively infiltrated by malignancy, creating a rigid, thickened “leather bottle appearance” termed linitis plastica
It’s a morphological variant of diffuse (or infiltrating) stomach cancer
Causes of linitis plastica could be lye ingestion or metastatic infiltration of the stomach
It is not associated with H.pylori infection
This cancer (and most other stomach cancers) is more common in Asian countries
Spread of Gastric Carcinoma
Local infiltration (through wall of stomach to peritoneum, pancreas etc)
Lymphatic - local and regional lymph nodes
Blood - liver, lungs
Transcoelomic (across peritoneal cavity)
- often involves ovaries
Histology of Gastric Adenocarcinoma
Neoplastic glands are variably sized
- demonstrate mitoses, increased nuclear/cytoplasmic ratios, and hyperchromatism
In poorly differentiated gastric adenocarcinoma at high power, instead of seeing the glands, you see rows of infiltrating neoplastic cells with marked pleomorphism
- many have clear vacuole of mucin
Stain with an immunoperoxidase stain with antibody to cytokeratin as its positive in poorly differentiated neoplastic cells
- cytokeratin staining is typical for neoplasms
Histology of the Diffuse Type of Gastric Adenocarcinoma
Poorly differentiated adenocarcinomas with little or no discernible gland formation
Neoplastic cells can be seen forming a diffuse sheet infiltrating between bundle of smooth muscle
At high magnification the tumour is seen to consist of signet ring cells
- called this because the cytoplasm is occupied by a mucin-filled vacuole
Less Common Gastric Neoplasms
Lymphoma
Gastrointestinal stromal tumour (GIST)
Neuroendocrine (carcinoid) tumours
Gastric Lymphoma
2nd most common malignant tumour of the stomach
Malignant neoplasm of mucosa associated lymphoid tissue (MALT)
A (usually) low grade B-cell (marginal cell) lymphoma
Contains diffuse sheet of densely staining lymphocytes that replaces gastric mucosa
Uniformity of lymphocytes
It is a lymphoepithelial lesions
- where malignant lymphocytes infiltrate epithelium of gastric glands
GIST
Larger tumours with high mitotic rate tend to behave malignantly
Stomach is most common site
Mesenchymal neoplasms derived from interstitial cells of Cajal (pacemaker cells controlling peristalsis)
Overexpress c-kit oncogene
- used as diagnostic aid on tissue
- a target for therapy with tyrosine kinase inhibitor (imatinib)
Typically defined as tumours whose behaviour is driven by mutations in the Kit gene or PDGFRA gene, and may or may not stain positively for Kit
What is the other name for Neuroendocrine Tumours
Carcinoid tumours
Gastric Carcinoma - Clinical
90-95% of stomach malignancies
Lesser curvature of antropyloric region is most common
But an ulcerated lesion of the greater curvature is more likely to be malignant
