Bowel cancer - Pathology and the screening process Flashcards
Where does bowel cancer have a high incidence?
High incidence in western world; low incidence in Asia and Central Africa
Bowel cancer affects men and women equally
Risk factors for bowel cancer
- Migration from a low risk population to a high risk population
- Foods rich in red meat and fat increase risk of bowel cancer
- Longstanding ulcerative colitis
- Crohn’s disease - to a lesser extent than UC
- Presence of adenoma in the large bowel
- Previous history of bowel cancer surgery
- Family history of bowel cancer
- Old age
What factors reduce the risk of bowel cancer?
Physical activity and low BMI are associated with low risk of cancer
Foods rich in veg, fruit and fibre
How do foods rich in veg, fruit and fibre reduce the risk of bowel cancer?
Increase in faecal bulk and reduces transit time
How does high fibre diet reduce bowel cancer?
- Increases formation of short chain fatty acids which promote healthy gut microbes which induce differentiation, arrest growth of cells and cause apoptosis
- By increasing stool bulk, thereby reducing stool transit time –> potential carcinogens in the stool have a shorter contact with the bowel mucosa
- By reducing secondary bile acid formation which are potentially carcinogenic
What is a polyp?
Polyp is a protrusion into a hollow viscus, can be benign adenoma or malignant
What is an adenoma?
Pre-cancerous lesions
What type of epithelium do adenomas consist of?
Dysplastic epithelium
What type of feature is low grade dysplasia?
Early precancerous feature
What type of feature is high grade dysplasia?
Advanced precancerous feature, high risk of invasion if not removed
What are pathological features of polyps?
Hyperplastic, tubular adenoma, villous adenoma, tubulovillous adenoma
What is hyerplasia in polyps?
More goblet cells than normal mucosa; has a lace-like pattern
What is familial adenomatus polyposis?
- Hundreds to thousands of polyps in large bowel, 500-2500
- Minimum of 100 polyps required to make diagnosis of FAP
Why are the polyps called adenomas?
Polyps are dysplastic
Where does FAP increase the risk of cancer?
Duodenum