T1 L13: Bowel cancer - pathology and screening process Flashcards
What are the risk factors of bowel cancer?
Red meat, fat, Longstanding ulcerative colitis, crohns disease, presence of adenoma in the large bowel, FM of bowel cancer, old age
What foods reduce the risk of bowel cancer?
Veg, fruit, and fibre
What things lower the risk of bowel cancer?
Physical activity, low BMI, healthy diet
How does a high fibre diet reduce your risk of bowel cancer? (3 reasons)
- It increases the formation of short chain fatty-acids which promote health of gut microorganisms and reduces the proliferation of neoplastic cells
- It decreases the transmit time of the stool so the possible carcinogens have less interaction with the bowl mucosa
- fibre reduces the formation of secondary bile acids which can be carcinogenic
What is a polyp?
A protruding growth into a hollow viscus
What is an adenoma?
A non-cancerous tumour
What does hyperplastic mean?
A growth like a polyp that rarely turn into cancer
What is the difference in appearance between between villous and tubular adenoma?
Tubular looks like tubes, villous looks like fingers. Tubularvillous has a mixture of both
What is the adonoma-carcinoma sequence?
The progression of normal mucosa to adenoma or cancer
What is familial adenomatous polypsis?
When someone has hundreds of dysplastic polyps in their large intestine.
What is the minimum of polyps in the large intestine needed to make a diagnosis of familial adenomatous polyposis (FAP)?
100
What is the prophylactic treatment for familial adenomatous polyposis (FAP)?
Colectomy at around the age of 20
What is the genetic reason for familial adenomatous polyposis (FAP)?
A hereditary autosomal dominant condition on chromosome 21 ( APC gene (adenomatous polyposis coli))
Explain the role of a first and second hit in the development of familial adenomatous polyposis (FAP)
1st hit - The 1st abnormal gene is acquired in utero
2nd hit - The seconds genetic abnormality in somatic cells that paves the way for the development of polyps
What is p53?
A tumour suppressor gene that causes most cancers
What is Lynch syndrome?
A hereditary non-polyposis colorectal cancer
What is attenuated familial adenomatous polyposis (FAP)?
Less than 100 adenomas in the colon
What is familial colorectal cancer type X?
A bowel cancer that doesn’t that doesn’t spread
What part of the colon does Lynch syndrome usually affect?
The caecum and right colon, before the age of 50
What is the genetic cause of Lynch syndrome?
Caused by a base par mismatch (Thymine instead of Cytosine)
What are microsatallites?
Bits of repetitive DNA
What are the MSH2, MLH1, PMS1, and PMS2 gene tests used to diagnose?
Lynch syndrome
What are the Amsterdam criteria for Lynch syndrome?
- Three or more relatives with LS-associated cancer, one needs to be a first degree relative
- relatives diagnosed before 50
- FAP is excluded
- tumours are verified
What are the symptoms of bowel cancer?
Can be asymptomatic. Change in bowel habit, bleeding, anaemia, abdominal pain
What is meant by change in bowel habit?
Constipation alternating with diarrhoea due to obstructive cancer
What is the mechanism for the development of spurious diarrhoea?
Stool accumulates above a stricture and due to bacterial fermentation, the stool liquifies and rushes though the stricture
How do you diagnose bowel cancer?
Flexible sigmoidoscopy and colonoscopy with biopsy and a histological examination. MRI is then done to assess local spread
How is cancer staged?
TNM system (tumour, node metastasis, and metastasis)
What is the appearance of a T1 staging of bowel cancer?
Invasion of the submucosa but the muscularis propria is clear
What is the appearance of a T2 staging of bowel cancer?
The muscularis propria is involved without a full thickness invasion (only the inner layer is invaded)
What is the appearance of a T3 staging of bowel cancer?
A full thickness invasion but not the serosa
What is the appearance of a T4 staging of bowel cancer?
A full thickness invasion including the serosa
What is faecal immunochemical testing (FIT)?
Testing for occult blood in the faeces using an antibody specific for human blood
What other diseases other than bowel cancer could cause a positive Faecal immunochemical test (FIT) test?
Haemorrhoids and inflammation
