11. Colorectal cancer Flashcards
What is an adenoma?
Benign but slightly-disordered growth of epithelial cells
Which type of adenoma commonly precedes colorectal cancer and what is the incidence of this type of adenoma?
Polyps
25% of adults have by 50 years
Recall the 5 categories of adenoma
Tubular Tubulovillous Villous Pedunculated (on a stalk) Sessile (rug-on-carpet)
Recall a common complication of specifically villous polyps
Can become hyper-secretory to induce a hypokalaemia
What mutation gives rise to APC
5q21
What causes microsatellite instability?
Mismatch-repair gene mutation
Give an example of a microsatellite instability disorder
HNPCC
What is the functional consequence of having a microsatellite instability?
Cannot repair faulty DNA
What sort of gene is mutated in FAP?
TSG that controls cell growth
Descirbe the nuclei of cells in tubular and villous polyps
Tubular = enlarged Villous = pseudo-stratified
About what % of cancer-related deaths are attributable to colorectal cancer?
10%
What is the main risk factor for colorectal cancer?
Poor diet
What features of diet increase colorectal cancer risk
Low fibre
High fat
Refined carbs
What features of diet can protect against colorectal cancer
Folate
Vit C and E
By what mechanism do Vit C and E protect against colorectal cancer?
Clear up free radicals
What are the 3 main presentations of colorectal cancer?
- Change in bowel habit
- PR bleeding
- Iron-deficiency anaemia
Where in the colon are colorectal tumours usually found?
Recto-sigmoid
What type of tumour are the majority of colorectal cancers?
Adenocarcinomas (originated in glandular tissue)
Recall 3 factors that may indicate high-risk screening for colorectal cancer
- Implicated gene mutation
- Crohn’s
- UC
How is population-screening for colorectal cancer carried out?
Faecal occult blood
If the screening test is positive for colorectal cancer, what additional testing is carried out?
Endoscopy - looking for polyps
WHat is the usual length of time between adenoma development and a colorectal malignancy developing?
15 years
What grading system is used for colorectal cancer?
Duke’s
Recall the grades of Duke’s that can be assigned to a colorectal cancer and what each indicates
Dukes A: neg nodes, growth limited to muscularis propria
Dukes B: neg nodes, EXTENDS beyond MP
Dukes C1: POS nodes, neg apical lymph nodes upon removal
Dukes C2: POS apical lymph nodes
What do inflammatory markers indicate about a colorectal cancer?
Good prognosis
