11. Colorectal cancer

Question 1

What is an adenoma?

Answer 1

Benign but slightly-disordered growth of epithelial cells

Question 2

Which type of adenoma commonly precedes colorectal cancer and what is the incidence of this type of adenoma?

Answer 2

Polyps

25% of adults have by 50 years

Question 3

Recall the 5 categories of adenoma

Answer 3

Tubular
Tubulovillous
Villous
Pedunculated (on a stalk)
Sessile (rug-on-carpet)

Question 4

Recall a common complication of specifically villous polyps

Answer 4

Can become hyper-secretory to induce a hypokalaemia

Question 5

What mutation gives rise to APC

Answer 5

5q21

Question 6

What causes microsatellite instability?

Answer 6

Mismatch-repair gene mutation

Question 7

Give an example of a microsatellite instability disorder

Answer 7

HNPCC

Question 8

What is the functional consequence of having a microsatellite instability?

Answer 8

Cannot repair faulty DNA

Question 9

What sort of gene is mutated in FAP?

Answer 9

TSG that controls cell growth

Question 10

Descirbe the nuclei of cells in tubular and villous polyps

Answer 10

Tubular = enlarged
Villous = pseudo-stratified

Question 11

About what % of cancer-related deaths are attributable to colorectal cancer?

Answer 11

10%

Question 12

What is the main risk factor for colorectal cancer?

Answer 12

Poor diet

Question 13

What features of diet increase colorectal cancer risk

Answer 13

Low fibre
High fat
Refined carbs

Question 14

What features of diet can protect against colorectal cancer

Answer 14

Folate

Vit C and E

Question 15

By what mechanism do Vit C and E protect against colorectal cancer?

Answer 15

Clear up free radicals

Question 16

What are the 3 main presentations of colorectal cancer?

Answer 16

1. Change in bowel habit
2. PR bleeding
3. Iron-deficiency anaemia

Question 17

Where in the colon are colorectal tumours usually found?

Answer 17

Recto-sigmoid

Question 18

What type of tumour are the majority of colorectal cancers?

Answer 18

Adenocarcinomas (originated in glandular tissue)

Question 19

Recall 3 factors that may indicate high-risk screening for colorectal cancer

Answer 19

1. Implicated gene mutation
2. Crohn’s
3. UC

Question 20

How is population-screening for colorectal cancer carried out?

Answer 20

Faecal occult blood

Question 21

If the screening test is positive for colorectal cancer, what additional testing is carried out?

Answer 21

Endoscopy - looking for polyps

Question 22

WHat is the usual length of time between adenoma development and a colorectal malignancy developing?

Answer 22

15 years

Question 23

What grading system is used for colorectal cancer?

Answer 23

Duke’s

Question 24

Recall the grades of Duke’s that can be assigned to a colorectal cancer and what each indicates

Answer 24

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

Question 25

What do inflammatory markers indicate about a colorectal cancer?

Answer 25

Good prognosis