Cancer: Colorectal cancer

Question 1

How common is colon cancer worldwide?

Answer 1

4th most common cancer overall

Question 2

What rank is colon cancer as the cause of death in cancers?

Answer 2

2nd (behind lung cancer)

Question 3

Describe two features of a normal large bowel

Answer 3

Mucosa is folded but smooth

There is a thick muscle layer (muscularis)

Question 4

How many cells die per minute in the colon?

Answer 4

2-5 million

Question 5

What does the APC gene do?

Answer 5

Adenoamtous polyposis coli gene product reduces risk of mutation during replication

Question 6

Name three protective mechanisms to eliminate genetically defective cells

Answer 6

Natural cell loss
DNA monitors
Repair enzymes

Question 7

Define a polyp

Answer 7

Any projection from a mucosal surface into a hollow viscus, and may be hyperplastic, neoplastic, inflammatory, hamartomatous etc.

Question 8

Define an adenoma

Answer 8

Benign neoplasm of the mucosal epithelial cells (or more generally just glandular cells in epithelial tissue)

Question 9

Describe features of hyperplastic polyps, and their prevalence

Answer 9

They are very common, making up 90% of all colonic polyps

There are often multiple polyps

They have NO MALIGNANT POTENTIAL

15% have K-Ras mutations

Question 10

Name the three colonic adenoma types

Answer 10

Tubular (75% tubular) - common

Tubulovillous (25-50% villous) - rare

Villous (>50% villous) - very rare

Question 11

If an adenoma is villous is this better or worse for the prognosis?

Answer 11

Worse

Question 12

Name the shapes of adenomas

Answer 12

Pedunculated

Sessile

Question 13

Describe pedunculated adenomas

Answer 13

On a stalk, look a bit like a tree

Question 14

Describe sessile adenomas

Answer 14

Flat and raised, like a thick plush rug

Question 15

Describe the microscopic structures of tubular adenomas

Answer 15

Columnar cells with nuclear enlargement, elongation, multi-layering and loss of polarity

Increased proliferative activity

Reduced differentiation

Complexity/disorganisation of architecture

Question 16

Describe the microscopic structure of villous adenomas

Answer 16

Mucinous cells with nuclear enlargement, elongation, multi-layering and loss of polarity

Exophytic - growing outwards

Rarely may have hyper-secretory function and result in excess mucus discharge and hypokalaemia

Question 17

Define dysplasia

Answer 17

Abnormal growth of cells with some features of cancer

Can be low and high grade

Question 18

Name the most famous condition that increases the number of polyps

Answer 18

FAP (familial adenomatous polyposis)

5q21 gene mutation