13: Colorectal Cancer

Question 1

Difference between polyp and adenoma?

Answer 1

Polyp = Any projection from mucosal surface into a hollow viscus, may be hyperplastic/neoplastic/inflammatory etc..

Adenoma = benign neoplasm of mucosal epithelial cells

Question 2

What are hyperplastic polyps?

Answer 2

Very common, 90% of all large intestine polyps
No malignant potential
Often multiple

Question 3

Colonic adenoma types

Answer 3

Tubular (most common)
Tubulovillous
Villous

Pedunculated
Sessile

Question 4

Structure of tubular adenomas

Answer 4

Columnar cells
Nuclear enlargement
Elongation, multi-layering, loss of polarity
Increased proliferative activity
Reduced differentiation
Disorganised architecture

Question 5

Structure of villous adenomas

Answer 5

Mucinous cells

Finger-like extensions

Question 6

What condition increases risk of dysplasia?

Answer 6

Ulceritive Colitis - due to ongoing inflammation

Question 7

What condition increases risk of dysplasia?

Answer 7

Ulceritive Colitis - due to ongoing inflammation

Question 8

Pathology of Adenomatous Polyposis Coli (APC)

Answer 8

5q21 mutation

Question 9

What is the principle of adenoma-carcinoma sequence?

Answer 9

Gradual accumulation of genetic abnormalities eventually progressing from adenoma to carcinoma

Question 10

Genetic pathways for cancer?

Answer 10

Adenoma-carcinoma sequence (develop adenoma FIRST)
APC gene, K-ras, p53

Microsatellite instability:
Involved in gene repair
Repeat sequences prone to misalignment

Question 11

2 main genetic pathways

Answer 11

FAP - Inactivation of APC tumour suppressor genes

HNPCC - microsatellite instability

Question 12

Colonic carcinoma epidemiology

Answer 12

35000 per year in UK
10% of cancer deaths
Mostly age 50-80
Diet factors: High fat/red meat, low fibre

Question 13

Clinical presentation

Answer 13

Change in bowel habit
Bleeding PR (rectal)
Unexplained iron deficiency anaemia

Question 14

Macroscopic features?

Answer 14

Small carcinomas may be present WITHIN larger polypoid adenomas

Question 15

Most common place where CRC occurs?

Answer 15

Rectosigmoid (most common)

Question 16

What kind of tumours do you get?

Answer 16

Adenocarcinomas (glandular epithelial tissue)

Other rare:
Neuroendocrine
Mucinous carcinomas

Question 17

How are they graded?

Answer 17

Well differentiated
Moderately differentiated (most common)
Poorly differentiated

Question 18

What is Duke’s classification?

Answer 18

Dukes A = limited to wall (nodes negative)
Dukes B = growth beyond muscularis propria
Dukes C1 = nodes POSITIVE, apical node negative
Dukes C2 = apical node positive

If lymph nodes affected at all, graded C

Question 19

Types of screening?

Answer 19

High risk screening

• Previous adenoma
• UC or Crohn’s disease
• Hereditary traits

Population screening

Question 20

How is screening done for CRC?

Answer 20

Fecal occult blood (FOB)
Assess stool for blood
If there is:
55-60 = sigmoidoscopy 
60-75 (older) = colonoscopy