15.5 Pathology: Dysplasia carcinoma sequence in colorectal cancer

Question 1

What type of lesion is an adenomatous polyp?

Answer 1

Premalignant lesion

Question 2

What are key features that predict increased malignancy risk?

Answer 2

Polyp size (>1cm)
Villous morphology
High grade dysplasia

Question 3

What kind of condition is familial adenomatous polyposis?

How is it defined?

Answer 3

Autosomal dominant condition

Defined as >100 adenomatous polyps in large bowel

Question 4

What is the difference between an adenomatous polyp and a malignant lesion?

Answer 4

No invasion beyond muscularis mucosae

Question 5

What is a common early event in adenoma formation?

Answer 5

APC mutation

Question 6

What is a common proto-oncogene mutation?

Answer 6

K-RAS or B-RAF

Question 7

What is the most common familial colorectal cancer syndrome?

Answer 7

Lynch syndrome (autosomal dominant, early onset colorectal cancer, one ‘hit’ in tumour supressor genes

Question 8

For colorectal staging using the TMN system, what are the 4 categories of T severeity?

Answer 8

T1: Beyond MM
T2: Into MP
T3: Beyond MP
T4: Invades other organs/structures or perforates visceral peritoneum

Question 9

How many hits do:
oncogenes
tumour supressor genes

Need to be altered?

Answer 9

Oncogenes: activating mutations (1 hit)

Tumour supressor genes: inactivating (2 hits)

Question 10

Which syndromes involve microsatellite instability?

Which involves chromosomal instability?

Answer 10

HNPCC/Lynch Syndrome

FAP

Question 11

What do we see in a dysplastic lesion?

Answer 11

Nuclear atypia

Disordered growth

Question 12

What indicates metastatic potential?

Answer 12

Barrier breach, desmoplasia

complete excision of dysplasia is curative