Pathology of Colorectal Cancer

Question 1

What is a polyp?

Answer 1

A protrusion above an epithelial surface.

Question 2

What are the 2 types of malignant epithelial polyp?

Answer 2

Polypoid adenocarcinomas and carcinoid polyps.

Question 3

What are the 4 differential diagnoses of a polyp?

Answer 3

1. Adenoma. 2. Serrated polyp. 3. Polypoid carcinoma. 4. Other.

Question 4

How can you tell polyps apart?

Answer 4

Histopathology.

Question 5

What are the 3 macroscopic appearances of polyps?

Answer 5

Pedunculated (hang on a stalk), flat, sessile (slightly raised, look like seaweed).

Question 6

What layers of the colon do polyps contain?

Answer 6

Mucosa and submucosa.

Question 7

What is the histology of an adenoma in a polyp?

Answer 7

Crypts full of usually clonal epithelial cells.

Question 8

What are the 3 microscopic arrangements of colonic adenomas?

Answer 8

Tubullovillous (have tubes and villi), tubular (have tubes), villous (have villi).

Question 9

What are the common mutations in the formation of an adenoma and an adenocarcinoma?

Answer 9

APC mutation, K-ras mutation, p53 mutation.

Question 10

Should all adenomas be removed if they can be?

Answer 10

Yes as they are all premalignant.

Question 11

Does this molecule pathway occur with all colorectal adenomas?

Answer 11

No, there are separate pathways for inherited tumours and serrated adenomas.

Question 12

What do almost all adenocarcinomas produce?

Answer 12

Glands.

Question 13

What surrounds the glands in adenocarcinomas?

Answer 13

Dense desmoplastic stoma (fibrous tissue).

Question 14

Describe Duke’s staging A, B and C.

Answer 14

A - confined by muscularis propria.
B - through muscularis propria.
C - metastatic to lymph nodes.

Question 15

What percentage of colorectal cancers are left and right sided?

Answer 15

75% left sided (rectum, sigmoid, descending), 25% right sided (caecum, ascending).

Question 16

What are the presenting complaints for left sided cancers?

Answer 16

Blood PR, altered bowel habit, obstruction.

Question 17

What are the presenting complaints for right sided cancers?

Answer 17

Anaemia, weight loss.

Question 18

For adenocarcinomas, what kind of gross appearance can they have?

Answer 18

Polypoid, structuring, ulcerating.

Question 19

Does the histological appearance of adenocarcinomas differ?

Answer 19

No.

Question 20

When is the usual haematogenous spread of colorectal cancer?

Answer 20

Liver (due to portal venous system).

Question 21

What are the 2 inherited colorectal cancer syndromes?

Answer 21

Hereditary non-polyposis coli (HNPCC, Lynch syndrome), familial adenomatous polyposis (familial polyposis coli).

Question 22

How does the onset of HNPCC and FAP differ?

Answer 22

HNPCC: late onset. FAP: early onset.

Question 23

What gene mutations and types of gene mutations causes HNPCC?

Answer 23

DNA mismatch repair proteins. Mutation in MLH-1, MSH-2, PMS-1 or MSH-6 genes.

Question 24

Are HNPCC and FAP autosomal dominant or recessive?

Answer 24

Dominant.

Question 25

What gene mutations and type of gene mutations causes FAP?

Answer 25

Tumour suppression, in the FAP gene.

Question 26

Where do HNPCC and FAP cause tumours?

Answer 26

HNPCC - right sided tumours.

FAP - throughout colon.

Question 27

How many polyps does HNPCC and FAP have?

Answer 27

HNPCC: <100.
FAP: >100.

Question 28

Which of HNPCC and FAP causes a Crohn’s like inflammatory response?

Answer 28

HNPCC.

Question 29

What tumours is FAP associated with?

Answer 29

Desmoid tumour (arises from connective tissue) and thyroid carcinoma.

Question 30

What tumours is HNPCC associated with?

Answer 30

Gastric and endometrial carcinoma (usually gets prophylactic historectomy).