BOWEL CANCERS AND NEOPLASIAS

Question 1

Are colonic polyps always pre-malignant?

Answer 1

No. Most colonic polyps are metaplastic polyps with no malignant potential.

Question 2

What type of colonic polyps have malignant potential?

Answer 2

Adenomatous polyps

Question 3

How would you determine the malignant potential of a colonic adenomatous polyp?

Answer 3

The size - bigger more likely

Histological type - in decreasing order of malignant potential: villous more than tubulovillous more than tubular.

Question 4

What are the polyposis syndromes?

Answer 4

Familial adenomatous polyposis
Peutz-Jeghers syndrome
Juvenile polyposis syndrome
Cronkhite-Canada syndrome

Question 5

What is familial adenomatous polyposis?

Answer 5

Inherited autosomal dominant condition involving tumour suppressor gene APC (chromosome 5). Adenomatous polyps are found throughout the gut, especially in the colon. Colorectal cancer develops by the age of 40. Patients are offered panproctocolectomy at early stage.

Question 6

What is Peutz-Jeghers syndrome?

Answer 6

Autosomal dominant condition characterised by buccal pigmentation and development of hamartomatous polyps (juvenile polyps). Predominantly affects small intestine but found in colon too. Increased risk of cancer. Associated with mutation in gene coding serine threonine kinase.

Question 7

What is juvenile polyposis syndrome?

Answer 7

Hamartomatous polyps develop in the colon as a result of mutation on chromosome 18.

Question 8

What is Cronkhite-Canada syndrome?

Answer 8

Non-inherited condition characterised by juvenile polyps in colon. Affects middle aged adults. Associated with ectodermal abnormalities such as nail dystrophy and skin pigmentation.

Question 9

What makes a polyp adenomatous?

Answer 9

It is dysplastic

Question 10

What are the clinical features associated with colonic polyps?

Answer 10

Usually an incidental finding as part of investigation for abdominal pain, rectal bleeding or altered bowel habit.
Also, obstruction can occur
Iron deficiency anaemia if polyp bleeds
Diarrhoea seen with villous type of polyp - can cause hypokalaemia.

Question 11

What investigations should be ordered to identify colonic polyps?

Answer 11

Barium enema - may demonstrate either solitary or multiple polyps
Endoscopy and biopsy (or even removal) - most frequent method of identification

Question 12

What is likelihood of colonic polyps recurrence after their removal?

Answer 12

50%

Question 13

How do you treat colonic polyps?

Answer 13

Endoscopic removal of polyps
Surgical resection if individual polyps cannot be removed
Surveillance of patients at risk
Colonoscopic screening for those who have had a colonic adenoma

Question 14

What are the only two cancers more common than colorectal carcinoma?

Answer 14

Breast and lung

Question 15

What is the adenoma-carcinoma sequence in colorectal cancer?

Answer 15

Normal mucosa - adenomatous polyps - adenocarcinoma
As polyp becomes larger it accumulates an increasing number of genetic mutations which leads to unregulated cell growth with invasive potential and hence a cancer develops.

Question 16

Where in the colon are the majority of cancers found? Name 2 locations.

Answer 16

In the rectum (27%) and the sigmoid (20%)

Question 17

What are the risk factors for developing colorectal carcinoma?

Answer 17

Western diets of high animal fats and low fibre
Familial polyposis coli
IBD

Question 18

What are the clinical features of colorectal carcinoma?

Answer 18

Unexplained anaemia
Weight loss
Abdominal pain
Change in bowel habit
Palpable mass in right iliac fossa (caecal lesions)
Rectal bleeding (left side lesions)
Perforation and abscess formation
Jaundice - mets
Palpated tumour on rectal examination

Question 19

What investigations should be ordered for someone in whom you suspect colorectal carcinoma?

Answer 19

FBC
Faecal occult blood
Barium enema
Rigid sigmoidoscopy
Flexible sigmoidoscopy - in combination with barium enema
Colonoscopy and biopsy
Abdominal US - liver mets
CT with contrast - in those who cannot have enema or colonoscopy
MRI - resectability of tumour

Question 20

What are the common sites of metastatic spread?

Answer 20

Liver
Lungs
Bones
Peritoneal cavity

Question 21

What is the system used to stage colorectal carcinoma?

Answer 21

The Dukes staging system

Question 22

Define Dukes stage A.

Answer 22

Confined to the bowel wall. The tumour has invaded the submucosa or muscularis propria but does NOT breach the bowel wall. Lymph nodes are negative.

Question 23

Define Dukes stage B.

Answer 23

The tumour has spread through the bowel wall, ie into the mesorectal or pericolic fat. Lymph nodes are still negative.

Question 24

Define Dukes stage C1.

Answer 24

The tumour has invaded the colorectal wall and now there are positive lymph nodes. However, the apical lymph node is negative.

Question 25

Define Dukes C2

Answer 25

The tumour has invaded the bowel wall. The lymph nodes are positive including the apical lymph node.

Question 26

Define Dukes stage D.

Answer 26

This is when there is evidence of metastatic spread.

Question 27

How is someone with colorectal carcinoma treated?

Answer 27

Surgical resection

Chemotherapy +/- radiotherapy - given to patients who are Dukes B or C

Question 28

What is the overall 5 year survival rate of someone diagnosed with colorectal cancer?

Answer 28

30%

Question 29

What is the 5 year survival of someone with Dukes stage A colorectal cancer?

Answer 29

95%