Colorectal Polyps and Cancer

Question 1

What are colorectal polyps?

Answer 1

A small overgrowth of epithelial cells which form along the lining of the colon or rectum

=> Can be benign or malignant

Question 2

What are the risk factors of Colorectal Polyps?

Answer 2

• Increased cell divisions
• Genetic conditions
• Smoking
• IBD (UC)
• Age (old age)

Question 3

What are the 3 different types of polyps?

Answer 3

• Adenomatous
• Serrated
• Harmatomatous

Question 4

What is the cause of adenomatous polyps?

Answer 4

• Mutation in the Adenomatous Polyposis Coli (APC) gene on chromosome 5
• APC gene is a type of tumour supressor gene

Question 5

What is Familial Adenomatous Polyps Syndrome?

Answer 5

• Mutation of APC gene since birth
• Colon and rectum full of polyps
• Colon must be removed as there is greater chance that one of the many polyps may turn malignant (prophylactic panproctocolectomy)

=> Rare and less common than HNPCC

=> Order of prevalance of Colorectal Cancer causes:

• Sporadic
• HNPCC
• FAP

Question 6

What are the 3 different types of Adenomatous Polyps?

Answer 6

• Tubular
• Villous
• Tubulovillous

=> These polyps may have peduncated (long) or sessile (broad) stalks

=> Villous, sessile adenomatous polyps are more likely to become malignant

Question 7

What is the characteristic appearance of a serrated polyp?

Answer 7

Saw tooth like appearance

Question 8

What is the main cause of serrated polyps formation?

Answer 8

Methylation of promotor region

Question 9

What are the 2 types of serrated polyps?

Answer 9

=> Small polyps - also known as hyperplastic polyps

=> Large polyps - flat and sessile, greater tendency to become malignant

Question 10

What are the clinical features of colorectal polyps?

Answer 10

• Rectal bleeding
• Anaemia
• Abdominal pain
• Constipation
• Mucus discharge
• Prolapse out of anus

=> symptoms only occur when polyps increase in size and proximity to the anus

Question 11

What is the differential diagnosis of rectal bleeding?

Answer 11

• Mesenteric ischaemia
• Small bowel ulceration
• Small bowel diverticulosis
• Meckel diverticulum
• Colonic/rectal varicies
• GI Bleeding in runners
• Endometriosis

Question 12

What is the differential diagnosis of constipation?

Answer 12

• Abdominal hernias
• Anxiety disorders
• Appendicitis
• Colon cancer
• Colonic obstruction
• Depression
• IBS
• Intestinal motility disorders

Question 13

What type of carcinomas are colorectal carcinomas?

Answer 13

Adenocarcinomas - originating from cells lining the colonic crypts

Question 14

What are the different pathways of tumorigenesis of Colorectal Carcinomas?

Answer 14

=> Chromosomal Instability Pathway (Adenoma carcinoma pathway)

=> Microsatilite Instability Pathway (Serrated Pathway):

• Serrated polyps acquire sporadic mutations in BRAF of mismatch repair genes
• Or through microsatilite instability

Question 15

What are the risk factors of colorectal carcinoma?

Answer 15

=> Non-modifiable:

• Age (being elderly)
• Gender (being male)
• IBD

=> Modifiable:

• Smoking
• Lack of fibre in diet
• Red meat
• Obesity

Question 16

What are the clinical features of Colorectal cancer?

Answer 16

• Pain and weight loss (if carcinoma is ascending colon)
• Rectal bleeding
• Abdominal pain
• Blood streaked stools

Question 17

What is Heriditiary Non Polyposis Colorectal Cancer?

Answer 17

• Autosomal Dominant condition

- Caused of defective DNA mismatch repair

Question 18

What are the different stages of Colorectal Cancer?

Answer 18

=> Stage 0
- Not passed mucosa

=> Stage 1

• Beyond mucosa
• No lymph nodes

=> Stage 2

• Entire wall breached
• No lymph nodes

=> Stage 3

• Lymph nodes
• No distant organs

=> Stage 4

• Metastatic
• Has reached distant organs

Question 19

What is the screening and management of Colorectal Cancer?

Answer 19

• Early detection via routine colonoscopy for people with relatives that have colorectal cancer
• Faecal Immunochemical Test is a screening programme arranged once every 2 years for men ages 60-74 in England and 50-74 in Scotland
• Cancer confined to wall are surgically removed
• Chemotherapy if lymph nodes involved
• Incurable if metastatic

Question 20

What extra-colonic cancer is commonly associated with Hereditary Non Polypoisis Colorectal Cancer?

Answer 20

Endometrial Cancer

Question 21

What tumour marker is used to monitor the recurrence of cancer post operatively in cases of Colorectal Cancer?

Answer 21

Carcinoembryonic antigen

Question 22

What is the most common type of inherited Colorectal Cancer?

Answer 22

Hereditary Non Polyposis Colorectal Carcinoma - germline mutations in mismatch repair genes inherited in an autosomal dominant fasion\

Question 23

What are the referral guidelines concerning Colorectal Cancer?

Answer 23

Patients ≥ 40 with unexplained weight loss or abdominal pain

Patients ≥ 50 with unexplained rectal bleeding

Patients ≥ 60 with iron deficiency anaemia or a change in bowel habit

Question 24

What are the important prognostic factors of colorectal Cancer?

Answer 24

• Stage
• Grade
• Extramural vascular invasion
• Completeness of surgical excision

Question 25

What are some of the procedures involved in colorectal Cancer treatment?

Answer 25

• Prophylactic Panproctocolectomy (in cases of FAP as adenocarcinoma very likely to manifest)
• Anterior resection for colorectal cancers in the rectum
• Hartmann’s for left sided colon cancer, or perforated or obstructed diverticular disease

=> Hartmann’s is an emergency procedure involving the removal of sigmoid colon and part of rectum.