GI - Colorectal Carcinoma

Question 1

Epidemiology

Answer 1

• 3rd commonest cancer
• 2nd commonest cause of cancer deaths
• Age: peak in 60s, rectal cancer more common in men

Question 2

Colonic adenomas

• What?
• Classification

Answer 2

-Benign precursors to CRC, characterised by dysplastic epithelium
-Classification:
A) Tubular: small, pedunculated, tubular glands
B) Villous: large, sessile (flat), covered by villi
C) Tubulovillous: mixture

Question 3

Colonic adenomas

• Presentation
• What features increase malignant potential?

Answer 3

• Presentation: typically asymptomatic, large polyps can bleed and villous adenomas can lead to hypokalaemia + hypoproteinaemia
• Malignant potential: increases in size, dysplasia and villous component

Question 4

Describe the adenoma to carcinoma sequence

Answer 4

• First hit: mutation in one APC copy
• Second hit: mutation in second APC copy —> leads to adenoma formation
• Additional mutations in adenoma: malignant transformation (eg KRAS, p53)

Question 5

Other aetiological factors which contribute to development of colorectal carcinoma

Answer 5

• Diet: low in fibre and high in carbs
• IBD: 15% associated with pancolitis for 20 years (they get regular colonoscopic surveillance b/c of this)
• Familial: FAP, HNPCC, Peutz-Jeghers
• Smoking
• Genetics: no relative is 1/50 CRC risk vs one 1st degree is 1/10
• *NSAIDS/aspirin 300mg/day is protective

Question 6

Pathology: what types of malignancy is it?

Answer 6

• 95% are adenocarcinomas

- Others: lymphoma, GIST and carcinoid

Question 7

Locations

Answer 7

• Rectum: 35%
• Sigmoid: 25%
• Caecum and ascending colon: 20%
• Transverse: 10%
• Descending: 5%
• Proximal tumours: sessile or polyploid
• Distal tumours: annular and stenosis

Question 8

Possible locations of spread

Answer 8

• Local
• lymphatic
• blood: liver and lungs
• transcoelomic

Question 9

Presentation: left sided

Answer 9

• Altered bowel habit (main factor)
• PR mass (60%)
• Obstruction (25%)
• PR: bleeding or mucus
• tenesmus

Question 10

Presentation: right sided

Answer 10

• Anaemia (main trait)
• wt loss
• abdo pain

Question 11

Presentation: present in either

Answer 11

• Abdo mass
• perforation
• haemorrhage
• fistula

Question 12

Examination: notable findings/things to look out for

Answer 12

• Palpable mass: per abdo or PR
• Perianal fistulae
• Hepatomegaly
• Anaemia
• Signs of obstruction