Colorectal Cancer

Question 1

Where is the Apc gene located

Answer 1

Chromosome 5q21

Question 2

What genes are mutated and are said to lead to an increased risk of colorectal cancer

Answer 2

Apc, kras p53

Apc gene which is a tumor suppressor gene and leads to mutations in kras gene which causes formation of polyps which leads to mutations in p53 gene which increases expression of cox that aids in carcinoma formation

Nb aspirin reduce incidence of cancer as it works against cox pathway

Question 3

What is the relationship between polyp size and risk of developing malignancy

Answer 3

<1cm size polyp: 1% risk of malignancy
1-2cm: 10% risk
>2cm: 50% risk

Question 4

What are the two neoplastic/ pre malignant polyps

Answer 4

Hamartomatous vs Adenomatous

Hamartomatous may be of large bowel( juvenile polyps) or of small bowel(peutz jeghers syndrome).. ass as well with hyperpigmentation of lips and by cal mucosa

Adenomatous may be villous, tubulovillous and tubular… villous has 40% malignancy risk, then 20 for tubulovillous and 5 tubular