Colorectal Cancer

Question 1

What are some macropscopic descriptions of colon cancers

Answer 1

Villus, Tubal or Tubovillus

Question 2

What is lynch Syndrome of Hereditory nonpolyposis colorectal cancer

Answer 2

Is the development of colorectal cancer (2-3%) that is predispososed by the presence of microsatellite instability in the genes MSH3 and MLH1 which are mismatch repair genes. Is an autosomal dominant conditions. Typically presents as a Sessile serrated adenoma; mucinous adenocarcinoma this develops on the right side (ascending)

Question 3

What is Familial Adenomatous Polyposis

Answer 3

Is an inherited colorectal cancer syndrome (1%) in which the tumour suppressor gene APC is lost. Is an autosomal dominant condition

Question 4

What are some of the histological appearances of FAP

Answer 4

• Abnormal Crypt hyperplasia
• Goblet cell depletion
• Abnormal glandular tissue
• increased mitotic count
• No invasion past the musculosa muscularis

Question 5

What structure must the cancer invade past to become malignant

Answer 5

When the dysplastic growth passes through the musculosa muscularis it is a malignant adenocarcinoma with associated desmoplasia

Question 6

What is the typical dysplasia sequence in colorectal cancer

Answer 6

• Inherited APC loss
• Second hit hypothesis of TS APC
• Dysplastic abberrant crypt foci
• Early adenoma
• intermediate adenoma
• Late adenoma
• Adenocarcinoma
• Metastasis

Question 7

What are the other genes that must be lost in order to promote the dysplastic sequence

Answer 7

p53, k-ras, b-catenin and SMAD-4.

Question 8

What are the different staging systems for the T of TNM

Answer 8

T0- no invasion, dyplasia
T1- invades MM
T2 – Invade MP
T3 – Invades the subserosa
T4 - invades the organs

Question 9

What are the different staging systems for the N of TNM

Answer 9

N0 – no lymph node
N1- one to 3 lymph nodes
N2 – 4 or more lymph nodes

Question 10

What gene is lost when a colorectal cancer progresses from an early adenoma to intermediate adenoma

Answer 10

K-Ras

Question 11

What gene is lost when a colorectal cancer progresses from an intermediate adenoma to a late adenoma

Answer 11

Smad-2/4 regulators of TGF-b

Question 12

What gene is lost when a colorectal cancer progresses from a late adenoma to a carcinoma

Answer 12

p53

Question 13

What gene is lost when a colorectal cancer progresses from normal normal epithelium to a dysplastic ACF

Answer 13

Beat-catenin which can control the regulation of genes MYC and cyclinD1. Is negatively regulated by APC

Question 14

What are some macroscopic descriptions of how colorectal cancers progress

Answer 14

Annular (craters), stenosing and ulcerating that are bulky, polyploid and exophytic