Cancer as a Disease – Colorectal Cancer Flashcards

1
Q

What type of carcinoma are most colon cancers?

A

Adenocarcinoma

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2
Q

What is the rate of turnover of cells in the colon?

A

2-5 million cells per minute

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3
Q

What is a polyp?

A

Any projection from a mucosal surface into a hollow viscus

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4
Q

What is an adenoma?

A

Benign neoplasm of the mucosal epithelial cells

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5
Q

What are the different types of colonic polyp?

A

Metaplastic/hyperplastic

Adenoma

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6
Q

State some characteristics of hyperplastic polyps.

A

These are VERY COMMON
90% of all colonic polyps
They have NO malignant potential
15% have K-ras mutations

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7
Q

What are the different types of colonic adenoma?

A

Tubular
Tubulovillous
Villous
NOTE: the more villous it is the worse it is

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8
Q

What are the different shapes of colonic adenomas?

A

Pedunculated – looks like a tree

Sessile – looks like a hedge

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9
Q

What is the difference between tubular and villous adenomas?

A

Tubular– COLUMNAR cells with nuclear enlargement, elongation, multi-layering and loss of polarity + increased proliferative activity + reduced differentiation
Villous– MUCINOUS cells with nuclear enlargement, elongation, multi-layering and loss of polarity. May be exophytic.

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10
Q

What is the most famous condition that causes an increased number of colonic polyps?

A

Familial Adenomatous Polyposis

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11
Q

What gene mutation is FAP caused by?

A

5q21

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12
Q

What are the two genetic pathways in colorectal cancer?

A

Adenoma-carcinoma sequence = presence of adenomas will increase the risk of colorectal cancer
Microsatellite instability

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13
Q

What are microsatellites?

A

Repeat sequences of DNA that are prone to misalignment

Some microsatellites are found in coding sequences of genes which inhibit growth or are involved in apoptosis

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14
Q

State two genetic diseases that predispose to colorectal cancer.

A

Familial adenomatous polyposis – inactivation of the APC tumour suppressor gene
HNPCC – microsatellite instability (affects mismatch repair genes)

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15
Q

State some dietary factors that can increase the risk of colorectal cancer.

A

High fat
Low fibre
High red meat
Refined carbohydrates

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16
Q

State two dietary deficiencies that can increase the risk ofcolorectal cancer.

A

Folates– important for nucleotide synthesis and DNA methylation
MTHFR– deficiency leads to disruption of DNA synthesis and DNA instability

17
Q

What is the clinical presentation of colorectal cancer?

A

Change in bowel habit
PR bleeding
Unexplained iron deficiency anaemia

18
Q

Describe the Dukes classification of colorectal cancers.

A
Dukes A  
 Growth is limited to the wall (muscularis propria) 
 Nodes negative 
Dukes B  
 Growth beyond the muscularis propria 
 Nodes negative 
Dukes C1 
 Nodes positive 
 Apical nodes negative 
Dukes C2  
 Apical nodes positive
19
Q

State some clinical features that decrease the prognosis of colorectal cancer.

A

Bowel obstruction
Age < 30
Distant metastases

20
Q

State some pathological features that affect the prognosis of colorectal cancer.

A

Depth of bowel wall penetration
Number of regional lymph nodes involved
Venous invasion
Lymphatic invasion

21
Q

What are the criteria for a screening programme?

A

Condition should be important with respect to the seriousness and/or frequency
The natural history of the disease must be known in order to: Identify where screening can take place
To enable the effects of any intervention to be assessed

22
Q

What are the characteristics of a screening test?

A

Simple and acceptable to the patient
Sensitive and selective
Cost effective
Screening population should have equal access to the screening procedure

23
Q

What does the NHS colorectal cancer screening look for?

A

Faecal occult blood (FOB)
If positive and 55-60 years = sigmoidoscopy
If positive and over 60 years = full colonoscopy

24
Q

Function of APC

A

Regulates mitosis, migration and maintenance of genome stability