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Gastrointestinal Pathology > Colorectal Cancer and Screening > Flashcards

Colorectal Cancer and Screening Flashcards

1
Q

What % of colorectal cancers are adenocarcinomas?

A

95%

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2
Q

What % of colorectal cancers are due to IBD?

A

1%

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3
Q

What inheritable conditions are related to colon cancer?

A

HNPCC (5%)
FAP < 1%
Other CRC syndromes

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4
Q

Risk factors for colon cancer

A 
Genetics
Age
Male 
Previous adenocarcinoma/CRC
Diet
- decreased fibre
- decreased fruit and veg 
- decreased calcium 
- increased red meat 
- increased alcohol 
Obesity
Lack of exercise
Smoking
DM
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5
Q

What do the majority of colorectal cancers arise from?

A

Pre-existing polyps

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6
Q

Types of colorectal polyps

A

Epithelial

Mesenchymal

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7
Q

Histological types of colorectal adenomas

A

Tubular (75%)
Villous (10%)
Intermediate tubulovillous (15%)

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8
Q

Molecular sequence of colorectal adeno carcinoma

A

Activation of oncogene - k-ras, c-myc
Loss of tumour suppressor gene - APC, p53, DCC
Defective DNA repair pathway genes; microsatellite instability
Cell growth proliferation apoptosis

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9
Q

Presentation of colorectal cancer

A 
Rectal bleeding
Altered bowel opening - diarrhoea
Iron deficiency anaemia
- men of any age
- non menstruating women 
Palpable rectal or right lower abdominal mass
Acute colonic obstruction if stenosing tumour 
Weight Loss
Anorexia
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10
Q

Who should you investigate with specific symptoms indicative of colorectal cancer?

A

Rectal bleeding or diarrhoea

  • each symptom on its own investigation if > 60 y/o
  • combined symptoms investigate if > 40
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11
Q

If non menstruating women have iron deficiency anaemia, what malignancy are they most likely to get?

A

Right sided colonic malignancy

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12
Q

Investigation for colon cancer

A

Colonoscopy
Barium enema
CT colonography
Ionising radiation

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13
Q

Risks of colonoscopy

A

Perforation
Bleeding
Can exacerbate renal failure

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14
Q

Prevention of colorectal cancer

A

Lose weight
Exercise
Fruit and Veg

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15
Q

Who is screened for colon cancer?

A

Average risk population

High risk groups

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16
Q

Aim of population screening

A

Detect pre-malignancy adenomas/early cancer in the general population

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17
Q

What tests are done for the population screening of colon cancer?

A 
FOBT
FIT
Flexible sigmoidoscopy 
Colonoscopy 
CT colonography
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18
Q

What does FOBT stand for?

A

Faecal occult blood test

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19
Q

What does FIT stand for?

A

Faecal immunochemical test

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20
Q

Why would a flexible sigmoidoscopy be done in population screening for colon cancer?

A

2/3rds of cancer are in the left colon so can do a more focused search in just in that area

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21
Q

Features of Scottish bowel screening programme

A

Age 50 - 74 days
FOBT every 2 years
FOBT positive => colonoscopy

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22
Q

What % does Scottish bowel screening programme give a reduction of risk in colorectal cancer mortality?

A

15%

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23
Q

Heritable conditions for colorectal cancer

A

FAP

HNPCC

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24
Q

What does FAP stand for?

A

Familial adenomatous polyposis

25
What HNPCC stand for?
Hereditary non polyposis colorectal cancer
26
Who are at risk of colorectal cancer?
``` FAP HNPCC IBD Familial risk Previous adenocarcinomas/colorectal cancer ```
27
What is the inheritance of FAP?
Autosomal dominant
28
What happens in FAP?
Multiple (>100) adenomas throughout colon - 50% by 15 y/o - 95% by 25 y/o High risk of malignant change in early adulthood, in almost all cases by age 40 years old if untreated
29
What is the genetic change in FAP?
APC gene on chromosome 5
30
Screening in have FAP
Annual colonoscopy from age 10-12 years
31
If a significant number of polyps is found on screening for FAP, what can be done?
Prophylactic protocolectomy
32
What age is a prophylactic protocolectomy usually done in FAP?
16-25 years old
33
Extracolonic manifestations of FAP
``` Benign gastric fundic cystic hyperplastic polyps (benign in stomach) Duodenal adenomas (approx. 90% in periampullary cancer 5%) ```
34
What % of FAP gives rise to desmoid tumours?
10 - 20%
35
Definition of desmoid tumour
Non cancerous growths that occur in the connective tissue
36
What does CHRPE stand for?
Congenital retinal hypertrophy of the pigment epithelia
37
Treatment of FAP
Prophylactic proctocolectomy | NSAIDs chemoprevention
38
Role of NSAIDs chemoprevention in FAP
Sulindac reduces polyp number and prevents recurrence of higher grade adenomas in the retained rectal segment Reduces the rate at which polyps grow in GIT and rectum
39
Inheritance of HNPCC
Autosomal dominant
40
Pathology of HNPCC
Tumours have a molecular characteristic called microsatellite instability (MSI) - frequent mutations in short repeated sequences of DNA (microsatellites)
41
Genetics of HNPCC
Mutation in DNA mismatch repair (MMR) genes, e.g. MLH1 and MSH2
42
Presentation of HNPCC
Early onset colorectal cancer (40s) right sided
43
What side of the colon does HNPCC occur?
Mostly right sided
44
Assosiated cancers of HNPCC
Endometrial Genitourinary Stomach Pancreas
45
Diagnosis of HNPCC
Clinical criteria (Amsterdam/Bethesda) genetic testing
46
Screening in HNPCC
From age 25 - 2 yearly colonoscopy
47
Which of FAP and HNPCC has a higher risk?
FAP
48
When is there a high moderate risk of a familial history of CRC?
CRC in first degree relative kinship, None < 50 y/o | CRC in 2 first degree relatives in kinship, mean < 60 y/o
49
Screening of high moderate risk of familial history of CRC
5 yearly colonoscopy from age 50 years
50
When is there a low moderate risk of familial CRC?
CRC in 2nd degree relatives > 60 years in 1 first degree relative < 50 y/o
51
How often should a patient get a colonoscopy if have had previous CRC?
5 yearly
52
How often should familial high risk groups get colonoscopy?
``` 10 years post diagnosis Then dependent on - duration - extent - activity of inflammation - presence of inflammation ```
53
Treatment of colorectal cancer
Surgery Stoma formation (colostomy) Chemotherapy Radiotherapy
54
What would be the palliative care for colorectal cancer?
Chemotherapy | Colonic stenting to prevent colonic obstruction
55
What is the staging of colorectal cancer?
Dukes staging
56
5 year survival of the different Dukes staging
``` A = 83% B = 64% C = 38% D = 3% ```
57
What are villous adenomas?
Colonic polyps with the potential to become malignant
58
Presentation of villous adenomas
``` Characteristically secrete large amounts of mucous which can cause electrolyte disturbances Vast majority asymptomatic Non specific lower GI symptoms Secretory diarrhoea may occur Microcytic anaemia Hypokalaemia ```

Gastrointestinal Pathology (26 decks)

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