Pathologies of the Digestive Tract Flashcards
1
Q
What are the environmental risk factors for Bowel Cancer?
A
- Food rich in red meat and fat increase the risk of bowel cancer
- Food rich in vegetables, fruit & fibre reduces the risk of bowel cancer (better bowel movements)
- Physical activity and a low BMI are associated with low risk of bowel cancer
2
Q
What are non-environmental risk factors for Bowel Cancer?
A
- Longstanding Ulcerative colitis and to a lesser extent Crohn’s disease
- Presence of adenoma in the large bowel
- Previous history of bowel cancer surgery
- Family Hx
- Old age
3
Q
How does a high fibre diet reduce bowel cancer?
A
- increases the formation of short-chain fatty acids
- promotes healthy gut micro-organisms
- reduces proliferation of neoplastic cells
- increases the stool bulk, reduces transit time
- potential carcinogens in the stool have a shorter contact with the bowel mucosa
- reduces the formation of secondary bile acids which are potentially carcinogenic
4
Q
What is a Polyp?
A
- a protruding growth into a hollow viscus
- can be benign, adenoma or malignant
- can be innocent or precancerous in a cancer screening
- Most polyps in the large bowel are adenomas: pre-cancerous lesions and consist of dysplastic epithelium
5
Q
What is Dysplasia?
A
Cells that have morphological features of cancer but without invasion of the surrounding tissue
- low-grade dysplasia: early precancerous features
- High-grade dysplasia: advanced precancerous features with a high risk of invasion if not removed
6
Q
What are the pathological features of polyps?
A
- Hyperplastic: consists of numerous goblet cells compare to normal mucosa
- has a lace-like pattern
- Tubular adenoma has a test tube-like appearance
- Villous adenoma has a finger-like appearance
- Tubulovillous adenoma has a mixture of tubular and villous features
7
Q
What is the Adenoma-Carcinoma sequence?
A
- the stepwise progression from normal mucosa to adenoma to cancer
- carcinoma of the bowel is a good example of this
8
Q
What is Familial Adenomatous Polyposis?
A
- Herefitary autosomal dominant condition
- defective Chr5q21 aka the APC gene
- ‘first hit’ occurs in utero in a germ cell mutation
- ‘second hit’ occurs in the somatic cell mutations
- polyps developed at a young age
- patients have hundreds to thousands of polyps in a large bowel
- minimum of 100 polyps required to make a FAP diagnosis
- 100% risk of developing cancer by age 30
- undergo prophylactic colectomy around 20yrs
- contribute to 1% of bowel cancer
9
Q
FAP: Familial Adenomatous Polyposis
What is the difference between FAP and Sporadic Adenoma
A
- in FAP the first hit happens in utero and the second hit happens in the somatic cells
- in Sporadic Adenoma both hits happen in the somatic cells before they develop the polyps
10
Q
What is the progression from normal mucosa to adenoma to cancer?
A
- Normal Mucosa
- Hyperprofliferative epithelium
- Early Adenoma
- Intermediate Adenoma
- Late adenoma
- Invasive Cancer
11
Q
Give 7 Genetic abnormalities associated with bowel cancer
A
- Lynch Syndrome
- Familial Adenomatous Polyposis (FAP)
- Attenuated FAP- less than 100 adenomas
- Familial Colorectal Cancer Type X: FCCX
- MUTYH Associated Polyposis: MAP
- Serrated Polyposis Syndrome ( rapid cancer development)
- Hamartomatous Polyposis Syndrome
12
Q
What is Lynch Syndrome?
A
- errors in mismatch (GT instead of GC) in the DNA causing microsatellite instability
- these are tandem repeat nucleotides involving
- MSH2 and MLH1 in 30% of cases also involve PMS1 and PMS2
- two hits required like in FAP
- Familial cancer largely affecting the Caecu and right colon
- presents before eh age of 50
- associated with endometrial, ovarian, small bowel and cancer of the urinary tract (ask about all types of cancer in family Hx)
- accounts for 2-3% of bowel cancer (more than FAP)
- there are no precursor polyps
13
Q
What is used to identify if a patient has Lynch Syndrome?
A
The Amsterdam Criteria
- 3 or more relatives with LS associated cancer
- one affected patient should be a first- degree relative
- one+ patient diagnosed before age 50
- two or more successive generations affected
- FAP should be excluded when diagnosing
- Tumours verified by pathological examination
14
Q
What are the symptoms of bowel cancer?
A
- Asymptomatic: detected during screening
- Change in bowel habit: constipation alternating with diarrhoea (bacterial growth –> liquefication of solid stool): Spurious Diarrhoea
- Bleeding from the rectum
- Anaemia: especially with cancer of the caecum due to slow occult blood loss
- Abdominal pain due to obstruction
15
Q
How is Bowel Cancer diagnosed?
A
- Hx and clinical examination
- Flexible Sigmoidoscopy, colonoscopy, biopsy
- CT colonography: for colonoscopy intolerant patients
- Histological examination of biopsy
- Staging CT scan for distal metastasis (spread to liver)
- MRI for rectal cancer: assess local spread
16
Q
What is the grading of Bowel cancer?
A
- Well-differentiated (A)
- resembles normal colonic mucosa (B)
- Moderately differentiated (C)
- most common
- Poorly differentiated (D)
- minimal to no glandular differentiation
