Theme 5: Gastrointestinal, Hepatobiliary and Pancreatic Pathology Flashcards
What is colorectal cancer?
A malignant neoplasm developing in the submucosa of the large bowel
In which section of bowel are colorectal cancers commonest?
Left side - sigmoid colon and rectum
The most common site of metastasis in bowel cancer is the ____.
liver
Over the past 40 years, have incidences of colorectal cancer increased or decreased? Is this the same for males and females?
Over the past 40 years, bowel cancer rates have increased for both males and females, though rates are higher in males.
What are the risk factors for bowel cancer?
Increased age More common in men Western populations Diet: high fat, red meat, low fibre Obesity Alcohol Smoking Ionising radiation exposure Genetics IBD
In the pathogenesis of colorectal cancer, what allows the advancement of the tumour from each stage to the next?
Genetic mutation/loss.
Vast majority of bowel cancers develop along the adenoma-carcinoma sequence, beginning as normal epithelium and advancing until it becomes metastatic disease.
At each stage, genomic events occur to allow progression. Not all event have to occur and not in a specific order, but multiple hits are required to develop into metastatic carcinoma.
Normal bowel mucosa contains regular, rounded glands.
Normal bowel mucosa contains regular, rounded glands. The nuclei are basally located and are roughly the same size and shape.
Adenomatous mucosa features irregularly-shaped glands. The nuclei are pseudostratified and much bigger, with varying sizes and shapes.
What are the two main ways in which colorectal cancer develops?
Adenoma-carcinoma sequence (85%)
Microsatellite instability (15%)
What allows microsatellite instability to occur?
Loss of function of the DNA-mismatch-repair genes.
DNA mismatch repair genes repair sporadic mutational damage throughout the genome.
What condition leads to increased susceptibility for developing colorectal cancer due to mutations in DNA mismatch
repair genes?
Lynch Syndrome
Also known as Hereditary Nonpolyposis Colorectal Cancer (HNPCC)
What histopathological clues indicate a tumour may be caused by microsatellite instability?
- Right-sided
- Mucinous
- Poorly differentiated
- Infiltration by immune cells
What are the key clinical implications associated with colorectal cancer?
- Ulceration: leading to bleeding. If on left side, this is normally noticed by patients. Blood from the right side changes colour during its bowel journey, and may not be noticed by patients. This is called occult bleeding (no signs/symptoms). Chronic bleeding leads to anaemia
- Stenosis: bowel obstruction, pain
- Weight loss and altered bowel habit
What is the normal treatment for operable colorectal cancer?
Surgery to remove tumour, along with a margin of normal tissue on either side. The two ends of bowel and then anastomosed to maintain normal intestinal continuity.
If cancer is in rectum, anal sphincters may need to be removed. This requires permanent colostomy.
+/- preoperative radiotherapy
+/- postoperative chemotherapy
What has happened to trends in UK colorectal mortality rates over the past 40 years?
Mortality rates have decreased
- improved diagnosis and treatment
- better MDT involvement
- screening programme tests for occult blood in faeces
Define gastric cancer
Malignant neoplasm developing in the stomach (between the gastroesophageal junction and gastroduodenal junction)
True or false: gastric cancer is relatively rare.
True. Gastric cancer is only the 16th commonest cancer in the UK (6,700 cases per year).
What risk factors are associated with gastric cancer?
- More common with age
- More common in men than women (2:1)
- Diet: smoked/cured meat and fish, pickled foods
- Alcohol
- Smoking
- Obesity
- H Pylori infection
- Bile reflux/ low levels of stomach acid
- Family history
True or false: H Pylori infection is associated with carcinoma of the gastroesophageal junction?
False. H Pylori is associated with carcinomas of the gastric body/antrum, but not the GOJ.
White males are associated with being most at risk of developing which type of gastric cancer?
Carcinoma of Gastroesophageal Junction
What are the key pathogenic factors associated with carcinoma of the gastroesophageal junction?
White Males
Gastroesophageal reflux
Obesity
What are the key pathogenic factors associated with carcinoma of the gastric body/antrum?
H Pylori infection
Diet (high salt, low fibre)
Why have incidences of gastroesophageal junction carcinoma increased in recent years?
Increased rates of obesity and GO reflux
Why have incidences of gastric body/antrum carcinoma decreased in recent years?
Eradication of helicobacter
What are the two histopathological classifications of gastric cancer?
Intestinal type:
- Appears similar to normal glands
- Well-moderately differentiated
- May undergo intestinal metaplasia and adenoma steps
Diffuse type:
- Poorly differentiated
- Scattered growth
- Does not form glandular structures
- Cadherin loss (mutation of E-Cadherin gene)
What key clinical features are associated with gastric cancer?
Dependent on type and site of tumour.
- Dysphagia (difficulty swallowing) if tumour obstructs gastroesophageal junction
- Weight loss
- Indigestion
- Feeling full after small amount of food
- Vomiting
- Bleeding: haematemesis/melaena
How is gastric cancer diagnosed?
Endoscopy to visualise/biopsy neoplasm
How is gastric cancer treated?
Local excision
- Small, early staged tumours can be dissected out
Gastrectomy
- for advanced tumours
- partial or total gastrectomy
Chemotherapy
What are the mortality rates like for gastric cancer?
20% 5-year survival from diagnosis
- Diagnosis occurring too late
What epithelium normally covers the lumen of the oesophagus?
Non-keratinised stratified squamous
What is oesophagitis?
Inflammation of the oesophagus.
May be acute or chronic.
What are the main causes of oesophagitis?
Infection: bacterial, viral (HSV1, CMV), fungal (candida)
Chemicals:
- Ingestions of corrosive substance
- Gastric reflux