Cancer as a disease- colorectal cancer Flashcards
Where does colorectal cancer in terms of the most common cancer?
4th
Where does colorectal cancer come in terms of leading cause of cancer death?
2nd
What is the function of the colon?
Extraction of water from the faeces (electrolyte balance)
Faecal reservoir (evolutionary advantage)
Bacterial digestion for vitamins (vitamin B and K)
What is the mucosa like in a normal large bowel?
Folded but smooth
What types of cancer are cancers in the colon?
Adenocarcinomas (glandular epithelium)
What is the normal life of a cell in the colon?
They divide in crypts where stem cells are found and then they are shunted up to the top of the villus where they are shed
What is the turnover of colonic epithelium?
2-5 million cells die per minute in the colon
What does the high rate of cell proliferation mean?
Cells are vulnerable
What does the APC gene do?
Reduces the risk of mistakes during replication
What protective mechanisms are there to eliminate genetically defective cells?
Natural loss
DNA monitors
Repair enzymes
What is a polyp?
Any projection from a mucosal surface into a hollow viscus and may be hyperplastic, neoplastic, inflammatory, hamartomatous etc
What is an adenoma?
Benign neoplasm of mucosal epithelial cells
What different types of colonic polyps are there?
Metaplastic/hyperplastic
Adenomas
Juvenile, Peutz jeghers and lipomas
How common are hyperplastic polyps?
Very- 90% of all colonic polyps
What size are hyperplastic polyps?
<0.5cm
How malignant are hyperplastic polyps?
No malignant potential- 15% have K-ras mutations
What types of colonic adenoma are there?
Tubular- 90% (>75% tubular)
Tubulovillous- 10% (25-50% villous)
Villous- (>50% villous)
What type of colonic adenoma is worse?
The more villous it is, the worse it is
What different shapes of adenoma are there?
Pedunculate- on a stalk and look a bit like a tree
Sessile adenomas are flat and raised
What is the microscopic structure of tubular adenoma like?
Columnar cells with nuclear enlargement, elongation, multi-layering and loss of polarity
What is the proliferative activity and differentiation of tubular adenomas like?
Increased proliferative activity
Reduced differentiation
What is the microscopic structure of villous adenoma like?
Mucinous cell with nuclear enlargement, elongation, multi-layering and loss of polarity
Exophytic and may have hyper secretory function and result in excess mucus discharge and hypokalaemia
What does exophytic mean?
Frond-like extension
What is dysplasia?
Abnormal growth of cells with some features of cancer- indefinite