Cancer as a Disease – Colorectal Cancer Flashcards
What type of carcinoma are most colon cancers?
Adenocarcinoma
What is the rate of turnover of cells in the colon?
2-5 million cells per minute
What is a polyp?
Any projection from a mucosal surface into a hollow viscus
What is an adenoma?
Benign neoplasm of the mucosal epithelial cells
What are the different types of colonic polyp?
Metaplastic/hyperplastic
Adenoma
State some characteristics of hyperplastic polyps.
These are VERY COMMON
90% of all colonic polyps
They have NO malignant potential
15% have K-ras mutations
What are the different types of colonic adenoma?
Tubular
Tubulovillous
Villous
NOTE: the more villous it is the worse it is
What are the different shapes of colonic adenomas?
Pedunculated – looks like a tree
Sessile – looks like a hedge
What is the difference between tubular and villous adenomas?
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.
What is the most famous condition that causes an increased number of colonic polyps?
Familial Adenomatous Polyposis
What gene mutation is FAP caused by?
5q21
What are the two genetic pathways in colorectal cancer?
Adenoma-carcinoma sequence = presence of adenomas will increase the risk of colorectal cancer
Microsatellite instability
What are microsatellites?
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
State two genetic diseases that predispose to colorectal cancer.
Familial adenomatous polyposis – inactivation of the APC tumour suppressor gene
HNPCC – microsatellite instability (affects mismatch repair genes)
State some dietary factors that can increase the risk of colorectal cancer.
High fat
Low fibre
High red meat
Refined carbohydrates