Cancer: Colorectal cancer Flashcards
How common is colon cancer worldwide?
4th most common cancer overall
What rank is colon cancer as the cause of death in cancers?
2nd (behind lung cancer)
Describe two features of a normal large bowel
Mucosa is folded but smooth
There is a thick muscle layer (muscularis)
How many cells die per minute in the colon?
2-5 million
What does the APC gene do?
Adenoamtous polyposis coli gene product reduces risk of mutation during replication
Name three protective mechanisms to eliminate genetically defective cells
Natural cell loss
DNA monitors
Repair enzymes
Define a polyp
Any projection from a mucosal surface into a hollow viscus, and may be hyperplastic, neoplastic, inflammatory, hamartomatous etc.
Define an adenoma
Benign neoplasm of the mucosal epithelial cells (or more generally just glandular cells in epithelial tissue)
Describe features of hyperplastic polyps, and their prevalence
They are very common, making up 90% of all colonic polyps
There are often multiple polyps
They have NO MALIGNANT POTENTIAL
15% have K-Ras mutations
Name the three colonic adenoma types
Tubular (75% tubular) - common
Tubulovillous (25-50% villous) - rare
Villous (>50% villous) - very rare
If an adenoma is villous is this better or worse for the prognosis?
Worse
Name the shapes of adenomas
Pedunculated
Sessile
Describe pedunculated adenomas
On a stalk, look a bit like a tree
Describe sessile adenomas
Flat and raised, like a thick plush rug
Describe the microscopic structures of tubular adenomas
Columnar cells with nuclear enlargement, elongation, multi-layering and loss of polarity
Increased proliferative activity
Reduced differentiation
Complexity/disorganisation of architecture
Describe the microscopic structure of villous adenomas
Mucinous cells with nuclear enlargement, elongation, multi-layering and loss of polarity
Exophytic - growing outwards
Rarely may have hyper-secretory function and result in excess mucus discharge and hypokalaemia
Define dysplasia
Abnormal growth of cells with some features of cancer
Can be low and high grade
Name the most famous condition that increases the number of polyps
FAP (familial adenomatous polyposis)
5q21 gene mutation
