13: Colorectal Cancer Flashcards
Difference between polyp and adenoma?
Polyp = Any projection from mucosal surface into a hollow viscus, may be hyperplastic/neoplastic/inflammatory etc..
Adenoma = benign neoplasm of mucosal epithelial cells
What are hyperplastic polyps?
Very common, 90% of all large intestine polyps
No malignant potential
Often multiple
Colonic adenoma types
Tubular (most common)
Tubulovillous
Villous
Pedunculated
Sessile
Structure of tubular adenomas
Columnar cells Nuclear enlargement Elongation, multi-layering, loss of polarity Increased proliferative activity Reduced differentiation Disorganised architecture
Structure of villous adenomas
Mucinous cells
Finger-like extensions
What condition increases risk of dysplasia?
Ulceritive Colitis - due to ongoing inflammation
What condition increases risk of dysplasia?
Ulceritive Colitis - due to ongoing inflammation
Pathology of Adenomatous Polyposis Coli (APC)
5q21 mutation
What is the principle of adenoma-carcinoma sequence?
Gradual accumulation of genetic abnormalities eventually progressing from adenoma to carcinoma
Genetic pathways for cancer?
Adenoma-carcinoma sequence (develop adenoma FIRST)
APC gene, K-ras, p53
Microsatellite instability:
Involved in gene repair
Repeat sequences prone to misalignment
2 main genetic pathways
FAP - Inactivation of APC tumour suppressor genes
HNPCC - microsatellite instability
Colonic carcinoma epidemiology
35000 per year in UK
10% of cancer deaths
Mostly age 50-80
Diet factors: High fat/red meat, low fibre
Clinical presentation
Change in bowel habit Bleeding PR (rectal) Unexplained iron deficiency anaemia
Macroscopic features?
Small carcinomas may be present WITHIN larger polypoid adenomas
Most common place where CRC occurs?
Rectosigmoid (most common)
What kind of tumours do you get?
Adenocarcinomas (glandular epithelial tissue)
Other rare:
Neuroendocrine
Mucinous carcinomas
How are they graded?
Well differentiated
Moderately differentiated (most common)
Poorly differentiated
What is Duke’s classification?
Dukes A = limited to wall (nodes negative)
Dukes B = growth beyond muscularis propria
Dukes C1 = nodes POSITIVE, apical node negative
Dukes C2 = apical node positive
If lymph nodes affected at all, graded C
Types of screening?
High risk screening
- Previous adenoma
- UC or Crohn’s disease
- Hereditary traits
Population screening
How is screening done for CRC?
Fecal occult blood (FOB) Assess stool for blood If there is: 55-60 = sigmoidoscopy 60-75 (older) = colonoscopy
