Colorectal Cancer Flashcards
What are most colorectal cancers?
Adenocarcinomas
Where do colorectal cancers originate from?
Epithelial cells lining colon / rectum
What is the pathophysiology sequence of colorectal cancer called?
Adenoma-carcinoma sequence
What is the adenoma-carcinoma sequence for colorectal cancer? (3 steps)
- Normal mucosa
- Colonic adenoma (colorectal polyps)
- Invasive adenocarcinoma
What are the genetic mutations causing colorectal cancer? (2 things)
- Adenomatous Polyposis Coli (APC)
- Hereditary NonPolyposis Colorectal Cancer (HNPCC)
What is the Adenomatous Polyposis Coli (APC) gene responsible for?
What happens when it is mutated?
APC gene = tumour suppressor gene
Mutation –> adenomatous tissue growth (e.g FAP aka Familial Adenomatous Polyposis)
What is the Hereditary NonPolyposis Colorectal Cancer (HNPCC) gene responsible for?
What happens when it is mutated?
HNPCC gene = DNA mismatch repair gene
Mutation –> DNA repair defects (e.g Lynch syndrome)
What percentage of colorectal cancers are sporadic (develop with no risk factors)?
75%
What are the risk factors for colorectal cancer? (7 things)
- Male
- Age
- FHx
- IBD
- Low fibre diet
- Smoking
- Alcohol
What are the clinical features of LEFT sided colorectal cancers? (4 things)
- Bleeding / mucus @ PR
- Change in bowel habits / obst
- Tenesmus
- Palpable LIF mass @ PR
What are the clinical features of RIGHT sided colorectal cancers? (4 things)
- Weight loss
- Abd pain
- Low Hb
- Iron deficiency anaemia symptoms
Why does impeded stool passage happen more in LEFT colon cancer than RIGHT? (3 things)
- R = stool still liquid (@ ileocecal valve –> asc colon)
- R = lumen is larger
- L = stool becomes formed here (@transverse colon - desc colon)
What are some differentials that present similarly to colorectal cancer? (2 things)
- IBD
- Haemorrhoids
How do you differentiate between IBD and Colorectal cancer? (2 things)
- IBD = presents younger (20-40 yrs)
- IBD = diarrhoea w blood + mucus
How do you differentiate between Haemorrhoids and Colorectal cancer?
Haemorrhoids = bright red rectal bleeding on stool surface
What lab tests should be done for suspected colorectal cancer? (3 things)
- FBC (will show microcytic anaemia, iron deficiency anaemia)
- LFTs
- Clotting