Pathology Clinical Cases Flashcards
List the T subcategories for TNM staging of colorectal cancer.
- TX: Primary tumour cannot be assessed.
- T0: No evidence of primary tumour.
- T1: Tumour invades submucosa.
- T2: Tumour invades muscularis propria.
- T3: Tumour invades subserosa or non-peritonealised tissues.
- T4: Tumour perforates visceral peritoneum and / or directly invades other organs.
- If the tumour is present in the mucosa but does not invade the submucosa, it is a dysplasia (not a cancer).
List the N subcategories for TNM staging of colorectal cancer.
- NX: Regional lymph nodes cannot be assessed.
- N0: No regional lymph node metastatic disease.
- N1: Metastatic disease in 1-3 regional lymph nodes.
- N3: Metastatic disease in 4 or more lymph nodes.
List the M subcategories for TNM staging of colorectal cancer.
- MX: Metastasis cannot be measured.
- M0: Cancer has not spread to other parts of the body.
- M1: Cancer has spread to other parts of the body.
List the subtypes of colorectal adenocarcinomas.
Which subtype represents the majority of colorectal adenocarcinomas?
Colorectal adenocarcinomas are either:
1 - Microsatellite stable.
2 - Microsatellite instable.
- The majority (80%) are microsatellite stable.
Why might the presence microsatellite instabilities imply that there is further genetic damage?
- Microsatellites are usually corrected by DNA mismatch repair.
- If DNA mismatch repair is impaired, the microsatellites will remain.
- Therefore, the presence of microsatellite instabilities implies that there is a defect in the cell’s DNA repair mechanisms.
List 4 implications of microsatellite instability.
1 - Aneuploidy.
2 - Amplifications.
3 - Translocations.
4 - Mutations of genes controlling cell growth.
List 4 characteristics of highly microsatellite instable (MSI-H) tumours.
MSI-H tumours are:
1 - Proximal, with a well-defined border.
2 - Poorly differentiated.
3 - Mucinous when examined histologically.
4 - More likely to show lymphocytic infiltration.
Give an example of a disease that predisposes patients to highly microsatellite instable (MSI-H) tumours.
Hereditary non-polyposis colorectal cancer (Lynch syndrome) predisposes patients to highly microsatellite instable (MSI-H) tumours.
What inheritance pattern does HNPCC / Lynch syndrome show?
HNPCC / Lynch syndrome is an autosomal dominant disorder.
Which genes are affected in HNPCC / Lynch syndrome?
- Mismatch repair (MMR) genes are affected in HNPCC / Lynch syndrome. Examples include:
1 - MSH2.
2 - MSH6.
3 - MLH1.
In what proportion of colorectal tumours are RAS mutations present?
Why is this important clinically?
- RAS mutations are present in ~1/2 of all colorectal tumours.
- Patients with tumours that have mutations in RAS are unlikely to benefit from anti-epidermal growth factor receptor (anti-EGFR) antibodies (because the MAPK pathway is dysfunctional).
In what proportion of colorectal cancers are BRAF mutations present?
Why is this important clinically?
- BRAF mutations are present in 8% of all colorectal tumours.
- Patients with tumours that have mutations in BRAF usually have a poor prognosis (but for some reason it isn’t a negative marker for anti-EGFR therapy).
List the 2 subtypes of inflammatory bowel disease (IBD).
IBD includes:
1 - Crohn’s disease.
2 - Ulcerative colitis.
What is the primary difference between the distribution of affected lower GI tissue in Crohn’s disease and ulcerative colitis?
- In Crohn’s disease, it is usually the ileocaecal junction that is affected, but it can also occur in patches across the whole lower GI tract.
- In ulcerative colitis, it is usually the distal colon and rectum that are affected.
