What are the 2 types of haematological malignancy?
- Leukaemias
- Lymphomas
What is leukaemia?
Tumours of the blood and haemopoietic lineages.
-myeloid/lymphoid
What is lymphoma?
Tumours of lymphocytes and the immune system.
How are molecular diagnostics used in haematological malignancies?
- Diagnosis
- Prognosis
- Treatment selection
- Disease monitoring
What techniques are used to define translocations in haematological malignancies? (2)
- PCR
- FISH
What type of translocation is normally seen in myeloid leukaemias?
Fusion gene translocation.
What technique is normally used for detecting myeloid leukaemias?
PCR.
- very sensitive and specific, small size range
- gene level
What is characteristic of the DNA in myeloid leukaemias?
Predictable break point/fusion.
-mRNA processed to remove introns
What type of translocation is normally seen in lymphomas?
Promoter/enhancer substitution.
What technique is normally used for detecting lymphomas?
FISH.
- very specific, large sizes
- chromosomal level
What is characteristic of the DNA in lymphomas?
Unpredictable break point/fusion.
-no abnormal mRNA
How common is chronic myeloid leukaemia?
Rare (1/100,000).
What are the main symptoms of chronic myeloid leukaemia?
- Abdominal pain
- Fatigue
- Gout
What causes abdominal pain with chronic myeloid leukaemia?
Splenomegaly/splenic infarction.
What causes fatigue with chronic myeloid leukaemia?
Anaemia.
What causes gout with chronic myeloid leukaemia?
Hyperuricaemia.
What does a FBC show if a patient has chronic myeloid leukaemia?
- Leucocytosis
- Anaemia
What is a common mutation in chronic myeloid leukaemia?
t(9,22)
» BCR-ABL fusion gene
» active tyrosine kinase
How is Gleevec (imatinic mesylate) used to treat chronic myeloid leukaemia?
Blocks the active site of BCR-ABL tyrosine kinase.
-competitive inhibitor
Which is more sensitive; PCR or cytogenetics?
PCR.
-can identify relapse early
What happens when someone is suffering from chronic myelogenous leukemia?
The bone marrow produces too many WBCs.
What common mutations are used to detect chronic myeloproliferative leukemia? (2)
- JAK2
- CMPD
Who is B-cell chronic lymphocytic leukaemia most common in?
Elderly males.
What are the common symptoms of B-cell chronic lymphocytic leukaemia?
- Asymptomatic
- Fatigue
- Autoimmune anaemia
- Splenomegaly
- Lymphadenopathy
What does a FBC show if someone is suffering from B-cell chronic lymphocytic leukaemia?
Lymphcytosis.
What is a common deletion for B-cell chronic lymphocytic leukaemia?
11q/17p deletion.
What type of mutation acts on Ig genes in B cells in B-cell chronic lymphocytic leukaemia?
Somatic hypermutation.
How are Ig genes sequenced?
Extract DNA
»PCR Ig genes
»compare to reference
How is FISH used to determine the prognosis of B-cell chronic lymphocytic leukaemia?
Denature and stain DNA
» count spots in nuclei.
2 per nucleus = amplified
What is the treatment process of B-cell chronic lymphocytic leukaemia if there is a mutated Ig but no deletions?
Monitoring and minimally toxic therapy.
What are the main stages in the B cell life cycle?
Progenitor B cell (generate functional antigen receptor)
» Mature B cell (hypermutation, class-switching)
» Plasma cell (proliferation)
What do overlapping signals on FISH suggest?
Fusion.
What do separated signals on FISH suggest?
ALK rearrangement.
What are biopsies fixed in and embedded in?
Fixed in formalin then embedded in paraffin.
What are biopsies stained with?
Haematoxylin and eosin.
H&E
What germline mutations are seen in hereditary nonpolyposis colorectal cancer (HNPCC)?
Mismatch repair proteins.
- function as dimers
- leads to microsatellite instability
What are the main mutation in colorectal cancer? (2)
- BRAF mutation (5-15%)
- KRAS mutation (30-45%)
Which type of mutation is more common in colorectal cancer; BRAF or KRAS?
KRAS.
What is the prognosis with a BRAF mutation?
Poor prognosis.
What does a KRAS mutation in colorectal cancer indicate?
Predicts a response to anti-EGFR therapies.
What is significant of colorectal cancers with mutations at codons 12, 13, 61, 117 and 146?
Resistant to anti-EGFR.
What is another name for hereditary nonpolyposis colorectal cancer?
Lynch syndrome.
What are microsatellites?
Non-encoding repeat regions of DNA.
What type of mutation is uncommon in somatic cancers?
A point mutation in both copies of a tumour suppressor gene.
What is the 2nd mutation in inherited cancers normally?
- Chromosomal deletions
- Promoter hypermethylation
What is microsatellite instability (MSI)?
A condition of genetic hypermutability that results from impaired DNA mismatch repair (MMR).
What proportion of colorectal cancers are microsatellite-instability high?
15%.
-better prognosis
What are the majority of colorectal cancers due to?
Epigenetic silencing of MLH1.
What is another name for Lynch syndrome?
Hereditary non-polyposis colorectal cancer (HNPCC).
What type of inheritance does Lynch syndrome have?
Autosomal dominant.
What does lynch syndrome predispose?
Increased risk of colon cancer.
-and ovarian/stomach/etc
What are common symptoms/signs of colorectal cancer? (4)
- Changed bowel habits
- Rectal bleeding
- Weight loss
- Abdominal pain
What are the red flag symptoms of colorectal cancer? (2)
- Rectal bleeding
- Weight loss
What are the risk factors of colorectal cancer?
- Male
- Age
- Obesity
- Smoking
- Red meat
- Polyps
- IBD
How can you reduce the risk of colorectal cancer? (3)
- Eat fruit/vegetables
- Increase fibre intake
- Aspirin
What proportion of colorectal cancer is sporadic?
90-95%.
-mainly spontaneous condition
What proportion of colorectal cancer is hereditary?
5-10%.
What are the main causes of hereditary colorectal cancer? (2)
- Familial Adenomatous Polyposis (FAP)
- HNPCC
What sort of inheritance does Familial Adenomatous Polyposis (FAP) have?
Autosomal dominant inheritance.
What gene causes to Familial Adenomatous Polyposis?
Adenomatous Polyposis Coli (APC) gene.
How many polyps do people with Familial Adenomatous Polyposis have?
100+.
At what age do people with Familial Adenomatous Polyposis (FAP) develop cancer?
- Tumours develop in ~2nd decade.
- Most develop carcinomas by 40.
What is the Vogelstein sequence?
The adenoma-carcinoma sequence of mutations in oncogenes and tumour suppressor genes that lead to colorectal cancer.
-in 85% of colorectal cancers
What is the general Vogelstein sequence?
Normal epithelium >> hyperproliferative epithelium >> early adenoma >> intermediate adenoma >> late adenoma >> carcinoma >> metastasis
What mutation causes a hyperproliferative epithelium in the development of colorectal cancer?
5q mutation.
What causes early adenoma in the development of colorectal cancer?
DNA hypomethylation.
What mutation causes intermediate adenoma in the development of colorectal cancer?
12p mutation.
-KRAS
What mutation causes late adenoma in the development of colorectal cancer?
18q loss.
What mutation causes carcinoma in the development of colorectal cancer?
17p loss, p53.
How does microsatellite instability pathway lead to HNPCC?
Mutations in one of six mismatch repair genes.
What are features of tumours that develop from HNPCC?
- Mucinous / poorly differentiated
- Prominent lymphocytic response
- Right-sided
What is the treatment of polyps?
- Polypectomy (endoscopic mucosal resection)
- Repeat colonoscopy
How frequently do new polyps develop after polypectomy?
30% within 26 months.
What is a polyp?
A tissue mass that protrudes into the bowel lumen.
Are polyps always neooplastic?
No.
-can be inflammatory, hyperplastic, etc
What is an adenoma?
Benign neoplasm of glandular epithelium.
How are colonic adenomas classified?
- Architecture (tubular, villous, tubulovillous)
- Degree of dysplasia (low/high grade)
Why are polyps clinically significant?
Precursors to colorectal cancer.
-majority evolve through polyps
What factors does the risk of colorectal cancer from polyps depend on? (3)
- Size (>1cm = high risk)
- Histological architecture (villous adenoma = high risk)
- Severity of dysplasia
Who is screened for bowel cancer?
60-69 year olds.
-faecal occult blood test
Where are the majority of colorectal cancers located?
Sigmoid colon (20%)
Rectum (27%)
Caecum (14%)
What are the main systems of staging colorectal cancer? (2)
- Tumour, Node, Metastasis (TNM)
- Dukes staging (A, B, C, D)
Which stage of Dukes has the best prognosis?
A has best prognosis, D has worst prognosis.
Who is treated for colorectal cancer?
- High risk stage II
- Stage III
What are metastases?
2* tumours distant to the site of origin.
What routes do tumours metastasise by? (3)
- Haematogenous (blood)
- Lymphatics
- Transcoelomic (pleural, pericardial, peritoneal)
Where do colorectal cancer tumours metastasise to? (3)
- Lymph nodes
- Liver
- Lungs
What proportion of colorectal cancer patients die?
~50%.
