Haematology (Haematological malignancies) Flashcards
What are the 4 main concequences of oncogenic mutations in blood stem cells?
1) Failure to produce effector cells
2) Accumulation of cells at a particular stage of maturation
3) An increased cellular proliferation rate
4) A failure of apoptosis to regulate cell numbers
What are the 5 types of haematological malignancies?
1) Leukemias
2) Lymphomas
3) Multiple myeloma
4) Myelodysplastic syndromes
5) Myeloproliferative disorders
What is leukaemia? What cells are affected?
Presence of malignant haematopoietic cells within the peripheral blood or bone marrow
Can be myeloid (RBCs, neutrophils, monocytes, eosinophils, basophils, platelets or their precursors) or lymhphoid (B or T cells, plasma cells, NK cells or their precursors))
Describe the characteristics of both acute and chronic leukemia
Acute:
- Lymphoblastic
- Accumulation of immature blasts (>20%)
- Aggressive, rapid onset of death
Chronic:
- Lymphocytic
- Lower blast accumulation (<20%)
- More differentiated
- Cells accumulate due to deregulation of apoptosis
- less aggressive
What is lymphoma?
Malignancy of lymphoid cells, largely restricted to lymphoid organs
What is the leukaemic stage of lymphoma?
Rare, tumour cells overspill into bone marrow or peripheral blood
What 2 categories can lymphoma be split into?
High grade or low grade based on rate of growth
- low grade more difficult to treat
What is Hodgkin lymphoma?
Associated with mutated B cell lineage known as the Hodgkin and Reed-Sternberg cell
What is Non-Hodgkin lymphoma?
Diverse group of solid lymphoid tumours
What is Multiple Myeloma?
- Malignancy associated with old age
- Hyperproliferation of plasma cells that reside in bone marrow
- Results in myelosuppression and activation of osteoclast
How may multiple myeloma cause kidney damage?
Antibodies secreted in large amounts - formation of macromolecular complexes which can damage kidneys
What is myelodysplastic syndrome?
- Range of heterogenous blood diseases restricted to myeloid lineage
- Associated with increased precurosrs in bone marrow (hypercellularity) with reduced numbers in the peripheral blood (cytopenia)
What is the result of myelodysplastic syndrome?
- Subject to infections
- may exhibit refractory macrocytic anemia (enlarged RBCs with reduced haemaglobin, not treatable with folate or iron)
- Increased risk of acute leukemia
What are myeloproliferative disorders?
Range of conditions affecting myeloid lineage
Name the 3 main myeloproliferative disorders
1) Polycythaemia
- proliferation of RBC precursors
2) Myelofibrosis
- proliferation of fibroblasts
3) Thrombocythaemia
- proliferation of megakaryocytes resulting in increased platelet count
What are the 3 main types of chromosome abnormalities associated with leukemia and lymphoma?
Translocation
Deletion
Inversion
Give an example of a translocation that results in leukemia
Reciprocal translocation between chromosome 9 and 22 creating the BCR-ABL fusion gene
- Philadelphia chromosome
- CML
What are Interstitial deletions, terminal deletions and microdeletions?
Interstitial - a deletion within a chromosome
Terminal - deletion at a chromosome tip
Microdeletions - small deletions that may be undetectable in a karyotype but may still be associated with malignancy
What are paracentric and pericentric inversions?
Paracentric - restricted to single arm
Pericentric - involves the centrosome
(see diagram on slide 9)
Describe the karyotype of both a male and a female with chronic lymphocytic leukaemia (CLL)
Male:
- Additional chromosome 12 (trisomy)
- Deletion of long arm of chromosome 13
Female:
- Trisomy 3 and 18
- Translocation from chromosome 7 to 11
What is epigenetics?
The study of alterations in gene expression
Give some examples of epigenetic modifications to nucleic acids
1) Hypermethylation - adding methyl groups, suppresses transcription
2) Hypomethylation - removal of methyl groups, increases oncogene expression
3) Acetylation (of histones)
4) Phosphorylation
5) Ubiquitination (of histones)
How does DNA methylation cause transcriptional repression?
1) Methylation of cytosine within promoter CpG island allows assembly of inhibitory complex involving histone deacetylase and sin3a
2) Complex causes chromatin remodelling by deacetylating histone h3 and h4 lysine residues
3) Activators that normally bind acetylated lysine fail to do so
4) Transcriptional repression
Are DNA methyltransferases over or under expressed in many haematological malignancies?
Over expressed
How do haematological malignancies grow and mutate?
By clonal evolution
What are the 3 main causes of genetic changes resulting in haematological malignancies?
1) Inheritance
2) Environmental
3) Infection
Give an example of an inherited syndrome that increases the incidence of haematological malignancy
Trisomy 21 (Downs Syndrome)
Give an example of an environmental factor that can increase the incidence of haematological malignancy?
Ionising radiation
Give some examples of infectious agents that can cause haematological malignancies
1) EBV
2) Human T-lymphotrophic virus (HTLV-1)
3) Human herpesvirus 8
4) Helicobacter pylori
What is the very first investigation of haematological malignancy?
Patient presentation (assessing symptoms)
What are some symptoms of haematological malignancies?
- Lethargy
- Recurrent infections
- Easy brusing
- Night sweats
- Flu like symptoms
- enlarged spleen and/or liver
What will the first test likely be?
Full blood count
- limited value, some malignancies do not change measures of cell number
Why may a blood film be used?
Do identify dysplasia (abnormal development)
What is a leucoerytheoblastic blood picture?
A blood film with immature red or white cells
Why is a bone marrow assessment essential?
- To asses the cellularity of the sample e.g normo-, hyper, or hypo cellular
- Comparison of cells in biopsy to a normal range
How is cytochemistry used in heamotological malignancy testing?
Use of microscopic techniques to assess the characterstics of cells following a range of cytochemical stains
What is the problem with cytochemistry?
Can be difficult to differentiate between myeloblasts and lymphoblasts
- may result in misclassification of the malignancy
What is immunophenotyping also known as? What has it largely replaced?
Flow cytometry
Largely replaced cytochemistry
What are the Bethesda Group recommendations for immunophenotyping?
Suggests cases where immunophenotyping should or shouldnt be used
For example:
Used for atypical cells or blasts present in the blood or bone marrow
Not used for basophilia, mature neutrophilia etc
How is immunophenotyping performed?
Monoclonal antibodies that bind to specific antigens are labelled with fluorochrome
Flow cytometer uses laser and detector to assess whether antibody has bound
What do forward scatter and side scatter measure?
Forward (x-axis): measures the size of the cells - further to the right = larger
Side scatter (y-axis) - measures internal complexity e.g granularity - the more complex, the higher up the axis
Colours represent different surface antigen e.g CD33 in AML
Example: Neutrophils are large and granular, so appear top right
What is cytogenetic analysis?
A fusion of cytology (study of cells) and genetics
What information may cytogenetics provide about haematological malignancies?
- Diagnosis
- Selection of optimal therapeutics
- Info on prognosis
- monitoring of disease progression
What cytogenetic analysis will be used first?
A karyotype to identify chromosome abnormalities in addition to Fluorescent in situ hybridisation (FISH)
When are these techniques not very useful?
When the genetic changes are minimal e.g. microdeletions or point mutations
What is used in the case of minimal genetic changes?
Molecular techniques such as PCR, DNA sequencing, microarray gene expression study
