Oncology Cytogenetics Flashcards
What is the clinical importance of cancer cytogenetics? State as many as possible.
Can provide;
- a diagnosis
- monitor the disease
- predict or confirm relapse
- confirm remission
- provide a prognosis
- predict or confirm progression
- direct treatment
- monitor treatment
- management of patient.
What does immunophenotyping involve? Briefly how does it work?
Looking at cell surface markers to identify the cell and its lineage.
Uses fluorescently labelled antibodies which bind to particular cell types dependent on the antigen on the cell surface.
Can be looked at manually or detected by flow cytometry to count each cell type.
Some antibodies are polyclonal and recognise multiple cell types, others are monoclonal but these are more expensive.
What is immunophenotyping particularly useful for?
Identifying lymphoid cells which are indistinguishable by morphology staining.
What is bone marrow morphology study? What can it identify?
Using stains to identify which cells are present in a marrow or blood smear.
Looks at: shapes of cells e.g. tear drop, cell types visible, the way a cell stains,
Can see if any dysplastic cells are present in the smear/film e.g. if the morphology of a particular cell type is abnormal this can provide a clue as to the underlying disease.
What is an auer rod?
An example of usefulness of morphology.
Only ever seen in myeloblasts! So presence can confirm myeloid lineage.
Needle like body seen in the cytoplasms of myeloblasts and/or progranulocytes.
What numbers of cells are required to report something as a clonal abnormality?
3 or more cells with a loss
2 or more cells with a gain or structural abnormality
What kinds of genes are involved in cancer?
Proto-oncogenes
Tumour supressor genes
What is a proto-oncogene?
Often encode proteins which function to stimulate cell division, differentiation and halt cell death e.g. normal housekeeping functions.
Potential to cause cancer when mutated or rearranged.
Mutations etc are dominant.
How can a proto-oncogene cause cancer? Give an example of each.
Structural changes such as a translocation that creates a fusion protein or a mutation E.g. BCR/ABL
Amplification or gain of the proto-oncogene (includes trisomy).
Deregulated expression such as movement of the gene close to an inappropriate control gene e.g. MYC in the t(8;14) - position effect
What is a tumour suppressor gene?
Gene that restrains inappropriate cell growth and division.
Stimulates cell death.
Acts as the brakes to stop cells before they turn cancerous - e.g. prevents replication of damaged DNA.
They are recessive - both copies need to be damaged before the cell will turn cancerous.
How is a tumour supressor gene implicated in cancer? Give an example.
When both copies are lost then uncontrolled proliferation can occur e.g. no checkpoint in place to control growth.
Example is P53 - implicated in many cancers!
MLH1 could also be an example - involved in DNA repair.
What is EGFR? What service of ours is it relevant to?
Proto-oncogene.
Epidermal growth factor receptor.
Cell surface receptor: bridges communication between extra cellular environment and the inside of the cell.
Helps cell respond to outside environment.
If this pathway become mutated then cells receive a constant signal to proliferate.
Relevant to the RAS samples - patients with wild type RAS respond to EGFR inhibitor.
What does leukemia mean?
A disease of the blood forming tissue where there are large numbers of abnormal cells or where production of a cell lineage is out of control.
