Cancer Cytogenetics - Intro, Methods, Nomenclature Flashcards Preview

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Flashcards in Cancer Cytogenetics - Intro, Methods, Nomenclature Deck (21)
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Name 4 example uses for cytogenetics in cancer diagnostics & treatment.

1. Making diagnosis and classifications
2. Risk stratification / prognostication
3. Identifying targetable therapies
4. Monitoring effects of therapy or disease progression


Describe "Class I" and "Class II" mutations in hematologic malignancies.

Class I: Gives proliferative or survival advantage

Class II: Blocks differentation


Define: Clone

A cell population derived from a single progenitor.


Define: Recurring abnormality

A numerical or structural abnormality noted in multiple patients who have a similar disease.


Define: Modal number

The most common chromosome number in a tumor population.


In what number of cells must the following abnormalities be seen to be called?
- Structural rearrangement
- Chromosomal gain
- Chromosomal loss

Rearrangement - Two cells
Chromosomal gain - Two cells
Chromosomal loss - Three cells (can lose chromosomes when dropping)


- cen
- i
- mar
- der
- add

cen - centromere
i - isochromosome
mar - marker chromosome
der - derivative chromosome
add - additional material


What is an isochromosome?

A chromosome with two copies of one arm due to loss and duplication.


What is a marker chromosome?

A chromosome that cannot be identified in karyotyping.


What is a derivative chromosome?

Basically, a very rearranged chromosome.


What is the difference between "-" and "del"?

"del" refers to a terminal or interstitial deletion, while "-" can refer to a deletion or whole chromosome loss. "-" should not be used in karyotypes to describe deletions.


Explain the region described by this nomenclature: 4q21.2

Chromosome 4
Long arm
Region 2
Band 1
Sub-band 2


In what ways is cancer cytogenetic analysis different than constitutional?

1. Culturing does not require mitogens and is done for a shorter period (cancer cells naturally proliferative)

2. Cell populations are heterogeneous

3. Chromosome morphology is worse.


What are some appropriate indications for cancer cytogenetics?

1. All leukemias & lymphomas, including evolving, relapsed, and residuals.

2. Follow-up samples at RD or CR (if diagnostic sample was abnormla)

3. Opposite-sex post-transplant samples.


What tissues can be used for cancer cytogenetics?

Bone marrow biopsies & aspirates

Lymph node and tumor mass biopsies

Peripheral blood

Effusions or CSF


BRIEFLY review the processing of tissue for cancer cytogenetics.

1. Short term culture

2. Harvest with colcemid arrest, hypotonic lysis, and 3:1 fixation.

3. Slide making by dropping, heating, and treatment with trypsin.

4. Banding or FISH.


What does G-banding highlight?

Dark bands: AT-rich and gene-poor regions

Light bands: GC-rich and gene-rich regions.


What are some advantages and weaknesses of FISH over karyotyping?

Pros: Doesn't require metaphases, higher sensitivity, faster/simpler and less subjective.

Cons: Targeted, limited number of probes.


Describe 3 FISH probe designs.

Counting signals (centromere probes)

Dual-fusion probes (detects translocations)

Break-apart probes


What are the strengths and weaknesses of SNP microarray analysis?

Pros: High-resolution, cost effective, and objective.

Cons: Does not detect balanced translocations or low-level mosaicism.


How does SNP microarray work?

By detection of SNP alleles to detect losses of heterozygosity, indicating chromosomal losses or gains.