Diagnosis and tests

Cytogenetics

The related article (“Cytogenetics: karyotype and FISH”) explains the blood count. This topic is about cytogenetics, the field that studies the chromosomes of leukaemia cells, and its role in diagnosis and outlook.

Last updated: 14 October 2026~1 min read

Chromosomes sorted by size. — **Figure 1.**Chromosomes arranged in pairs.

01Short answer

Cytogenetics studies the number and structure of chromosomes in cells. In leukaemia cells, chromosomes are often changed: a piece moves to another chromosome (translocation), a piece is lost (deletion) or flipped (inversion), or there is an extra chromosome. These changes confirm the diagnosis, help predict how the disease will behave and help choose treatment. The main cytogenetic methods are the classic karyotype (“Karyotype”), which looks at all the chromosomes, and FISH (“FISH”), which searches for a specific change. Molecular tests (“Molecular tests”) find smaller changes at the level of genes. The sample is usually taken from the bone marrow.

02Simple explanation

Chromosomes: number and structure.

Translocation, deletion: typical changes.

Important for outlook and treatment.

03Scientific explanation

Risk groups: in AML and ALL, cytogenetic findings help place a patient in a favourable, intermediate or high-risk group.

Complex karyotype: several changes together are usually linked to a more serious course.

04What happens in the body?

Chromosomes in pairs

People have 23 pairs of chromosomes; the lab arranges them by size.

A dividing cell

Chromosomes are clearly visible only while a cell divides.

Chromosomes gathered in the centre. — **Figure 2.**Chromosomes in a dividing cell.

A family of tests

Karyotype, FISH and molecular tests complement one another.

Three panels: karyotype, FISH, DNA. — **Figure 3.**A family of genetic tests.

05Cytogenetic analysis

Four steps.

1CultureCells are grown.

2PauseDivision is stopped.

3SpreadChromosomes onto a slide.

4ArrangePairs put in order.

06Chromosome changes

Type	Example
Translocation	t(9;22): CML, some ALL
Translocation	t(15;17): APL
Inversion	inv(16): AML
Deletion	del(17p): CLL
Extra chromosome	+12: CLL

07Key terms

Cytogenetics: The study of chromosomes.
Translocation: Chromosome pieces swapping places.
Deletion: Loss of part of a chromosome.
Inversion: A piece flipped around.
Complex karyotype: Several changes together.

08Key points

Cytogenetics looks at chromosomes.
Changes are common in leukaemia.
They affect the outlook.
They help choose treatment.
Results take days to weeks.
They are read with other tests.

09Frequently asked questions

Are these changes inherited?

No; they are usually present only in the leukaemia cells and are not passed to children.

Why does the result take so long?

The cells first have to be grown in the lab.

Is a normal karyotype good?

It may mean intermediate risk; molecular tests add more information (“Where molecular tests matter most”).

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

Are these changes inherited?
Why does the result take so long?
Is a normal karyotype good?

My questions

12Sources

National Cancer Institute (NCI). Definition: cytogenetic analysis
MedlinePlus Genetics. What is a chromosome?
National Cancer Institute (NCI). Adult AML treatment (PDQ), patient version
National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: tumor lysis syndrome
American Cancer Society. Second Opinions for Cancer Treatment
Leukemia, 2020. European LeukemiaNet 2020 recommendations for treating chronic myeloid leukemia
National Cancer Institute. NCI Dictionary of Cancer Terms: bone marrow aspiration
National Cancer Institute. NCI Dictionary of Cancer Terms: polymerase chain reaction
Cancer.Net (ASCO). Seeking a Second Opinion
MedlinePlus (U.S. National Library of Medicine). How to Understand Your Lab Results

Medical disclaimerThis information is for educational purposes only and does not replace medical advice.

Last updated: 14 October 2026← Back to the list

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