← Back
Medical glossary

FISH: fluorescence in situ hybridisation

FISH uses glowing probes to make particular genes or chromosome breaks visible.

Last updated: ~1 min read
A cell nucleus under a fluorescence microscope with many small glowing red and a few green probe dots
Figure 1.FISH: glowing dots mark particular genes

01Short answer

The probes stick to the DNA region being sought and appear as coloured dots under the microscope. Two colours merging can reveal a fusion gene (for example BCR::ABL1); a missing or extra dot means a deletion or an extra copy. FISH is faster than a karyotype and works on cells that are not dividing, but it only sees what it is looking for.

02Simple explanation

Glowing probes.

Coloured dots.

Fast.

Sees only what is sought.

03Scientific explanation

NCI: FISH uses fluorescent dyes to see gene and chromosome changes in cells.

The NCI Dictionary explains cancer terms in plain language; check the exact meaning for your situation with your doctor.

04What happens in the body?

What it finds

Translocations, deletions and extra copies.

Fusion
Figure 2.Fusion — FISH: fluorescence in situ hybridisation

Limitation

It does not see unexpected changes.

The microscope
Figure 3.The microscope — FISH: fluorescence in situ hybridisation

Where you will see this word

In test results, discharge letters and conversations with your doctor. Write the word down and ask what it means.

Ask your doctor

The general meaning and the meaning of your own result can differ. The most important question is “What does this mean for me?”

05From an unfamiliar word to a clear answer: four steps

Write it down, look it up, prepare a question, ask.

Write it down — From a result or a conversation.1Write it downFrom a result or a conversation.
Look it up — Learn the plain meaning.2Look it upLearn the plain meaning.
Prepare a question — What does this mean for me?3Prepare a questionWhat does this mean for me?
Ask — Your doctor gives the personal explanation.4AskYour doctor gives the personal explanation.
UnderstandingResults feel less frightening.
ConversationA shared language with your doctor.
SafetyNot drawing conclusions alone.

06Key points at a glance

TopicIn brief
What it findsTranslocations, deletions and extra copies.
LimitationIt does not see unexpected changes.
Where you will see this wordIn test results, discharge letters and conversations with your doctor. Write the word down and ask what it means.
Ask your doctorThe general meaning and the meaning of your own result can differ. The most important question is “What does this mean for me?”

07Key terms

Probe
A labelled piece that sticks to specific DNA.
Translocation
Parts of chromosomes swapping places.
Term
A word with a precise medical meaning.
Reference range
The range a laboratory considers normal.

08Key points

  • Learn.
  • Ask your doctor.
  • Write it down.
  • Write the word down.
  • Ask what it means.

09Frequently asked questions

Are FISH and karyotype the same?

No, they complement each other.

When will the result come?

Usually within a few days.

This word is in my results: should I worry?

The word itself does not mean a serious or mild condition; get the explanation from your doctor.

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.

  1. Are FISH and karyotype the same?

  2. When will the result come?

  3. This word is in my results: should I worry?

My questions

12Sources

  1. National Cancer Institute. NCI Dictionary of Cancer Terms: fluorescence in situ hybridization
  2. National Cancer Institute. NCI Dictionary of Cancer Terms: chromosome
  3. National Cancer Institute. NCI Dictionary of Cancer Terms
  4. National Cancer Institute. Leukemia
  5. National Cancer Institute. NCI Dictionary of Cancer Terms: polymerase chain reaction
  6. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: karyotype
  7. National Cancer Institute. NCI Dictionary of Cancer Terms: complete blood count
  8. National Cancer Institute. NCI Dictionary of Cancer Terms: cytokine
  9. National Cancer Institute. Using Trusted Resources
  10. National Cancer Institute. NCI Dictionary of Cancer Terms: cure
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
Last updated: ← Back to the list

Open the interactive site →