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Medical glossary

Blast

A blast is an immature, “young” blood cell. Normally there are few in the bone marrow, and they develop into mature cells.

Last updated: ~1 min read
A large immature blast cell with a big nucleus among red blood cells in a blood smear
Figure 1.A blast: an immature cell with a large nucleus

01Short answer

In acute leukaemia, blasts multiply without maturing, fill the bone marrow and can spill into the blood. For diagnosis and to judge treatment, the percentage of blasts in the marrow and blood is measured. In remission, the share of blasts falls to a normal level. The type of blast (myeloid or lymphoid) helps identify the type of leukaemia.

02Simple explanation

A young cell.

Normally few.

Many in leukaemia.

The percentage is measured.

03Scientific explanation

NCI: a blast is an immature blood cell.

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

04What happens in the body?

Where it is measured

Blood tests and bone marrow aspiration.

Crowding
Figure 2.Illustration: Crowding

What it means

The percentage shows the effect of treatment.

A maturation ladder
Figure 3.A maturation ladder.

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
Where it is measuredBlood tests and bone marrow aspiration.
What it meansThe percentage shows the effect of treatment.
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

Maturation
A cell becoming its mature form.
Blast percentage
The share of blasts among all cells.
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

Blasts were found in my blood: is it leukaemia?

Not always; further tests are needed.

Are there no blasts in remission?

There may be a few, but within the normal range.

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. Blasts were found in my blood: is it leukaemia?

  2. Are there no blasts in remission?

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

My questions

12Sources

  1. National Cancer Institute. NCI Dictionary of Cancer Terms: blast
  2. National Cancer Institute. Leukemia
  3. National Cancer Institute. Adult Acute Myeloid Leukemia Treatment (PDQ®) – Patient Version
  4. National Cancer Institute. NCI Dictionary of Cancer Terms
  5. National Cancer Institute (NCI). NCI Dictionary of Cancer Terms: stem cell transplant
  6. American Cancer Society. Low Blood Counts
  7. National Cancer Institute. NCI Dictionary of Cancer Terms: biopsy
  8. National Cancer Institute. NCI Dictionary of Cancer Terms: chromosome
  9. National Cancer Institute. NCI Dictionary of Cancer Terms: karyotyping
  10. National Cancer Institute. NCI Dictionary of Cancer Terms: cytogenetics
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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