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Ki-67 Nuclear Antigen Expression in Breast Cancer Tissue

Published: August 9, 2026Updated: August 16, 2026

This test measures the presence of Ki-67, a protein found in actively dividing cells, specifically in breast cancer tissue samples. It helps assess how quickly cancer cells are growing.

Quick summary

["Ki-67 helps doctors understand how fast your breast cancer cells are multiplying, guiding treatment decisions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
85330-9
Short code
Ki-67 nuclear Ag NFr Br ca spec ImStn
Synonyms
Ki-67 nuclear Ag NFr Br ca spec ImStn
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immune-stain
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test if you have breast cancer to evaluate the rate of cell division in your tumor. High levels of Ki-67 often suggest more aggressive cancer that may require stronger treatment.

How Is the Sample Collected?

A small sample of your breast cancer tissue is taken during surgery or a biopsy. This sample is then examined under a microscope to detect Ki-67 protein.

What Does the Result Mean?

Results are typically reported as a percentage, indicating the proportion of cancer cells expressing Ki-67. A higher percentage suggests faster cell growth, which may influence treatment options like chemotherapy or targeted therapies.

Common Uses and Considerations

This test is most useful in planning treatment for newly diagnosed breast cancer. It helps doctors decide whether to use treatments that target rapidly dividing cells, such as chemotherapy or hormonal therapy.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

A higher Ki-67 level may mean your cancer is more likely to grow quickly, which can affect your treatment plan. Your doctor will discuss the results with you in detail to tailor your care.

Short name

Ki-67 Breast Cancer Proliferation Marker

Frequently asked questions

What if I Have Questions About My Results?
If your test shows a high Ki-67 level, ask your doctor about whether this means you’ll need additional treatments like chemotherapy or if other options are available.
How Does This Test Compare to Other Tests?
Ki-67 is often used alongside other tests, such as estrogen or HER2 receptor status, to create a full picture of your cancer’s behavior and guide treatment choices.
Will This Test Affect My Treatment Plan?
Yes, your doctor will use Ki-67 results along with other factors to decide on the best treatment options for you, such as whether to start chemotherapy sooner or adjust hormone therapy.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy