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Ki-67 and the proliferation index in lymphoma | CION Cancer Clinics
Ki-67 is the percentage of lymphoma cells that were dividing when your biopsy was taken. A high figure means the lymphoma is growing fast and usually needs treatment soon; a low figure means it is growing slowly. It is not a survival figure and not a stage. What it means depends on the type of lymphoma, which this page explains type by type. At CION Cancer Clinics, our haematology team plans myeloma and lymphoma care with you, discussed at a tumour board and explained in plain words.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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The short answer
What does Ki-67 mean on a lymphoma report?
Ki-67 is the share of lymphoma cells that were dividing when the biopsy was taken. A high Ki-67 means the lymphoma is growing quickly, and a low Ki-67 means it is growing slowly. It is written as a percentage, and it is one clue among many, not a verdict.
How the number is measured
Ki-67 is a protein found only in cells that are in the middle of dividing. The laboratory stains the tissue with an antibody that sticks to it, so dividing cells turn brown. The pathologist, the doctor who reads tissue, then estimates what proportion of the lymphoma cells are stained. This is part of immunohistochemistry, the staining test that also shows markers such as CD20.
Why the same word can mean different things
Fast-growing lymphomas are often called aggressive, and slow-growing ones indolent. These words sound frightening or comforting, but they describe speed, not outcome. Many fast-growing lymphomas respond well to treatment precisely because dividing cells are more sensitive to it. Many slow-growing ones stay quiet for years, yet are harder to clear completely.
Ki-67 is estimated by eye or by software, and two laboratories can report slightly different figures from the same tissue.By lymphoma type
How is Ki-67 read in different lymphomas?
The same figure means different things in different subtypes. It is always read against the name of the lymphoma.
Diffuse large B-cell lymphoma
Ki-67 is usually high, because this is a fast-growing lymphoma by nature. A high figure here is expected and does not, on its own, change the treatment plan.
Follicular lymphoma
Ki-67 is usually low. A figure that is higher than expected may make the pathologist look again for areas that have turned into a faster type, which can change the plan.
Your report may also mention
- Grade, based on the number of large cells
- Transformation, if a faster type is found
Mantle cell lymphoma
Here Ki-67 carries extra weight. It is one of the factors used to place a person in a lower-risk or higher-risk group, and it can guide how intensive treatment should be.
Burkitt lymphoma
Almost every cell is dividing, so Ki-67 is close to the top of the scale. This helps the pathologist confirm the diagnosis, alongside gene tests, and it signals that treatment should begin promptly.
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What does a high or low Ki-67 usually suggest?
A higher Ki-67
A lower Ki-67
More cells are dividing, so the lymphoma is growing faster
Fewer cells are dividing, so it is growing more slowly
Symptoms may appear or change over weeks
Symptoms, if any, often change over months or longer
Treatment usually starts soon after staging
Some people are watched closely before any treatment
Often responds quickly to chemotherapy
May respond more slowly and can return later
Commonly believed
What do families often misread about Ki-67?
"The Ki-67 percentage is the chance of survival."
It is not a survival figure in any form. It measures how many cells were dividing in one small piece of tissue. Outlook depends on the subtype, stage, blood tests and your general health, read together by your haematologist.
"A high Ki-67 means nothing can be done."
The opposite is often true. Fast-growing lymphomas are usually treated straight away, and many respond well because dividing cells are more easily damaged by treatment. Speed tells your team how soon to act.
"A low Ki-67 means we can ignore it."
A slow lymphoma still needs a haematologist and regular review. Some people are watched rather than treated at first, but that is a planned decision with check-ups, not a reason to stop follow-up.
"If the figure changes on a new biopsy, the first lab was wrong."
Ki-67 can differ between parts of the same node and between laboratories. A clear rise on a later biopsy can also be real, and your team will want to know why.
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After the report
What happens after the Ki-67 result comes back?
The full diagnosis is confirmed
Ki-67 is read with the other markers and the shape of the cells. The final diagnosis line names the lymphoma, and that name matters more than any one figure on the page.
Staging tests are arranged
Scans, usually a PET-CT, show where the lymphoma is in the body. Blood tests such as LDH are added. Sometimes a bone marrow test is needed as well.
The case is discussed
At CION, the haematology team presents the biopsy, scans and blood results at a tumour board, where several specialists agree on the plan together rather than one doctor deciding alone.
The plan is explained to you
You hear whether treatment should start now or whether close watching is safer, and why. Bring the family member who will help with decisions, and your written questions.
Being straight with you
What can Ki-67 not tell you?
Ki-67 cannot tell you the stage of the lymphoma, which is how far it has spread. It cannot tell you which treatment will work, and it cannot predict how long treatment will take. A single percentage from one small sample does not describe the whole lymphoma.
Why there is no universal cut-off
You may read online that a certain percentage is "high". Cut-offs vary between lymphoma types, between studies and between laboratories. A figure that is ordinary in one subtype can be unusual in another. That is why this page gives no single number to compare your report with.
Questions worth asking your haematologist
Ask whether the Ki-67 is what you would expect for this subtype. Ask whether it changes the plan or the timing. Ask whether any area of the biopsy looked faster-growing than the rest. These questions turn a number into something you can act on.
If the report has been in your hand for days without an appointment, call the helpline rather than waiting and searching alone.
Did you know
The wax block from your biopsy is kept by the laboratory. If Ki-67 or another marker needs checking again, it can often be re-stained or sent for a second review without a new biopsy.
Questions we are asked
Common questions about Ki-67 in lymphoma
Is a high Ki-67 always bad news?
No. It means the lymphoma is growing fast, which usually means treatment starts soon. In several fast-growing lymphomas, treatment is planned with the aim of clearing the disease completely. What a high figure means for you depends on the subtype and stage, so ask your haematologist to explain it for your own case.
Can Ki-67 go down with treatment?
Ki-67 is measured on a biopsy, not on a blood test, so it is not tracked during treatment. Response is checked with scans and your symptoms instead. A new biopsy is usually done only if the lymphoma seems to come back or behaves unexpectedly.
Why does my report give a range instead of one number?
Some parts of a lymph node have more dividing cells than others, and Ki-67 is estimated rather than counted cell by cell. A range is an honest way of reporting that. Your haematologist reads the range together with the subtype, so a range is not a sign of a poor report.
Is Ki-67 the same as the grade?
They are related but not the same. Grade, used in follicular lymphoma, is based on how many large cells are seen. Ki-67 measures how many cells are dividing. Both describe how active the lymphoma is, and your report may give both.
Do we need a second opinion on Ki-67?
Not usually for Ki-67 alone. A second review of the slides is worth asking about when the subtype itself is uncertain, when the figure does not fit the diagnosis, or when the plan hinges on it, as it can in mantle cell lymphoma. The existing block can be reviewed.
Can diet or supplements lower Ki-67?
There is no good evidence that any food or supplement changes Ki-67 in lymphoma. Some supplements can interfere with chemotherapy or the liver. Tell your haematologist about anything you are taking, and eat enough to keep your weight steady during treatment.
Does Ki-67 decide whether chemotherapy is needed?
Rarely on its own. The decision rests mainly on the type of lymphoma, the stage, symptoms and blood results. Ki-67 adds detail, and in a few subtypes it influences how intensive treatment should be. The treating team weighs it with everything else.
Who can explain our report properly?
A haematologist or medical oncologist who treats lymphoma, with the full biopsy report and scans in front of them. CION's haematology team can read the report with you, explain each figure and tell you what the next step is. Bring every report you have, including older ones.
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Sources
- National Cancer Institute — Adult Non-Hodgkin Lymphoma Treatment (PDQ)
- National Cancer Institute — Tumor Grade
- Cancer Research UK — Non-Hodgkin lymphoma
- Leukemia & Lymphoma Society — Non-Hodgkin Lymphoma
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
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