The short answer
Clonal hematopoiesis means one family of blood-forming cells carries an acquired gene change and has grown larger than its neighbors. It is linked to aging. It is not a cancer, and published follow-up puts the rate of progression to a blood cancer at roughly 0.5 to 1 percent per year.
It describes a clone of blood-forming cells, not a tumor and not a diagnosis of leukemia.
It is acquired during aging, and most people who acquire it will never develop MDS.
Published estimates put progression to a blood cancer at about 0.5 to 1 percent per year, similar to MGUS.
It can put a mutation into a blood-based tumor test that never came from the tumor.
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This page is for anyone whose blood test or tumor DNA report mentions clonal hematopoiesis, CHIP, or CCUS. It explains what these terms mean, how common they are, and what the risk actually looks like.
A clone is not a tumor
Your blood cells all come from stem cells in the bone marrow, the soft tissue inside bones where blood is made. Over a lifetime, those stem cells pick up small DNA changes. Most changes do nothing.
Occasionally one gives a stem cell a slight edge. Its descendants grow to make up more of your blood than they should. That family of related cells is the clone. Hematopoiesis means blood-cell making, so clonal hematopoiesis means one clone making a growing share of your blood.
There is no lump, no mass, and often nothing wrong with your blood counts. The finding is in your DNA, not something that shows up as a growth.
It is linked to aging
The 2015 review describes people who acquire clonal hematopoiesis during aging. DNA sequencing can now detect these small clones. Many people who have one will stay well and die of other causes.
CHIP, CCUS, and the space between them
The word on your report may be one of several, and they are not interchangeable.
- CHIP means clonal hematopoiesis of indeterminate potential. A clone is present, blood counts are normal, and the marrow does not show the cell changes that define myelodysplastic syndromes (MDS), a group of disorders where the marrow makes too few healthy blood cells.
- CCUS means clonal cytopenias of undetermined significance. Cytopenia means a low blood count. A clone is present alongside a genuinely low count, but without enough evidence for an MDS diagnosis.
- MDS itself is a diagnosis, defined by low counts, abnormal cell shapes and clonal growth together.
The 2015 review that introduced the term CHIP compared it to MGUS and to monoclonal B-cell lymphocytosis. Those are precursor states that are usually benign and usually do not progress.
What the follow-up data actually showed
Two things are true at once, and both belong on the page.
The clone is a real risk factor. It is associated with a higher chance of a later blood cancer. It is also linked to higher death rates from any cause, probably through heart and blood vessel disease.
The absolute yearly risk stays small. The review that named CHIP put the rate of progression to a blood cancer at roughly 0.5 to 1 percent per year, and noted the risk appears proportional to the size of the clone. Its authors state plainly that most people who acquire clonal hematopoiesis with age will never develop MDS.
That is why the size of your clone is worth asking about.
When it is an artifact of a liquid biopsy
This is the version most cancer patients meet, and it is easy to misread.
Some tumor tests read DNA fragments in the blood. A blood cell clone could add a change that did not come from the tumor. Ask your team whether the result was checked against a blood sample, so changes from blood cells can be told apart.
What hematology follow-up looks like
Ask your care team how often to repeat blood counts and whether you need a hematology visit.
A low count changes the conversation, because that is what separates CHIP from CCUS. Lab Tests for Cancer explains what a blood count measures. Biomarker Testing and Precision Medicine explains how tumor DNA tests are used.
Sources
Common questions
Is clonal hematopoiesis a type of cancer?
No. CHIP is defined as an acquired mutation that drives clonal growth without low blood counts and without the abnormal cell shapes that define myelodysplastic syndromes. The authors of that definition note that most people who acquire clonal hematopoiesis with age will never develop MDS.
How likely is it to turn into leukemia?
The review that named CHIP put the rate of progression at roughly 0.5 to 1 percent per year, comparable to MGUS and monoclonal B-cell lymphocytosis. Risk appears to scale with the size of the clone, so ask what fraction of cells carried the change.
Why did this show up on my tumor test?
Blood-based tumor tests read DNA floating in plasma, and some of it comes from blood cells rather than the tumor. Ask whether your team checked a blood sample alongside the tumor test to tell the two apart.
What is CCUS?
Clonal cytopenias of undetermined significance. It describes a clone found alongside a genuinely low blood count, but without enough other features to call it MDS. It sits between CHIP and a diagnosis, and it is a hematology conversation.
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Sources last checked: 2026-10-02 what this meansLast updated: 2026-10-02Next planned review: 2027-08-09
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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