The short answer
CPS is a scoring method used when tumour tissue is tested for the PD-L1 protein. Unlike a score that counts only cancer cells, CPS takes account of T-cells as well. It exists to help guide treatment choices for certain cancers.
CPS stands for combined positive score, and it is a way of reporting a PD-L1 result.
MedlinePlus describes CPS as measuring PD-L1 on both tumour cells and T-cells.
The tumour proportional score, or TPS, counts only the percentage of tumour cells with high PD-L1.
Because the two methods count different cells, their numbers are not interchangeable.
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The whole article, with every detail and caution.
This page is for people whose pathology report lists a combined positive score (CPS). It explains what CPS counts, how it differs from other PD-L1 scores, and what to ask your care team.
A scoring method, not a separate test
If your pathology report mentions a combined positive score, you have not had an extra test. You have had PD-L1 testing, reported in one particular way.
CPS is a counting method. It is one of a few the lab could use. Knowing which one applies to your sample matters more than knowing the raw number.
Ask what was counted before you try to work out how much was counted.
Why the counting method matters here
MedlinePlus lists the scoring systems used for PD-L1 results, and draws a clear line between them:
- The tumor proportional score measures the percent of tumor cells that have high amounts of PD-L1.
- The combined positive score measures PD-L1 on both tumor cells and T-cells.
That second part is the whole difference. T-cells are immune cells, and PD-L1 can show up on immune cells inside a tumor, not only on the cancer cells.
A method that ignores those immune cells and a method that counts them will not give the same number from the same slide. MedlinePlus describes them as two different scores.
Where PD-L1 fits at all
To make sense of any of these numbers, it helps to know what the protein does.
MedlinePlus explains that in healthy tissue, PD-L1 acts as an immune brake. It stops the immune system from attacking normal cells. Cancer can hijack that same signal: PD-L1 keeps your immune system from attacking cancer cells, letting tumors go unnoticed.
Testing for it asks whether that trick is happening. MedlinePlus states the practical purpose plainly: PD-L1 testing mostly helps your doctor decide on treatment options for certain cancers.
What a result may lead to
MedlinePlus describes the general pattern. Where PD-L1 is high, patients may benefit from immunotherapy. It names pembrolizumab, nivolumab and atezolizumab as common examples of such drugs. Where PD-L1 is low, MedlinePlus says immunotherapy likely will not help, and other approaches are needed.
None of that is stated as a sure thing, and those caveats come straight from the source, not from us softening it. MedlinePlus notes that immunotherapy can cause serious side effects in some people, and that not everyone benefits from it. That is why a doctor's judgment goes alongside the test result, not instead of it.
Why your number needs its own context
A number someone posts in an online group is a poor comparison, because the scoring method may differ. MedlinePlus says CPS and TPS count different cells. Your pathologist scored your own tissue with a specific method. Your care team can explain how it applies to your cancer.
Turning the number into a conversation
If you have a CPS on a report with no explanation attached, here is a short, useful sequence:
- Which scoring method is this, and why that one?
- What does this figure mean for the options I am considering?
- Does anything about my sample affect how the result should be read?
These questions can help you get a clear answer from your care team.
If the report has already been explained and you still feel lost
That is understandable. Ask for the explanation again, in writing if you can, or bring someone next time whose only job is taking notes. Understanding your own results is not a luxury. It is what lets you take part in decisions about your own care.
Common questions
Why did my report use CPS rather than TPS?
Your care team can tell you why this method was used for your sample. Asking which method was used, and why, is a good opening question.
Can I compare my CPS with someone else's PD-L1 number?
It is best not to. MedlinePlus describes CPS as measuring PD-L1 on both tumour cells and T-cells, while TPS measures the percentage of tumour cells with high amounts of the protein. Two numbers counting different things should not be compared.
Does a high CPS mean I will be offered immunotherapy?
It may support that conversation, but the decision rests on more than one figure. MedlinePlus notes that not everyone benefits from immunotherapy and that it can cause serious side effects in some people.
What are T-cells and why do they count?
T-cells are immune cells. The CPS method includes them because PD-L1 can appear on immune cells within a tumour as well as on the cancer cells themselves.
Questions to ask your doctor
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Sources last checked: 2026-10-02 what this meansLast updated: 2026-10-02Next planned review: 2027-08-11
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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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