Can a simple blood draw find breast cancer before a lump can be felt? A study published in Nature on November 11, 2026 brings that idea a step closer. Researchers at the Weizmann Institute of Science and the Hebrew University of Jerusalem, working with hospitals in Israel, the Mayo Clinic in Florida and teams in France, Germany, Italy and the United States, built an experimental breast cancer blood test that reads epigenetic marks, the chemical "switches" that control which genes are on or off. In stored blood samples, it told women with small, early-stage tumors apart from healthy women with about 95% accuracy, and it also flagged patients more likely to relapse. Here is what the test does, what it does not do yet, and which tests matter for you today.
What the new blood test looks for
When cells die, they release fragments of their DNA into the bloodstream. That DNA is not naked: it stays wrapped around small protein spools called nucleosomes, and those proteins carry chemical tags that reflect what the original cell was doing. A tumor leaves its own pattern of tags.
The team uses a technique developed in Efrat Shema's lab that lights up these tags with fluorescent antibodies and counts them one nucleosome at a time under a special microscope, across millions of nucleosomes from less than a milliliter of plasma. Artificial intelligence models then learn which combinations of tags point to cancer. Unlike most current liquid biopsies, the test does not look for DNA mutations: it looks at how genes are being switched on and off.
What the Nature study found
- Tumor tissue from 12 women operated on for breast cancer was analyzed first, cell by cell, to map its epigenetic diversity.
- The blood test was then applied to stored samples from 77 breast cancer patients followed for at least five years at the Mayo Clinic and from 30 healthy women. It separated early-stage cancers (tumors 2 cm or smaller, confined to the breast) from healthy controls with about 95% accuracy.
- According to the researchers, performance held regardless of breast density and across breast cancer types, in a larger set of 188 patient samples analyzed with Sheba and Kaplan medical centers.
- The team found a small group of aggressive "basal-like" cells hidden inside tumors that were not considered aggressive. Their epigenetic signature could be measured in blood, and the more of it a patient carried, the higher the risk that the cancer would come back. This signature separated patients who relapsed from those who stayed cancer-free with about 81% accuracy.
These numbers come from a laboratory comparison of known patients and healthy volunteers, not from screening thousands of women in the general population, where false alarms are more frequent. The test is not available to patients, and it has not been reviewed by the FDA.
How it compares with the tests used today
| Test | What it measures | Current role |
|---|---|---|
| Screening mammogram | X-ray image of the breast | Recommended every 2 years from age 40 to 74 (USPSTF) |
| CA 15-3 or CA 27.29 | Proteins released by some breast tumors | Follow-up of a known cancer, not screening |
| Circulating tumor DNA (ctDNA) | Tumor DNA mutations in blood | Treatment choice and recurrence monitoring in some patients |
| Epigenetic nucleosome test | Chemical tags on DNA spools in blood | Research only |
Dense breast tissue can hide tumors on a mammogram, and since September 2024 every U.S. mammography report must tell you whether your breasts are dense. A blood test that works regardless of density could one day complement imaging for these women. That is a hope, not yet a proven benefit.
What the study does not tell us yet
- The groups were small, and healthy controls were few.
- The samples were analyzed after the fact: no woman was screened with the test and then followed up.
- Results in women without symptoms, of different ages and backgrounds, are still unknown.
- Nobody knows yet whether finding cancer this way would save lives compared with mammography alone. The researchers themselves describe the test as experimental.
Which tests can monitor or screen for this?
For now, breast cancer screening relies on imaging. The U.S. Preventive Services Task Force recommends a mammogram every 2 years for women aged 40 to 74 at average risk. Women with a strong family history, a known gene variant or a prior chest radiation may be offered earlier screening or breast MRI.
Blood tests still play a role around a diagnosis:
- CA 15-3: helps follow a breast cancer already diagnosed; a normal value never rules out cancer. See also tumor markers explained.
- Circulating tumor DNA: used in some patients to watch for recurrence after treatment.
- Complete blood count and liver tests: checked before and during treatment.
- Multi-cancer blood tests: still being evaluated; read our analysis of the multi-cancer early detection trial.
Recent research advances
The Weizmann team had already shown, in a 2025 study, that the same single-molecule approach could recognize a rare childhood brain tumor from a few drops of plasma and track how it responded to treatment. The new Nature work moves the idea to breast cancer, the most common cancer in women, and adds something new: it does not only say "cancer or no cancer," it also gives a first clue about how aggressive a tumor is likely to be.
Other teams are testing different blood signals, such as small RNA molecules or fat-based compounds. A 2026 review pooling dozens of these studies found encouraging results but warned that most were small and compared known patients with healthy people. In plain terms: blood tests for breast cancer are progressing fast, but none can replace a mammogram yet. If you are offered a commercial "early cancer" blood test, ask your doctor what it has been validated for.
When to see a doctor
- A new lump in the breast or armpit, skin dimpling, redness, nipple changes or discharge: book a visit promptly, even if your last mammogram was normal.
- Your mammogram report says your breasts are dense: ask whether additional imaging makes sense for you.
- Several relatives with breast or ovarian cancer: ask about genetic counseling and a personalized screening plan.
- You are being treated or followed for breast cancer and your CA 15-3 is rising: discuss it with your oncology team rather than interpreting it alone.
Glossary
- Epigenetics: chemical marks that turn genes on or off without changing the DNA sequence itself.
- Nucleosome: a unit of DNA wrapped around a spool of proteins called histones; dying cells release them into the blood.
- Histone modification: a chemical tag added to the histone proteins, which changes how active nearby genes are.
- Liquid biopsy: a test that looks for traces of a tumor in a blood sample instead of a piece of tissue.
- Basal-like cells: cancer cells with aggressive features, more typical of hard-to-treat breast cancers.
- Dense breasts: breasts with more glandular and fibrous tissue than fat, which can hide tumors on a mammogram.
Frequently asked questions
Can a blood test detect breast cancer today?
Not reliably. No blood test is approved to screen for breast cancer. Mammography remains the reference screening test, and blood markers such as CA 15-3 are used to follow a cancer already diagnosed.
When will this epigenetic blood test be available?
No date has been announced. It must first be tested prospectively in large groups of women without symptoms, then reviewed by regulators.
Would it replace my mammogram?
No. Even if it is validated, the researchers present it as a possible complement to imaging, for example for women with dense breasts or to refine recurrence risk.
Does a normal CA 15-3 mean I do not have breast cancer?
No. CA 15-3 is often normal in early breast cancer and can be raised for other reasons, which is why it is not used for screening.
What is the difference with a ctDNA test?
A ctDNA test looks for tumor mutations in the DNA sequence. The new test reads the chemical tags carried by DNA spools, which reflect how cells behave.
Sources
- Furth N, Riemenschneider C, Arieli Y, et al. Epigenetic heterogeneity in breast tumours informs diagnosis and prognosis. Nature. 2026. DOI: 10.1038/s41586-026-11230-y
- Medical Xpress. Experimental blood test detects early breast cancer and predicts recurrence. November 2026
- The Times of Israel. Israeli blood test detects early breast cancer with 95% accuracy. November 2026
- Erez N, Furth N, Fedyuk V, et al. Single-molecule systems for the detection and monitoring of plasma-circulating nucleosomes and oncoproteins in diffuse midline glioma. Cell Rep Med. 2025;6(1):101918. DOI: 10.1016/j.xcrm.2024.101918
- Arafat HM, Ali A, Tengku Din TADAA, et al. Diagnostic accuracy of circulating microRNAs and lipidomic biomarkers for early breast cancer detection: a systematic review and meta-analysis. PLoS One. 2026;21(7):e0354728. DOI: 10.1371/journal.pone.0354728
- US Preventive Services Task Force. Screening for Breast Cancer: Recommendation Statement. JAMA. 2024;331(22):1918-1930. DOI: 10.1001/jama.2024.5534
- U.S. Preventive Services Task Force. Breast Cancer: Screening. April 2024
- National Cancer Institute. Tumor Markers in Common Use
- National Cancer Institute. Dense Breasts: Answers to Commonly Asked Questions
- U.S. Food and Drug Administration. Mammography: What You Need to Know
Further reading
- Breast cancer: symptoms, diagnosis and treatment
- Breast cancer screening guidelines in 2026
- Breast cancer recurrence blood test: the ctDNA study
- Forever chemicals and aggressive breast cancer
- Tumor antigen CA 15-3 explained
- Multi-cancer early detection test: what the trial showed
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