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Breast marker reports

Can Marker Results Change — Between Biopsy and Surgery?

It is possible for your ER, PR or HER2 result from a biopsy to differ from the result on the tissue removed at surgery. This is called discordance, and your oncologist will explain which result is being used to guide your care.

Medically reviewed by Dr. Bharati Devi Gorantla, Medical Oncologist, MBBS · MD · DM (Adyar, Chennai) · ECMO · MRCP SCE (UK) · Last reviewed September 2026

  • Discordance is real — Marker results do not always match between the core biopsy and the surgical specimen.
  • Biology varies within a tumour — Different parts of the same tumour can have different receptor levels, so two samples from different areas may give different readings.
  • Treatment before surgery matters — Therapy given before your operation can change the tumour's biology before the surgical specimen is tested.
  • Your team reviews both results — Your oncologist considers both samples together and explains which result will guide your treatment plan.
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Yes, ER, PR and HER2 results can differ between a core biopsy and the surgical specimen tested after your operation. This is called discordance, and it happens in a minority of cases. Your oncologist will consider both results and explain which one will guide your treatment.

Do breast marker results actually change between biopsy and surgery?

Yes, and it is more common than many people expect. The tissue sampled at biopsy and the tissue removed at surgery do not always give identical marker results.

The main reason is that breast cancers are not always uniform throughout. Different areas of the same tumour can show different levels of hormone receptors or HER2 expression. A core biopsy samples one area, and the surgical specimen represents a larger and sometimes different part of the mass.

Treatment given before surgery — called neoadjuvant therapy — adds a second cause. It can change the tumour's biology, so the surgical specimen may genuinely reflect a different state rather than simply sampling a different area.

Terms your report may use

Discordance
When the marker result from your biopsy and the result from your surgical specimen do not match.
Concordance
When both samples give the same result — this is the more common situation.
Tumour heterogeneity
Natural variation within a single tumour. Different cells in different parts of the mass can behave differently, which is why two samples from the same tumour can sometimes give different results.
Neoadjuvant therapy
Treatment — chemotherapy, hormone therapy or targeted therapy — given before surgery. It can alter the tumour's biology before the surgical specimen is tested.
Surgical specimen
The tissue removed during your operation. It is usually sent to the laboratory and tested for the same markers as your original biopsy, which is how discordance is detected.
Reflex ISH testing
A second laboratory method used when an initial HER2 result is borderline or conflicts with a previous result. ASCO and CAP guidelines recommend it in these situations to determine HER2 status more precisely.

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Which result is used, and for which marker?

MarkerStability between samplesApproach when results differ
ER (oestrogen receptor)Generally stableBoth results reviewed; the larger surgical sample usually carries more weight, with clinical context deciding
PR (progesterone receptor)Generally stable; less predictive than ER aloneTreated similarly to ER; oncologist weighs both results together
HER2More prone to variation between tumour areasReflex ISH testing recommended by ASCO and CAP when results are borderline or discordant between samples
Ki-67Most variable; changes readily after treatmentSurgical specimen result is generally preferred when neoadjuvant therapy was given before surgery

Questions families often ask at this point

Which result — biopsy or surgery — will actually be used for my treatment?

This depends on your specific situation. When no treatment was given before surgery, the surgical specimen result is often given more weight because it comes from a larger and more representative sample. When treatment was given before surgery, your oncologist will consider both results alongside how the tumour responded to that treatment. There is no single rule that applies to every patient; your team will explain their reasoning if you ask.

Should I be worried if the two results are different?

Not automatically. Discordance does not mean something went wrong with your care or that your prognosis has changed. It is a recognised phenomenon that oncologists and pathologists are trained to manage. What matters is that your treating team is aware of both results and has a clear rationale for which one is guiding your plan. If you are unsure whether both results have been seen and considered together, ask directly at your next appointment.

What happens if my HER2 status changes from positive to negative, or the other way?

A change in HER2 status between biopsy and surgery is taken seriously because HER2 is one of the key factors in treatment planning. When this happens, ASCO and CAP guidelines recommend additional testing — usually reflex ISH testing — to clarify the true status before a final treatment decision is made. Your oncologist will not act on a single discordant HER2 result without first confirming it through the appropriate pathway.

Could the laboratory have made an error?

Laboratory error is possible but uncommon in accredited centres that follow standard testing protocols. When two results differ, the more frequent explanation is genuine biological variation within the tumour, a sampling effect, or a change caused by treatment before surgery. If you have concerns about testing reliability, ask your oncologist whether the result was confirmed by a second method or whether a second opinion on the pathology slides has been considered.

Do I need a new biopsy if my results are discordant?

Not necessarily. The surgical specimen is usually sufficient to clarify the picture, and additional testing such as reflex ISH can be performed on the existing tissue without a new procedure. A new biopsy is more relevant when the question involves a recurrence or a site of disease not sampled during the original surgery. Your oncologist will tell you whether further tissue is needed in your specific case.

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Common questions

Frequently asked questions

Why do marker results sometimes change between biopsy and surgery?

Two things can cause this. First, a breast tumour is not always biologically uniform — different areas can show different levels of hormone receptors or HER2, so two samples from different parts give different readings. Second, treatment given before surgery can genuinely change the tumour's biology, so the surgical specimen may reflect a different state than the original biopsy did. Both are recognised causes of discordance, not signs of error.

Which result determines my treatment — the biopsy or the surgery?

Usually the surgical specimen carries more weight because it comes from a larger and more representative piece of tissue. When treatment was given before surgery, both results are considered together alongside how the tumour responded. Your oncologist will tell you which result is being used and why. If that is not clear from your consultation, it is a reasonable question to ask directly.

My ER result changed between biopsy and surgery. What does that mean?

A change in ER status — particularly from positive to negative after treatment before surgery — can reflect a genuine biological response to that treatment. Your oncologist will review both results in the context of what treatment you received and what the surgical specimen showed overall. This affects planning decisions, which is why both results are recorded and not just the most recent one. Ask your team to walk you through what the change means for your specific situation.

Is HER2 discordance more common than ER or PR discordance?

Yes. HER2 status can vary more across different areas of a tumour than hormone receptor status, which tends to be more uniform. This is why ASCO and CAP guidelines include specific guidance on how to handle borderline or conflicting HER2 results, including reflex ISH testing to clarify. ER and PR are generally more stable between samples, though changes do occur, particularly after treatment before surgery.

Does discordance mean I need to repeat all my marker testing?

Not routinely. The surgical specimen is usually tested for all markers as part of standard pathology, so you already have two sets of results. When a specific result is borderline or contradicts the biopsy finding, additional testing — such as ISH for HER2 — can be done on the existing tissue. Your oncologist will recommend further testing only when it would change or clarify the treatment decision, not as a default for every discordant result.

Should I get a second opinion on the pathology if my results changed?

A second opinion on pathology is always reasonable when a result is uncertain or would significantly affect your treatment plan. This is particularly relevant for borderline HER2 results, where the difference between positive and negative has clear treatment implications. You can ask your oncologist to refer your slides to a specialist pathology centre for review. This is a normal part of good cancer care and not a sign of distrust toward your team.

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What Is a Biopsy?

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Preparing for a Biopsy

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Recovery and Aftercare

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Biopsy by Body Part

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