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Breast cancer markers

HER2 Scores: 0, 1+, 2+ and 3+ — What Equivocal Actually Means

A HER2 score of 2+ on your pathology report is not a positive or negative result — it is an inconclusive one. That word, equivocal, means a second test is needed before your oncologist can make any decision about treatment.

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

  • 2+ is not a verdict — Equivocal means the staining test could not give a clear answer, not that you are HER2-positive.
  • A second test decides — FISH testing looks directly at the HER2 gene and returns a clear positive or negative result.
  • 0 and 1+ are both negative — These two scores mean no significant HER2 protein was found. No further HER2 testing is needed at diagnosis.
  • 3+ is clearly positive — Strong, uniform staining across the sample. Your oncologist will explain what that means for your treatment plan.
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A HER2 score of 2+ is called equivocal, which means the standard staining test could not give a clear answer. It does not mean HER2-positive or negative — it means a second, more precise test called FISH is needed before your oncologist can decide on treatment. Scores of 0 and 1+ are negative; 3+ is positive.

What does each HER2 score mean?

HER2 is a protein found on the outer surface of breast cancer cells. The IHC test measures how much of that protein is present and gives a score from 0 to 3+.

Scores of 0 and 1+ mean the protein is absent or barely detectable. Both are called HER2-negative, and no further HER2 testing is needed at diagnosis. A score of 3+ means the protein is strongly and uniformly present across the sample, and that result is called HER2-positive.

A score of 2+ sits between those two extremes. The protein was detected, but not clearly enough to call it positive or negative. That is what equivocal means. The test does not stop there — a second test is required.

What should you do next after a 2+ result?

  • Ask your oncologist or pathology coordinator when the FISH test will be ordered — it should follow automatically from a 2+ IHC result.
  • Keep a printed copy of both your IHC report and your FISH report for your records.
  • Do not assume you are HER2-positive while waiting for FISH — the result could go either way.
  • Write down your questions before your next appointment so you do not forget them in the consultation room.
  • Tell your care team about any supplements or herbal medicines you are taking before further tests are done.

What do the words on your HER2 report mean?

HER2
Human Epidermal Growth Factor Receptor 2. A protein on the surface of cells. When it is overexpressed in cancer cells, it signals those cells to divide faster than normal.
IHC (immunohistochemistry)
The standard staining test that measures how much HER2 protein sits on the surface of cancer cells. It produces a score of 0, 1+, 2+ or 3+, and it is done on the biopsy sample you have already had.
Equivocal
Uncertain or inconclusive. Used when an IHC score is 2+, meaning the protein level was neither clearly high nor clearly low. It is not a diagnosis — it is a signal that more information is needed before a decision can be made.
FISH (fluorescence in situ hybridization)
A gene-level test that counts the actual copies of the HER2 gene inside the cancer cells. Unlike IHC, it gives a definitive positive or negative result and can be done on the same biopsy tissue.
Gene amplification
When a cancer cell contains extra copies of a gene. HER2-positive cancers typically have many more copies of the HER2 gene than a normal cell would, and FISH is the test that measures this directly.

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How do the four HER2 scores compare?

ScoreIHC resultWhat it meansNext step
0NegativeNo HER2 protein detected on the cell surfaceNo further HER2 testing needed at diagnosis
1+NegativeVery faint protein present; not considered significantNo further HER2 testing needed at diagnosis
2+EquivocalProtein detected but the level is ambiguous — inconclusiveFISH or ISH test required to give a definitive result
3+PositiveStrong, uniform protein expression across the sampleDiscuss HER2-targeted treatment options with your oncologist

Did you know?

Around one in five breast cancers is HER2-positive. Among tumours that score 2+ on IHC, a meaningful proportion are ultimately confirmed HER2-positive when FISH testing is completed — which is exactly why ASCO and CAP guidelines treat FISH as a required step after a 2+ result, not an optional one.

Source: ASCO/CAP HER2 Testing Guidelines

What do families most often ask about HER2 reports?

Does a 2+ score mean my cancer is more aggressive?

No. The 2+ score says something about the test result, not about how the cancer behaves. Equivocal means the staining test was not precise enough to decide HER2 status — it tells you nothing about the grade of your cancer or how quickly it is growing. Grade and HER2 status are separate items on your pathology report. Your oncologist will explain what each part of the report means for your specific case.

Will I need a new biopsy for FISH testing?

In most cases, no. FISH is performed on the same tissue sample from the biopsy you have already had. The laboratory stores sections of the biopsy block for exactly this purpose. A new biopsy is only needed if the original sample was too small, damaged, or otherwise insufficient for FISH. Ask your pathology coordinator whether the existing block is being used, so you are not waiting unnecessarily for a procedure that may not be required.

How long does FISH testing take?

FISH is more complex than IHC and typically takes longer. Turnaround times vary between laboratories. Your oncologist or pathology coordinator can give you an estimated date when FISH is ordered. If you have not heard back within the timeframe you were told, it is entirely reasonable to call and ask for an update. Knowing where you are in the process reduces unnecessary worry while you wait.

What happens if my FISH result is negative?

A negative FISH result means your cancer is HER2-negative, even though the IHC came back as 2+. Your treatment plan will be based on your other markers — ER, PR, Ki-67, and stage — rather than HER2-targeted approaches. Being HER2-negative does not mean you are out of options; it means the treatment plan is matched to the biology your cancer actually has. Your oncologist will explain what the full set of markers means together.

What happens if my FISH result is positive?

A positive FISH result confirms that your cancer is HER2-positive. Your oncologist will use that, alongside your stage and other results, to plan your treatment. What that plan looks like depends on whether you are early stage or locally advanced, and on the sequence of surgery and other treatments being considered. Your oncologist will explain the options that apply to your specific situation — the FISH result is a key input, not the only one.

Can a HER2 result change between the biopsy and surgery?

It can. Some oncologists request that HER2 testing is repeated on the surgical specimen if the biopsy result was equivocal, or if treatment was given before surgery. Tumours are not always uniform throughout, and different areas of the same cancer can show different characteristics. If you have had treatment before surgery, ask your oncologist whether the surgical sample will also be tested and what would change if the result differed from the original.

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Common questions

Frequently asked questions

My report says HER2 2+. Am I HER2-positive?

Not yet known — that is the honest answer. A score of 2+ is equivocal, meaning the staining test could not decide. You are neither confirmed positive nor confirmed negative until FISH testing is completed. FISH looks at the HER2 gene directly and gives a clear result. Until that comes back, your HER2 status is genuinely undecided, and treatment decisions that depend on it cannot be finalised.

What is the difference between IHC and FISH?

IHC measures how much HER2 protein sits on the surface of cancer cells, using a staining dye. It is fast and is always done first, but it cannot reliably distinguish borderline protein levels. FISH goes deeper — it counts the actual copies of the HER2 gene inside the cell. Because gene amplification is a more fundamental measurement, FISH is the definitive test when IHC gives an inconclusive 2+ result. In most cases both tests use the same biopsy tissue.

Is a HER2 score of 1+ the same as 2+?

No, and the difference matters. A score of 1+ is HER2-negative — faint protein is detectable but not at a level considered significant, and no further HER2 testing is needed at diagnosis. A score of 2+ is equivocal — the protein level is ambiguous, and FISH is required to resolve it. The two are not on a spectrum of positivity: 1+ is a concluded negative result, while 2+ is an open question that still needs an answer.

Do all laboratories interpret HER2 scores the same way?

Reputable laboratories follow ASCO/CAP HER2 testing guidelines, which standardise how scores are assigned and when FISH must follow. There can be variation on borderline cases, which is one reason a second opinion on the pathology — sending the slides to another laboratory — is sometimes worth requesting, particularly for a 2+ result. Ask your oncologist whether a second read is appropriate in your situation before assuming the first reading is definitive.

My relative was HER2-positive. Will my treatment be the same?

Unlikely to be identical. HER2 status is one factor, but treatment plans are shaped by the full picture — your cancer's stage, ER and PR status, Ki-67 score, general health, and decisions about surgery sequence. Two people who are both HER2-positive can end up on different plans because the rest of their results differ. The most reliable information about your plan comes from your own oncologist, who has your complete report in front of them.

What should I ask my oncologist about my HER2 result?

Ask three things: what exactly my IHC score means for next steps; when FISH will be ordered and how long the result takes; and once FISH is back, what that result means for my treatment plan. It is entirely reasonable to ask for your reports in writing. If the full plan cannot be finalised until FISH returns, ask what will be decided at that next appointment so you can prepare the right questions in advance.

Full index

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What Is a Biopsy?

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Types of Biopsy Compared

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Preparing for a Biopsy

What to Expect on the Day of Your Biopsy →

Recovery and Aftercare

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Biopsy by Body Part

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Understanding Your Report

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IHC and Molecular Markers

IHC and Molecular Markers on a Biopsy: What They Mean →

Grading and Scoring Systems

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How Accurate Is a Biopsy?

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