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Understanding your biopsy report

IHC and Molecular Markers — What Your Biopsy Report Is Telling You

When your biopsy report comes back covered in abbreviations and numbers, it can feel like a foreign language. This page explains what IHC and molecular markers are, which ones appear most often, and why the results matter for your treatment.

Medically reviewed by Dr. T. Raghavender Reddy, Medical Oncologist, MBBS · DM (Medical Oncology) · MD (Radiation Oncology) · Last reviewed September 2026

  • Proteins, not just a cancer type — IHC and molecular tests look at the specific biology of your tumour, not just which organ it is in.
  • Not every marker is tested every time — The pathologist orders tests based on your cancer type, so your report will not include every marker that exists.
  • Scores are not a verdict — Numbers like 3+ or percentages describe what the laboratory found. Your oncologist explains what they mean for your care.
  • The two tests work together — IHC looks at proteins on cells. Molecular testing reads the DNA inside. Together they build a more complete picture.
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IHC, or immunohistochemistry, is a laboratory test done on your biopsy tissue. It uses chemical stains to detect specific proteins on cancer cells. The results — alongside those from molecular tests — tell your oncologist what is driving the tumour and which treatments are most likely to work for your specific cancer.

What does IHC mean on a biopsy report?

IHC stands for immunohistochemistry. The laboratory takes a thin slice of your biopsy tissue, applies chemical stains, and examines it under a microscope. The stains attach to specific proteins on the cancer cells, making those proteins visible.

The result tells the pathologist what proteins the tumour is producing — a lot, a little, or none at all. Each protein is a clue about how the cancer cells are behaving and what is keeping them growing.

The score or label next to each marker — words like positive, negative, 3+, or high — is the pathologist's reading of that stain. It is information, not a verdict. Your oncologist uses it alongside your cancer type and stage to decide what to do next.

Which markers appear most often on a biopsy report?

Not every marker is tested on every biopsy. The pathologist orders tests based on your cancer type. The most common ones fall into a few categories.

Hormone receptors — ER and PR — appear mainly on breast cancer reports and some other cancers. They show whether the tumour is being driven by oestrogen or progesterone. Ki-67 is a proliferation marker that indicates how rapidly the cancer cells are dividing.

HER2 is a protein on the surface of some cancer cells that signals them to grow. It is tested in breast and stomach cancers among others, and the result is usually reported as negative, 1+, 2+, or 3+.

PD-L1 is a protein that some tumours use to evade immune detection. MMR, or mismatch repair, indicates whether cancer cells have a functioning DNA repair system. Your oncologist will explain which of these apply to your cancer type and what each result means for your care.

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What does molecular testing add that IHC cannot show?

IHC reads proteins on the surface of cells. Molecular testing goes deeper — it sequences the DNA or RNA inside the cancer cells to find specific mutations, gene rearrangements, or copy number changes that staining alone cannot detect.

Some gene changes only show up at the DNA level. A molecular test can find a mutation in a growth-driving gene even when the protein that gene produces looks normal under IHC staining. This matters because certain mutations change which treatments are most likely to be effective.

Microsatellite instability, or MSI, is one example where both approaches can be used: IHC screens for it by looking at specific repair proteins, and a molecular test can confirm it. The two tests often work together rather than replacing each other.

Your oncologist will explain which combination was ordered for your cancer and what the results mean for your care. Interpreting a full marker panel is a specialist conversation — drawing conclusions from the report alone, before that conversation, rarely helps.

Did you know?

Two tumours of the same type — same organ, same stage — can have completely different marker profiles. This is why two people with an identical diagnosis sometimes receive different treatments: the biology of the tumour, not the label on the diagnosis, increasingly decides the approach.

According to ESMO and NCCN clinical practice guidelines, biomarker profiling now informs treatment decisions across more than a dozen major cancer types, including cancers of the breast, lung, colon, stomach and cervix.

Source: ESMO and NCCN Clinical Practice Guidelines on Biomarker Testing

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Common questions

Frequently asked questions

What does positive or negative mean for a marker?

Positive means the laboratory detected that protein on the cancer cells in a meaningful amount; negative means it was not detected, or was detected at too low a level to be considered significant. Neither result is automatically good or bad news — what it means depends entirely on which marker it is and your cancer type. Your oncologist will explain the significance of each result in your specific situation, because the same positive result can have very different implications for different cancers.

Why does my biopsy report show so many numbers and percentages?

Each number refers to a different measurement. A percentage next to ER or PR shows what proportion of cancer cells stained positive for that receptor. A score like 1+ or 3+ next to HER2 indicates how strongly the protein was expressed. Ki-67 is often reported as a percentage of cells that were actively dividing at the time of the biopsy. These numbers are the pathologist's observations. Your oncologist translates them into clinical meaning — reading them without that context rarely helps and can cause unnecessary anxiety.

Does a positive HER2 result mean the cancer is more aggressive?

HER2-positive means the cancer cells carry more of a particular growth-signalling protein than normal cells do. It does not automatically mean the cancer is more advanced or more dangerous. What it does is give your oncologist more specific information about what is driving the tumour, which informs the most appropriate treatment approach. The significance of any individual result depends on the full picture — the cancer type, the stage, and every other test done alongside it. Ask your oncologist to explain what your full panel means together.

Can the markers change if the cancer returns or spreads?

Yes. A tumour that recurs or spreads to a new site can develop different marker results compared to the original biopsy. This is why oncologists sometimes recommend a repeat biopsy if the cancer comes back — to check whether the profile has changed, because a different profile may point to a different approach. It does not mean the first biopsy was wrong. Tumours can change over time, and the new result describes where the disease is now rather than where it started.

How long does IHC and molecular testing take?

Basic IHC testing typically takes a few days to a week. Molecular testing, which sequences the tumour's DNA, usually takes one to two weeks, and some specialised panels can take longer if the sample has to be sent to a reference laboratory. Ask your team when the sample was dispatched and when results are expected, so you have a clear timeline. Waiting is genuinely hard — knowing the timeline helps. Your team will usually have a plan ready to discuss once all results are back.

What should I ask my oncologist when going through the marker results?

Ask which markers were tested and why those specific ones apply to your cancer type. Ask what each positive or negative result means for your situation — not in general, but for you specifically. Ask whether any molecular testing is still pending. Ask whether the results open up any particular treatment pathways, and whether a second opinion on the pathology would be useful. You do not need to interpret the report before the appointment — bring it with you and go through it together.

Full index

Browse all 701 biopsy topics

Every page in this section, grouped by the part of the journey it belongs to. Pick a group to see what is in it.

What Is a Biopsy?

What Is a Biopsy? Everything You Need to Know →

Types of Biopsy Compared

Which Biopsy Will You Have? Techniques Compared →

Preparing for a Biopsy

What to Expect on the Day of Your Biopsy →

Recovery and Aftercare

After a Biopsy: Recovery, Aftercare and Warning Signs →

Biopsy by Body Part

Biopsy by Body Part: What to Expect at Each Site →

Understanding Your Report

How to Read a Biopsy Report: Terms Explained →

IHC and Molecular Markers

Grading and Scoring Systems

Cytology & Prostate Scoring Systems Explained →

How Accurate Is a Biopsy?

How Accurate Is a Biopsy? Errors and Second Opinions →

If Your Result Is Benign

Your Biopsy Is Benign: What It Means and What Comes Next →

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