Reading your pathology report

How Many IHC Markers — Do You Actually Need?

Your pathology report may list two markers or twelve. Neither number is automatically right. The correct panel size is the smallest one that answers the diagnostic question — and knowing that can save you real money.

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

Bigger is not more accurate — More markers do not sharpen the answer once the diagnostic question is answered. They add cost and can create results that are harder to interpret.
The pathologist decides — Panel size is a clinical judgement, not a convention. The pathologist chooses based on what the cells look like under the microscope.
Over-testing is real — Panels are sometimes ordered beyond what the question requires. This costs more and uses tissue that may be needed for repeat testing later.
One marker, one question — Each marker in a well-designed panel answers one part of the diagnostic question. If you cannot say what a marker was for, that is worth asking.

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The number of IHC markers in a panel depends on the diagnostic question, not a fixed standard. A focused panel of a few markers often gives a complete answer. More markers are added only when the cell origin is genuinely unclear. Bigger is not more accurate — restraint is a sign of expertise.

What do the terms on an IHC report mean?

IHC (immunohistochemistry): A laboratory technique that uses antibodies to detect specific proteins inside tumour cells. The result tells the pathologist what type of cell the tumour came from.
Marker: A specific protein the laboratory tests for. Each marker is chosen because its presence or absence answers part of the diagnostic question.
Panel: The set of markers ordered together on one tissue sample. Size is not fixed — it depends on how complex the diagnostic question is, not on any rule.
Positive (+) / Negative (−): Whether the target protein was detected in the tumour cells. Neither result is automatically good or bad. The meaning depends entirely on which marker is being reported and the clinical context.
Expression: How strongly, and in what proportion of cells, a marker was detected. Often reported as a score — such as 1+, 2+, or 3+ — rather than a simple yes or no.
Equivocal: The result fell between clearly positive and clearly negative and cannot be used with confidence in either direction. The pathologist may recommend further testing to resolve it.

How can you tell if your IHC panel was the right size?

The pathologist's conclusion follows directly from the markers tested.
Your oncologist can explain what clinical question each marker was chosen to answer.
Every marker on the report has a result — none listed as not done without explanation.
The panel does not include markers whose results were already made irrelevant by earlier ones.
If the panel is large, your oncologist can explain why fewer markers were not enough to answer the question.

Focused panel versus extended panel — what actually changes?

	Focused panel	Extended panel
When used	Morphology strongly suggests the diagnosis	Origin is unclear; several diagnoses are possible
Cost	Lower	Higher — each marker is typically billed separately
Turnaround time	Usually faster	Can take longer depending on the laboratory
Does more mean more accurate?	Not if the question is already answered	Only if each extra marker resolves a specific remaining uncertainty
Who decides the size	Pathologist, based on what the cells look like	Pathologist, with the clinical picture from your oncologist

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Who decides how many markers you need?

The pathologist decides — based on what the cells look like under the microscope and the clinical question your oncologist has asked. A well-trained pathologist orders the smallest number of markers needed to reach a clear answer, then stops.

Adding markers beyond what the question requires does not improve accuracy. It adds cost, can add days to the turnaround, and sometimes produces results that are harder to interpret than a smaller, focused panel.

If your report has many markers and you are unsure whether all were necessary, ask your oncologist to explain the reasoning. That is a legitimate question to raise at your next appointment.

Did you know?

The College of American Pathologists advises pathologists to select the smallest panel of markers that will reliably answer the diagnostic question — not the largest panel possible.

Restraint in panel design is a mark of expertise, not a cost-cutting compromise.

Source: College of American Pathologists (CAP) — Practice Guidelines for Immunohistochemistry

What do families ask most about IHC panel size?

Is a bigger IHC panel always better?

No. A panel of two or three markers can give a definitive answer for many cancers. Adding markers beyond what the question requires does not improve accuracy — it adds cost, uses tissue that is a finite resource, and occasionally produces results that need their own interpretation. Expertise in panel design shows in choosing the right markers, not the most markers.

Can you genuinely be over-tested on IHC?

Yes. Over-testing happens when markers are ordered out of habit or to cover all possibilities rather than to answer a specific question. Each marker uses a portion of the tissue block. A block used for a very large panel may have less material available if repeat testing is needed later — for a second opinion, or if the disease changes. Appropriate panel design protects both your wallet and your tissue.

Why does one report have two markers and another have twelve?

The number reflects the complexity of the diagnostic question, not the severity of the cancer. A tumour with very characteristic features under the microscope may need only two markers to confirm the diagnosis. A tumour of uncertain origin — where cells could plausibly have come from several different sites — requires more markers to work through the possibilities systematically. A large panel means the diagnosis was genuinely difficult to establish, not that more is wrong with you.

What if I want more markers tested?

Raise it with your oncologist, who will tell you whether additional testing would change the diagnosis or the plan. If the question is already answered, more markers will add cost without adding information and will use tissue that may be needed later. If genuine uncertainty remains in the current report, your oncologist may agree that further testing is warranted. The right question to ask is: 'Is there something the current panel leaves unanswered?' rather than 'Can we add more?'

What does an equivocal marker result mean for me?

Equivocal means the result fell between clearly positive and clearly negative. This is not a laboratory failure — some tumours genuinely express proteins at borderline levels. Your pathologist may recommend repeat testing on fresh tissue, a different antibody clone for the same marker, or an additional marker that approaches the question from a different angle. Your oncologist will explain what the equivocal result means for your specific situation and whether further testing is planned.

Should I get a second IHC panel done privately?

A repeat panel on the same tissue block rarely changes the result, because the same sample is tested with the same validated methods. What genuinely helps in uncertain cases is a second pathology opinion — a second pathologist reviewing the same slides and results. If you are uncertain about your report, ask your oncologist about a second pathology opinion rather than a repeat panel. That is what adds new information, not repeating the same test.

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Common questions

Frequently asked questions

What is an IHC panel exactly?

An IHC panel is the set of markers tested together on a single tissue sample. The pathologist chooses which markers to include based on what the cells look like and what diagnostic question needs answering. A panel of two and a panel of ten are both panels — the number reflects the complexity of the diagnostic question, not a fixed standard. Each marker adds one piece of evidence, and the pattern of results taken together is what allows the pathologist to reach a conclusion.

How do I know if my panel was the right size?

The clearest sign is that the pathologist's conclusion follows directly from the markers tested. If the report lists markers whose results are not mentioned in the conclusion, it is worth asking your oncologist what they contributed. You can also ask whether the diagnosis would have been the same with fewer markers. A pathologist confident in their conclusion can usually explain why each marker was chosen and what it ruled in or out.

Can I ask for extra markers to be added after the report is done?

You can raise it with your oncologist, who will tell you whether additional testing would change the diagnosis or the plan. If the diagnostic question is already answered, more markers will not improve your situation and will use remaining tissue. If genuine uncertainty remains, your oncologist may agree that further testing is worth doing. Start with: 'Is there something the current panel does not answer?' rather than asking for more markers by name.

Does a larger IHC panel cost significantly more?

Each marker is typically billed separately, so a larger panel costs more than a focused one. The exact amounts vary by laboratory and institution, and any figure you are quoted should be treated as indicative. If cost is a concern, it is reasonable to ask how many markers are planned before testing is done. In most cases a pathologist will not order more than the question requires — but asking beforehand is fair and practical.

What happens if a marker result is equivocal?

Equivocal means the result fell between clearly positive and clearly negative and cannot be used with confidence in either direction. Your pathologist may recommend retesting on fresh tissue, a different antibody clone, or an additional marker that resolves the uncertainty from another angle. This is not a failure of the test — some tumours genuinely sit at borderline levels. Your oncologist will explain what the equivocal result means and whether further testing is planned.

My report shows some markers positive and others negative. What does that mean overall?

The combination — which markers are positive and which are negative — is itself the diagnostic pattern. Certain tumour types have characteristic combinations, and the panel is designed to reveal exactly that pattern. Do not read individual results as good news or bad news in isolation. The meaning comes from the whole picture, which your pathologist and oncologist interpret together based on your specific report and clinical situation.

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