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Biopsy & pathology

Immunohistochemistry explained

The antibody stains that identify exactly what your biopsy cells are - and increasingly, which treatments will work on them.

Key facts

At a glance

  • The method: antibodies tagged with dye bind to specific proteins on your tissue slides, lighting up the cells that carry them.

  • Job one - identity: marker panels establish what a tumour is and where it came from, including in cancers of unknown primary.

  • Job two - treatment prediction: ER, PR and HER2 in breast cancer, PD-L1 for immunotherapy, mismatch repair proteins - stains that directly select drugs.

  • The time cost: each staining round adds a day or two to your report - a wait that buys precision.

  • Follow-up: marker results appear as codes on your report; your specialist translates them into the treatment options they unlock.

The full picture

What this test involves, and how to get it

Immunohistochemistry (IHC) is how pathology moved beyond appearances. Antibodies engineered to bind one specific protein are washed over your tissue slides, carrying a colour tag - wherever the protein exists, the cells stain, turning identity into something visible. Deployed as panels, these stains settle questions morphology cannot: whether a poorly differentiated tumour is carcinoma, lymphoma or melanoma (their treatments differ entirely); which organ a metastasis originally came from in cancer of unknown primary; whether a lymphoid population is reactive or lymphoma, and which subtype. The cryptic codes on reports - CK7, TTF-1, CD20, S100 and dozens more - are this process’s vocabulary, each marker a protein with a known distribution across cell types.

IHC’s second job now rivals the first: predicting treatment response. Breast cancer’s ER, PR and HER2 status - determining hormone therapy and HER2-targeted drugs - is IHC; PD-L1 scoring guides immunotherapy in lung and other cancers; mismatch repair protein staining screens bowel and womb cancers for Lynch syndrome and immunotherapy sensitivity; Ki-67 indexes how fast cells are dividing. Each staining round adds a day or two to the report - the standard explanation for a biopsy result arriving in instalments, with "further results to follow" on the first letter. The stains run in accredited NHS and private laboratories alike, ordered by the pathologist as the case demands rather than by request; what patients can usefully do is ask their specialist to walk through which markers were tested and what each one opened or closed - because in modern oncology, the IHC line on your report is frequently the sentence that chose your treatment.

A quiet reminder

This guide is for information, not medical advice.

Your own clinician knows your history and can tell you which parts apply to you. Next review of this page: 2027-09-27.

Frequently asked

Common questions about Immunohistochemistry explained.

Quick, plain-English answers to what people ask us most.

  • What is immunohistochemistry?

    Immunohistochemistry (IHC) is a specialised laboratory technique used on tissue samples, most often biopsy or surgical specimens, that uses labelled antibodies to detect specific proteins within cells. It helps pathologists identify the exact type and characteristics of abnormal cells, particularly in cancer diagnosis.

  • Why would immunohistochemistry be used on my sample?

    It is commonly used to help confirm the type and origin of a tumour, distinguish between similar-looking conditions under the microscope, and identify specific markers that can guide treatment decisions, such as certain receptor statuses in breast cancer.

  • Do I need to prepare for immunohistochemistry testing?

    No preparation is needed from you directly, since IHC is performed on a tissue sample that has already been collected, usually via a biopsy or surgical procedure you have already had.

  • What happens during immunohistochemistry testing?

    In the laboratory, thin sections of your tissue sample are treated with specific antibodies that bind to particular proteins, which are then made visible under the microscope using a staining technique, allowing the pathologist to see which cells express which markers.

  • How long do immunohistochemistry results take?

    Because it is performed in addition to standard histology, IHC can add several days to two weeks to your overall pathology reporting time, depending on how many markers are tested and laboratory workload.

  • What do the results mean, and what happens next?

    IHC results help refine or confirm a diagnosis and, in cancer specifically, can influence treatment choices by identifying markers linked to particular therapies. Your doctor or specialist will explain what your specific results mean for your diagnosis and treatment plan, as interpretation is highly individual.

  • Is immunohistochemistry accurate and reliable?

    IHC is a well-established and widely used technique that adds valuable diagnostic precision to standard histology, though like any laboratory test, results are interpreted by an experienced pathologist alongside the overall clinical and microscopic picture.

  • How much does private pathology review including immunohistochemistry cost?

    Private specialist pathology services can arrange additional testing, including immunohistochemistry, or a second opinion on existing results, with cost varying by provider depending on the complexity of testing required.

  • Is immunohistochemistry available on the NHS?

    Yes, it is a standard part of NHS pathology services when clinically indicated, most commonly in cancer diagnosis pathways.

  • How do I get a private second opinion involving immunohistochemistry?

    Private pathology specialists can review existing tissue samples and results, sometimes requesting further immunohistochemistry stains, usually within a matter of days to a week or two, which can be helpful if you want additional reassurance or clarity.