Immunohistochemistry: What Is It and How Does It Work?

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What Is Immunohistochemistry Staining?

Immunohistochemistry uses antibodies to test tissue samples for specific types of antigens. It can often provide very specific results regarding cancer types or other diseases, helping doctors decide on treatment options.

Immunohistochemistry (IHC) is a widely used staining technique that allows doctors to detect certain cancers and infectious diseases more easily.

Since its introduction in 1941 , scientists have adapted and improved the technique multiple times. It’s now a standard part of diagnostic testing for some cancers, as it can provide very specific information.

Keep reading to learn how IHC works and why it’s often an essential tool for doctors.

Doctors use IHC to identify the presence of certain antigens on cells. An antigen can be a toxin, virus, bacterium, or other particle that doesn’t belong in your body.

Many types of cancer cells also have antigens on their surface. Scientists call these tumor-specific antigens. Detecting a tumor-specific antigen could help a doctor determine what type of cancer is present. It could also inform doctors about other important genetic traits, such as the presence of tumor cell DNA mutations.

IHC uses antibodies to detect antigens. An antibody is a molecule that tightly binds to an antigen. Your immune system makes antibodies, but scientists make the antibodies for IHC staining in a laboratory.

Antibodies chemically bind to antigens to help your immune system counter their effects. Specific antibodies bind to specific antigens.

In IHC, pathologists (doctors who examine cells for signs of disease) equip a specific antibody with a dye. When the antibody binds with its antigen, the dye activates. This process is called staining.

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The pathologist takes a sample of tissue obtained from a biopsy. They will test the tissue sample with the antibodies and look for the activation of the dye under a microscope. Because antibodies bind to a specific antigen, IHC staining allows pathologists to determine exactly which antigen is present, helping to make an accurate diagnosis.

Pathologists can often find cancer cells under a microscope without using IHC. But it can sometimes be challenging to identify the specific type of cancer. They may also just need to know more about the cancer.

Before a doctor recommends expensive targeted therapies to treat a specific cancer, they must first perform IHC to confirm the presence of specific tumor cell mutations that will make their patient eligible for the treatment. This process is called companion diagnostics .

Doctors don’t always request IHC, but it may help in some of the following cancers:

Breast cancer

IHC can let doctors know whether or not breast cancer cells have HER2, progesterone, or estrogen receptors on them. This can influence treatment and affects your outlook.

Lymphomas

There are more than 90 different subtypes of lymphoma. IHC is an essential test to help determine the subtype, as well as detect specific gene alterations and help see how much the cancer has spread.

Stomach cancer

IHC is the most accurate staining method to help detect the presence of Helicobacter pylori (H. pylori) bacteria, the leading cause of stomach cancer worldwide.

Prostate cancer

If standard prostate cancer tests don’t reveal enough information, a doctor may order IHC testing. According to 2018 research, IHC can provide more specific information about prostate cancer cells and insight into outlook and treatment options.

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Lung cancer

IHC can help distinguish between small-cell and non-small-cell lung cancer. According to 2019 research, IHC is also necessary to help diagnose certain uncommon types of lung cancer.

IHC can also check for specific cancer cell mutations which, when present, allow for the use of life-saving immunotherapy. Other cancers follow similar protocols.

Lynch syndrome

IHC testing can help determine whether you have Lynch syndrome, a condition that increases your risk for several cancers, including :

  • colorectal
  • endometrial (uterine)
  • ovarian
  • gastrointestinal
  • urinary tract
  • pancreas and biliary tract

Benefits of immunohistochemistry

Some of the qualities that have helped IHC become so widely used include :

  • specific test results
  • cost-effectiveness
  • quick turnaround
  • can use fresh, frozen, or paraffin-embedded tissue samples

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