icon Immunohistochemistry

What is Immunohistochemistry (IHC)?

Immunohistochemistry (IHC) is a diagnostic technique conducted in a laboratory. It involves performing special tests on the patient's biopsy tissue sample to help diagnose disease more precisely. IHC helps the care team distinguish between different types and subtypes of a disease by identifying specific molecules within cells, known as markers.

Why this test is done?

Immunohistochemistry is particularly useful in diagnosing certain types of cancer, providing the care team with a wealth of information about the disease to help determine treatment, such as:

  • Where the cancer started
  • The type of cell it started in
  • Whether it’s likely to grow slowly or quickly

Immunohistochemistry may help provide these answers.

How to collect the specimen?

To perform an IHC test, the care team must collect a tissue sample. The procedure to remove an abnormal or cancerous specimen is called a biopsy. Methods range from needle biopsies, which involve inserting a needle into the tumor, to excisional biopsies, which remove the entire tumor. The method used depends on individual circumstances, including the type of cancer and its location.

All biopsy types involve removing bodily tissue and taking it to a laboratory, where a pathologist who specializes in diagnosing diseases will examine the sample under a microscope. To determine whether or not the specimen is cancerous, the pathologist usually only needs to examine the cells and perform standard tests called stains, which use colored substances (dyes) to highlight cancer cells.

It may be difficult to differentiate cancer cells from healthy ones based only on their appearance and routine tests. When these methods aren’t enough to make a diagnosis, the care team may turn to IHC.

How does immunohistochemistry work?

Immunohistochemistry reveals more than a standard biopsy test. It enables pathologists to determine the exact type and subtype of cancer by looking for unique tumor markers within cancer cells. Markers are identified using antibodies, a type of protein that locates and binds with antigens (which are the markers found on cells). Antigens are like cellular locks and antibodies are like keys—unique antibodies fit perfectly within their respective antigens.

More than 400 unique antibodies can be used in IHC tests. When an antibody recognizes and binds to corresponding antigen in the sample, a colored dye is activated, indicating to the pathologist that the sample contains a particular type of cell that may help determine the exact type of cancer.

Reasons for Referral?

The doctor and a pathologist typically determine whether or not immunohistochemistry is necessary on a case-by-case basis.

However, IHC tests are routinely used to help diagnose most types of breast cancer, including:

In patients with breast cancer, immunohistochemistry is used to test for the conditions listed below.

Hormone receptor status: IHC tests may detect the presence or absence of hormone receptors on breast cancer cells. This knowledge informs how the cancer may be treated, as breast cancers that carry these receptors can be treated with hormone therapy drugs.

HER2 status: IHC tests may check for HER2 receptors to determine whether breast cancer is HER2-positive or HER2-negative. If these receptors are found, the cancer is HER2-positive, which indicates that it’s likely to be fast-growing and may be treated by targeted therapy drugs that block the effects of the HER2 proteins responsible for fueling the cancer’s growth.

Another routine use of IHC testing is for Lynch syndrome, an inherited condition that may cause cancer or increase one’s risk of developing cancer. Lynch syndrome is most often linked to colorectal cancer, but it may also raise the risk for developing cancer in the uterus, stomach, liver, kidney and brain. Doctors may recommend using IHC to check for markers of Lynch syndrome in women who develop endometrial cancer, or anyone diagnosed with colorectal cancer before age 70.

For other cancer types, IHC testing may be warranted under certain circumstances. These include the following cancer types.

Gastrointestinal cancer: Some gastric cancers are linked to autoimmune diseases or bacterial strains, such as H. pylori. IHC tests may help inform treatment by determining whether these or other factors may be responsible for causing the cancer. IHC tests can also help differentiate between types of gastrointestinal cancer.

Prostate cancer: Some prostate cancers are difficult to diagnose using standard tests. Numerous antibodies may be used in IHC tests to learn more about the cancer, although performing these tests isn’t always necessary. IHC tests are more likely to be used if standard tests reveal mixed findings.

Lung cancer: After other tests confirm a lung cancer diagnosis, IHC tests may be necessary to define the type of lung cancer. For example, a pathologist will often need to use IHC to check for specific antigens to establish a case of non-small cell lung cancer.

Lymphoma: It may be difficult for a pathologist to recognize whether swollen lymph nodes are caused by an infection or cancer such as lymphoma. With IHC tests, the pathologist is able to test the white blood cells causing the swelling to see whether they carry cancer-indicating antigens. IHC tests may also help distinguish between different lymphoma types.

Other cancers that may sometimes need IHC testing include those of the female reproductive system, bladder and kidney. However, many other circumstances warrant using the IHC method. The decision to use IHC tests is based on careful consideration of individual factors.

Test Preparation:
No test preparation is needed.

Sample Requirement:

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