At a glance

Also known as


Why get tested?

To determine whether a breast cancer tumour is positive for HER2/neu, which helps to guide treatment decisions and determine outcome

When to get tested?

If you have been diagnosed with invasive breast cancer and your doctor wants to determine whether the HER2/neu gene is being over-expressed in the tumour

Sample required?

A sample of breast cancer tissue obtained during a biopsy; sometimes a blood sample, drawn from a vein in your arm, is also required

Confused about genetics?

See our Genetics Information page

What is being tested?

HER2/neu is an oncogene. It codes for a receptor for a particular growth factor that causes cells to grow. Normal epithelial cells contain two copies of the HER2/neu gene and produce low levels of the HER2 protein on the surface of their cells. In about 20-30% of invasive breast cancers (and some other cancers, such as ovarian and bladder cancer), the HER2/neu gene is amplified (far too many copies are produced) and its protein is over-expressed (an abnormally large amount of the protein is produced). Cancers that have this over-expression tend to grow more aggressively and resist hormonal therapy and some chemotherapies, and patients generally have a poorer outcome.

There are two main ways to test HER2/neu status in cancer tissue: immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH). IHC measures the amount of HER2/neu protein present. FISH looks at the genetic level for actual gene amplification – the number of copies of the HER2 gene present.

How is the sample collected for testing?

A sample of breast cancer tissue is obtained by doing a fine needle aspiration, needle biopsy or surgical biopsy. HER2/neu protein is sometimes measured in a blood sample drawn from a vein in the arm. The amount of HER2/neu protein present in serum is loosely associated with the amount of cancer present; however it will not be positive until the tumour is fairly big and is not widely used for determining HER2/neu status.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

How is it used?

HER2/neu testing is primarily used to select patients for treatment with Herceptin (trastuzumab). It may also be used to help determine how aggressive a breast cancer tumour is likely to be.

It is also used as a predictor of response to certain types of chemotherapy and hormone therapy but these findings require further validation.

The serum HER2/neu test is sometimes used to monitor cancer therapy. If the level is initially elevated then falls, it is likely that treatment is working; if it stays elevated, treatment is not working; and if the level falls then rises, the cancer may be recurring.

When is it requested?

HER2/neu testing is recommended as part of an initial work-up of invasive breast cancer and is sometimes done with recurrent breast cancer. It is not diagnostic but helps the doctor determine treatment options and understand more about the tumour’s characteristics.

Serum HER2/neu is sometimes requested initially to establish a baseline and then, if elevated, used to monitor cancer treatment.

What does the test result mean?

A positive (IHC) HER2/neu test means that the HER2/neu gene is over-expressing (producing an excess amount of) HER2/neu protein. If a FISH test is done, then amplification production of too many copies) of the HER2/neu gene can be detected. If either test is positive, the patient is likely to have an aggressive tumour. HER2 positive patients are potential candidates for Herceptin therapy. [See "Is there anything else I should know?"].

Currently, Herceptin is approved in Australia for the treatment of HER2/neu positive early stage breast cancer and HER2/neu positive advanced breast cancer.

If the IHC test is negative but the FISH test is positive, the patient may still benefit from Herceptin, but if both are negative the treatment will not be useful.

About Reference Intervals

Is there anything else I should know?

HER2/neu-positive tumours may be susceptible to Herceptin (trastuzumab), a therapy created to target HER2/neu protein. Herceptin, an antibody made in the laboratory, attaches itself to the excess protein molecules and inhibits the growth of the cancer. The development of this specialised therapy has increased the use of HER2/neu testing. Herceptin may be used alone or with some chemotherapy agents but is only useful in those who have HER2/neu amplification and protein over-expression.

Tissue HER2/neu testing is not available in every laboratory. Both IHC and FISH require experience and special training to perform and to interpret.

Herceptin use has also been approved in Australia for use in advanced cancers of the stomach, if they are shown to be HER2 positive.

Common Questions

Besides HER2/neu, what other laboratory tests may my doctor request on my breast cancer tissue?

During an initial workup of invasive breast cancer, your doctor is likely to do a tissue test for hormone receptor status. A patient with a positive oestrogen and/or progesterone receptor status may find their response to endocrine or hormone therapy diminished if they are also HER2/neu-positive, limiting that treatment option.

Does Herceptin work for everyone who is HER2/neu positive?

Unfortunately, no. Only about one-third of patients who are positive for HER2/neu will respond to Herceptin therapy. There are other cellular factors involved that are not yet well understood. Herceptin is sometimes combined with other chemotherapy agents to make it more effective.

Are there any other cancers in which HER2 testing is useful?

Cancers of the stomach and lower oesophagus may be HER2 positive. The use of Herceptin is also approved in Australia in cases of HER2 positive advanced cancer of the stomach, where anti-cancer medications have not yet been commenced.

Last Review Date: February 4, 2018

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