What is a HER2 Tumor Marker Test?
A HER2 Tumor Marker Test checks cancer cells for increased amounts of HER2 (human epidermal growth factor receptor 2) protein or extra copies of the HER2 gene. HER2 is a protein that helps cells grow and divide. Some cancers have abnormally high levels of HER2, which can cause cancer cells to grow more quickly.
HER2 testing is most commonly performed for breast cancer and may also be used for certain stomach and gastroesophageal junction cancers. The results help healthcare providers determine whether a cancer is HER2-positive and whether the patient may benefit from HER2-targeted treatments. Common HER2 testing methods include:
Immunohistochemistry (IHC): Measures the amount of HER2 protein on cancer cells.
Fluorescence In Situ Hybridization (FISH): Determines whether cancer cells contain extra copies of the HER2 gene.
Other in situ hybridization tests: May also be used to assess HER2 gene amplification.
HER2 testing is generally performed on tumor tissue collected during a biopsy or surgery.
How is the Test Performed?
Preparation
- Fasting is usually not required unless you are getting medicines to relax or sleep during the
- procedure; then you might have to fast for several hours.
- Inform your healthcare provider about your cancer diagnosis and previous treatments.
- Follow any instructions provided before a biopsy or surgical procedure.
- Discuss the purpose and possible implications of HER2 testing with your healthcare provider.
Collection
- A tissue sample may be obtained through a biopsy or during surgery.
- The collected tissue is preserved and sent to a pathology laboratory.
- In some cases, previously collected tumor tissue may be used, so a new biopsy may not be necessary.
- The procedure and preparation requirements depend on how the tissue sample is obtained.
Lab Analysis
The tumor tissue is analyzed using specialized techniques such as Immunohistochemistry (IHC) to measure HER2 protein levels or Fluorescence In Situ Hybridization (FISH) to determine whether the HER2 gene is amplified. The results help classify the tumor’s HER2 status and guide decisions about targeted cancer treatment.
What are the Symptoms that Prompt this Test?
A HER2 Tumor Marker Test is generally performed after a cancer diagnosis to determine whether tumor cells produce too much HER2 protein or have extra copies of the HER2 gene. It is not typically ordered based on symptoms alone.
Situations and Conditions That May Prompt This Test
Your healthcare provider may recommend a HER2 Tumor Marker Test if you have:
- Newly diagnosed breast cancer
- Recurrent breast cancer
- Advanced or metastatic breast cancer
- Newly diagnosed stomach cancer
- Gastroesophageal junction (GEJ) cancer
- Cancer that has returned after treatment
- A tumor that may be eligible for HER2-targeted therapy
HER2 testing is especially important in breast cancer because HER2-positive tumors may grow more quickly but may also respond to specific HER2-targeted treatments.
What are Normal Ranges for This Test?
The HER2 tumor marker normal range depends on the testing method used.
Immunohistochemistry (IHC)
HER2 protein expression is commonly graded as:
- 0 (Zero): HER2- Negative
- 1+: HER2- Negative
- 2+: Borderline/ equivocal; additional testing may be required, such as FISH or another validated gene amplification test.
- 3+: HER2- Positive
Fluorescence In Situ Hybridization (FISH)
FISH testing evaluates whether there are extra copies of the HER2 gene. Results may be reported as:
HER2 amplified: Extra copies of the HER2 gene are detected.
HER2 not amplified: No significant HER2 gene amplification is detected.
“The reference ranges vary depending on the laboratory and the methodology used. Individuals must consult their healthcare provider for correct interpretation of the results.”
What Happens if Test Results Show Abnormal Findings?
Abnormal HER2 Tumor Marker Test results indicate that cancer cells may have increased HER2 protein expression or HER2 gene amplification.
HER2-Positive Result
A HER2-positive result may indicate:
- Increased HER2 protein expression
- HER2 gene amplification
- A greater likelihood that the cancer may respond to HER2-targeted treatment
Depending on the cancer type and stage, your healthcare provider may consider HER2-targeted therapies as part of the treatment plan.
HER2-Negative Result
A HER2-negative result generally means that the tumor does not have enough HER2 protein or gene amplification to be classified as HER2-positive.
However, HER2-negative cancers may still have other biomarkers that can influence treatment decisions.
Equivocal or Borderline Result
An equivocal result, commonly associated with an IHC score of 2+, means the HER2 status cannot be determined by IHC alone.
Your healthcare provider may recommend:
- FISH testing
- Other in situ hybridization testing
- Repeat HER2 testing on another tumor sample
Depending on the results, your healthcare provider may recommend additional investigations such as BRAF Genetic Testing, Lung Cancer Genetic Tests, Tumor Marker Tests, or comprehensive molecular profiling.
Need a HER2 Tumor Marker Test? Book your appointment today for reliable cancer biomarker testing and expert pathology laboratory support.
