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Also known as: ERBB2; c-erbB-2; HER2 Serum
Formal name: HER2/neu Amplification by FISH; HER2 Overexpression by IHC; HER2 Quantitative, Serum

At a Glance

Why Get Tested?

To determine whether a breast cancer tumor is positive for HER2/neu, which helps to guide treatment and predict the course of the disease (prognosis); sometimes to monitor treatment and for cancer recurrence

When to Get Tested?

When you have been diagnosed with invasive breast cancer

Sample Required?

A sample of breast cancer tissue obtained during a biopsy or a tumor removed surgically during a lumpectomy or mastectomy; sometimes a blood sample drawn from a vein in your arm

Test Preparation Needed?


The Test Sample

What is being tested?

HER2/neu is short for the human epidermal growth factor receptor 2. It is a gene that is found in healthy cells, but some people with breast cancer have tumors with excess copies of the gene and amounts of the protein it produces. Breast tumors in this category are known as HER2/neu-positive and can be more aggressive and respond differently to treatment than HER2/neu-negative tumors. The HER2/neu test performed on breast tissue determines whether a person's breast cancer is positive for HER2/neu.

In normal cells, the HER2/neu gene codes for a protein that helps promote cell growth. But when a gene mutation results in too many copies in a cell (amplification), HER2/neu then produces too much of the HER2 protein. When this happens, HER2/neu becomes an oncogene, meaning that it can promote uncontrolled, cancerous growth. This only happens in about one in five breast cancers but can also happen in other cancers, such as ovarian and bladder cancer.

Tumors that have this overexpression tend to grow more aggressively and resist endocrine (anti-hormone) therapy and some standard chemotherapies. People with HER2/neu-positive breast cancers tend to have a poorer prognosis, but this tumor characteristic also makes them candidates to receive treatment specific for HER2/neu-positive cancers, also known as targeted therapy.

The American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP) jointly recommend that the tumors of all people with invasive or recurrent breast cancer be tested for HER2/neu.

To determine if a tumor is positive for HER2/neu, a biopsy is taken and the sample of tumor is tested. There are two main ways to test HER2/neu status:

  • Immunohistochemistry (IHC) measures the amount of HER2 protein present.
  • Fluorescent in situ hybridization (FISH) looks at the genetic level for the number of copies of the gene present, known as amplification.

Both IHC and FISH are acceptable testing methods, according to ASCO and CAP. The panel does not express a preference for one over the other. But if one test is indeterminate or negative, then the other should be done as a follow-up test.

Blood testing
Cells shed HER2 protein into the blood and a serum test is available to measure the amount of HER2 protein present in the blood of a person diagnosed with breast cancer. The serum level is loosely associated with the amount of HER2/neu-positive cancer present.

This test is not used for screening purposes and is not a substitute for tissue testing but may be ordered to help assess a person's prognosis and to monitor the effectiveness of treatment.

After an initial diagnosis of metastatic breast cancer is made, this blood test may be performed and if the initial level (baseline) is greater than 15 ng/mL, then the test may be used to monitor treatment. HER2 blood levels that remain high or drop and then increase could indicate that treatment is not working.

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. For the HER2 blood test, a blood sample is drawn from a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

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

No test preparation is needed.

The Test

Common Questions

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

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Ithimakin, Suthinee et al. HER2 Drives Luminal Breast Cancer Stem Cells in the Absence of HER2 Amplification: Implications for Efficacy of Adjuvant Trastuzumab. Cancer Research. February 2013. Available online at http://cancerres.aacrjournals.org/content/early/2013/02/14/0008-5472.CAN-12-3349.abstract through http://cancerres.aacrjournals.org. doi: 10.1158/0008-5472.CAN-12-3349 Accessed July 2013.

(Copyright 2012). Breast Cancer and Breast Pathology. John Hopkins University. Available online at http://pathology.jhu.edu/breast/biomarker-testing.php through http://pathology.jhu.edu. Accessed July 2013.

(Updated December 2012) HER2/neu Testing. Quest Diagnostics. Available online at http://www.questdiagnostics.com/testcenter/testguide.action?dc=CF_HER_2 through http://www.questdiagnostics.com. Accessed July 2013.

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(©2012). What to Know: ASCO's Guideline on HER2 Testing for Breast Cancer. American Society of Clinical Oncologists. Available online at http://www.cancer.net/publications-and-resources/what-know-ascos-guidelines/what-know-ascos-guideline-her2-testing-breast-cancer through http://www.cancer.net. Accessed July 2013.

(Updated June 2011). Serum HER2 Testing. Atlantic Health System. Available online at https://atlantichealth.dnadirect.com/grc/patient-site/her2-serum/index.html through https://atlantichealth.dnadirect.com. Accessed July 2013.

(November 2008) ARUP Laboratories Technical Bulleting. HER-2/neu Serum For monitoring soluble HER-2/neu protein in patients with metastatic breast cancer. Available online at http://www.aruplab.com/Testing-Information/resources/TechnicalBulletins/HER-2neu%20Serum.pdf through http://www.aruplab.com. Accessed August 2013.

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Lam L, et al. Challenges in the clinical utility of the serum test for HER2 ECD. Biochim Biophys Acta. 2012 August; 1826(1): 199–208. Available online at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3362659/ through http://www.ncbi.nlm.nih.gov. Accessed October 2013.

Gregory J. Tsongalis, PhD, HCLD, CC, Professor of Pathology, Director, Molecular Pathology, Dartmouth Hitchcock Medical Center and Geisel School of Medicine at Dartmouth, Lebanon, NH.

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