HER2 (Human Epidermal growth factor Receptor 2) is a protein that can promote the growth of cancer cells. In certain cancers, particularly breast cancer, the HER2 gene can be amplified, leading to an overexpression of the HER2 protein. Testing for HER2 status is critical in determining the appropriate treatment, as HER2-positive cancers may respond to specific targeted therapies, such as trastuzumab (Herceptin).

• HER2-Positive Breast Cancer:

  • Tends to be more aggressive and fast-growing.
  • Higher risk of recurrence.
  • Can be treated with HER2-targeted therapies (e.g., trastuzumab, pertuzumab, lapatinib).

• HER2-Negative Breast Cancer:

  • May not be as aggressive.
  • Does not benefit from HER2-targeted therapies but may be treated with other forms of chemotherapy, hormone therapy, or radiation.

Normal Range and Interpretation

• Normal (HER2-Negative):
  • IHC score of 0 or 1+, or FISH/ISH showing no gene amplification.
  • Indicates that the HER2 gene is not overexpressed or amplified, and the cancer is less likely to respond to HER2-targeted therapies.
• Borderline (Equivocal):
  • IHC score of 2+.
  • Requires further testing with FISH or ISH to confirm HER2 status.
• Abnormal (HER2-Positive):
  • IHC score of 3+, or positive FISH/ISH results.
  • Indicates that the HER2 gene is overexpressed or amplified, and the cancer may be treated with HER2-targeted therapies.

Normal Range and Interpretation

• Normal (HER2-Negative):
  • IHC score of 0 or 1+, or FISH/ISH showing no gene amplification.
  • Indicates that the HER2 gene is not overexpressed or amplified, and the cancer is less likely to respond to HER2-targeted therapies.
• Borderline (Equivocal):
  • IHC score of 2+.
  • Requires further testing with FISH or ISH to confirm HER2 status.
• Abnormal (HER2-Positive):
  • IHC score of 3+, or positive FISH/ISH results.
  • Indicates that the HER2 gene is overexpressed or amplified, and the cancer may be treated with HER2-targeted therapies.

Sample Type

• Tissue Sample: The most common sample type is a tissue biopsy from the tumor. This can be taken during surgery, a core needle biopsy, or a fine needle aspiration.
• Blood Sample: In some cases, a blood sample might be used to detect circulating tumor DNA (ctDNA) or circulating tumor cells (CTCs) that carry HER2 amplifications.