Her-2/neu Testing

Her-2/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 Her-2/neu gene and produce low levels of the Her-2 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 Her-2/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). Tumors that have this over-expression tend to grow more aggressively and resist hormonal therapy and some chemotherapies, and patients generally have a poorer prognosis.

There are two main ways to test Her-2/neu status: immunohistochemistry (IHC) and fluorescent in situ hybridization (FISH). IHC measures the amount of Her-2/neu protein present. FISH looks at the genetic level for actual gene amplification the number of copies of the gene present. IHC is currently the most widely used initial testing method; however, if it is indeterminate or negative, then the FISH method is often done as a follow-up test.


A sample of breast cancer tissue is obtained by doing a fine needle aspiration, needle biopsy, or surgical biopsy. Her-2/neu protein sometimes is measured in a blood sample, drawn from a vein in the arm. The amount of Her-2/neu protein present in serum is loosely associated with the amount of cancer present. However it will not be positive until the tumor is fairly big and is not widely used for determining Her-2/neu status.


DNA Ploidy

  • Aneuploid is unfavorable

  • Diploid is favorable

S-phase Fraction

  • Greater than 5.5% is unfavorable

  • Less than 5.5% is favorable

HER 2 Protein

  • Moderate or strong staining in 10% of the cancer cells is unfavorable

  • Partial staining in £10% of the cancer cells is favorable

Cathepsin D

  • Greater than 10% is unfavorable

  • Less than 10% is favorable

p53 Protein

  • Greater than 10% is unfavorable

  • Less than 10% is favorable

Ki67 Protein

  • Greater than 20% is unfavorable

  • 10%-20% is borderline

  • Less than 20% is favorable

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and wether your values are considered within normal limits.


Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.


It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.