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Anatomic Pathology


1.    What are  ER, PR, and HER2/neu?

·         “ER” AND “PR” are short for estrogen receptors and progesterone receptors. These are proteins found in some cancers cells.  When hormones (estrogen and progesterone) attach to these receptors, they make cancer cells grow.

·         “HER2” is short  for  human epidermal growth factor receptor 2 gene ERBB2. It also has several names like c-erb and Her2/neu. It  is a protein that appears on the surface of some breast cancer cells. It is an important part of the cellular pathway for growth and survival.

2.    What is their role of the HORMONE RECEPTORS (ER, PR) AND HER 2 RECEPTORS in breast cancer treatment?

Testing for hormone receptors  and Her2 receptor  is important because the results help guide your doctor decide whether the cancer is likely to respond to hormonal therapy or other treatments.


o    If your tumor is ER positive and/or PR positive, the cancer cells have many hormone receptors.  Treatments that prevent these cells from getting the hormones they need to grow (hormone therapies, such as tamoxifen or aromatase inhibitors) may stop tumor growth.

o     If your tumor  is ER negative and/or PR negative, then hormonal therapy is unlikely to work and your doctor will choose other treatments.


o     If your tumor is HER2-positive (HER2+), there are  many HER2 genes inside the cancer cells (also called HER2 over-expression) and a large amount of HER2 proteins on the surface of these cells. The cancer cells make an excess of HER2 protein because of gene mutation.

o    If your tumor is HER2- negative (HER2-) cancer cells have few HER2/neu genes and little or no HER2 protein on the surface of these cells.

o    HER2 positive breast cancers tend to be more aggressive than other tumors. They're also less responsive to hormone treatment. Treatments that specifically target HER2 are very effective, which include trastuzumab, lapatinib, and other  newly developed medications

3.    How are ER, PR, and Her2 testing done in the lab?

IHC, or ImmunoHistoChemistry, is a special staining process performed on breast cancer tissue removed during biopsy. IHC is used to show whether or not the cancer cells have hormone receptors and HER2 receptors on their surface. If your IHC HER2 test results are negative or borderline, an In Situ Hybridization (ISH) test is recommended, which uses a different technology to measure  HER2 status.

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