HER2 Testing Information | What Your Test Results Mean

Breast Cancer Test Results

To classify exactly what kind of breast cancer you have, your doctor may take a biopsy of your tumor, which is a sample taken from the tumor either during surgery or using a needle. That sample tissue is then studied in a lab to determine exactly what kind of tumor it is. Tests are done to look for different substances in the tumor, and each test result is assigned a status, such as positive or negative. The results are called your pathology report.

Knowing the biological makeup of the tumor helps the doctor understand how quickly the cancer might grow and what treatments may be best.

For breast cancer, a doctor wants to know a cancer's hormone receptor status and HER2 status. Hormones such as estrogen and progesterone play a role in many breast cancers, and it is important to know whether a tumor is positive or negative for either of these hormone receptors. An estrogen-receptor-positive tumor is called "ER+", and a progesterone-receptor-positive tumor is called "PR+". Tumors that are positive for either of these hormone receptors may benefit from hormonal therapy.

Similarly, HER2 status can tell a lot about how aggressive the breast cancer is, as well as what treatments may provide the most benefit. HER2 status and hormone-receptor status are not the same thing, and being positive for one does not mean the cancer is positive for the other. Again, knowing what kind of cancer you have is critical to deciding what the best course of treatment will be.

Accurate testing is important; your pathology report may contain inconclusive results. Sometimes one test may not be enough to determine with certainty whether your tumor is HER2+. Ask your doctor to discuss the results of your pathology report, explain how your tumor's HER2 status was determined, and to let you know whether another test may be necessary.