What does HER2-positive mean in breast cancer?

HER2-positive in breast cancer indicates that the cancer cells have a higher than normal amount of the HER2 protein, which is a growth factor receptor involved in cell signaling and growth. This overexpression of the HER2 protein can lead to more aggressive tumor behavior and is associated with a specific type of breast cancer that can respond to targeted therapies, such as trastuzumab (Herceptin). In this context, the identification of excessive HER2 protein levels is crucial because it influences treatment options and prognostic outcomes.

Understanding that HER2-positive tumors can behave differently than HER2-negative ones allows healthcare providers to tailor treatments effectively, making it a vital concept in breast cancer management. The other choices do not accurately represent HER2-positive status, as normal levels of HER2, absence of HER2 protein, or estrogen receptor positivity alone do not define this subtype of breast cancer.