Hello, this is Nurse Home Fit, here to help you recover your daily life. Today, we will learn about one of the types of breast cancer, HER2. What is HER2? HER2 is a protein located on the surface of cells that helps regulate cell growth and division.While it exists in normal cells, in some breast cancers, HER2 is overexpressed, which promotes the growth of cancer cells.This type is called HER..