Breast cancers with HER2 gene amplification or HER2 protein overexpression are called HER2-positive in the pathology report. HER2-positive breast cancers tend to grow faster and are more likely to spread and come back compared to HER2-negative breast cancers. But there are medicines specifically for HER2-positive breast cancers.
ER positive means the tumor feeds on estrogen and PR positive means the tumor feeds on progesterone. These tumors are treated with hormone suppression drugs like Tamoxifen. If your hormones are suppressed, the ER+ and/or PR+ tumor has nothing to feed on and thus, it improves your chances of having the cancer NOT come back.