HER2-positive breast cancer is a type of breast cancer where cancer cells have higher levels of the human epidermal growth factor receptor 2 (HER2) protein. Stage 1 HER2-Positive Breast Cancer TreatmentPatients with stage 1 HER2-positive breast cancer often have small tumors that have not spread to lymph nodes. Stage 2 HER2-Positive Breast Cancer TreatmentStage 2 tumors are larger or involve nearby lymph nodes. Stage 3 HER2-Positive Breast Cancer TreatmentStage 3 is locally advanced cancer that may involve multiple lymph nodes or nearby structures. Metastatic HER2-Positive Breast Cancer TreatmentMetastatic cancer has spread beyond the breast to other organs.