This multicenter, non-randomized, open-label, phase 2 study is designed to evaluate the safety and efficacy of pertuzumab (Perjeta) in combination with trastuzumab (Herceptin) and anthracycline-based chemotherapy as neoadjuvant treatment in participants with HER2-positive locally advanced, inflammatory, or early-stage breast cancer. Each investigator will choose a treatment regimen (A or B) for all of their participants to follow. Treatment regimen A (for Cohort A) will include dose-dense doxorubicin and cyclophosphamide (ddAC), followed by paclitaxel, with pertuzumab and trastuzumab given from the start of paclitaxel. Treatment regimen B (for Cohort B) will include 5-fluorouracil, epirubicin, and cyclophosphamide (FEC), followed by docetaxel, with pertuzumab and trastuzumab given from the start of docetaxel. Participants in both cohorts will subsequently undergo surgical treatment and then resume pertuzumab and trastuzumab treatment.