This study will evaluate the safety and efficacy of neoadjuvant trastuzumab, pertuzumab and chemotherapy chosen by the investigators and identify the molecular characterization and subtypes in human epidermal growth factor receptor 2 (HER2)-positive breast cancer.

Inclusion Criteria:

1. Age 18 - 75 years;
2. Eastern Cooperative Oncology Group (ECOG) score status 0-1.
3. Histologically confirmed invasive breast carcinoma with a primary tumor size of more than (>) 2 centimeters (cm) by standard local assessment technique; Breast cancer stage at presentation: early-stage (T2-3, N0-1, M0) or locally advanced (T2-3, N2 or N3, M0; T4, any N, M0);
4. HER2-positive breast cancer confirmed by immunohistochemistry or HER2 gene amplification by in situ hybridization;
5. Known estrogen receptor (ER) and progesterone receptor (PgR) status.
6. Has adequate bone marrow, renal, hepatic and blood clotting functions.
7. Left ventricular ejection fraction (LVEF) ≥50 percent (%).
8. Women of childbearing potential and men with partners of childbearing potential must agree to use a highly effective form of contraception or avoid intercourse during and upon completion of the study and after the last dose for at least 7 months. Negative serum or urine pregnancy test within 7 days before study enrollment.
9. Willing to provide tissue for research purposes.
10. Volunteer to participate in this study and sign the informed consent.

Exclusion Criteria:

1. Patients with stage IV metastatic breast cancer.
2. Bilateral invasive breast cancer;
3. Patients with breast cancer who have previously received anti-tumor therapy.
4. Occurred or present with other malignant tumors within 5 years. Patients with the following two conditions can be enrolled: other malignancies treated with a single operation, achieving continuous 5-year disease-free survival (DFS); Cured cervical carcinoma in situ, non-melanoma skin cancer and superficial bladder tumors [Ta (non-invasive tumor), Tis (cancer in situ) and T1 (tumor infiltrating basal membrane)];
5. Subjects had participated in clinical trials of other antineoplastic drugs within 4 weeks before the group;
6. Has uncontrolled or significant cardiovascular disease.
7. Allergy to any investigational drug or any ingredient or excipient in the drug;
8. Female subjects who are pregnant, lactating or plan to become pregnant during the study.
9. Has any other condition that per protocol or in the opinion of the investigator is inappropriate for the study.