This Non-Interventional Study will describe and analyze the clinical use of pyrotinib in clinical practice in the treatment of HER2 positive breast cancer in the real world.

Inclusion Criteria:

1. ≥18 years old with histologically confirmed HER2 positive breast cancer.
2. Documented HER2 overexpression by local laboratory ,defined as immunohistochemistry (IHC) 3+ or fluorescence in situ hybridization (FISH) positive.
3. Physician has determined that treatment with pyrotinib is indicated.
4. Traceable medical record available.

Exclusion Criteria:

1. Patients who are unable to understand the nature of the study and are unwilling to sign an informed consent .
2. Pregnant or breast feeding patients
3. Patients participating in any interventional clinical trial that includes investigational or marketed products at the time of enrollment.
4. Patients not suitable for this study under investigators' consideration.

HER2+ breast cancer patients whose treatment decision with pyrotinib has been made by their physician and who meet the eligibility criteria will be invited to participate in the study