Inclusion Criteria:  Female breast cancer patients aged 18-75 years. ECOG performance status of 0 to 1; Known hormone receptor status; HER2 positive breast cance at any stage; breast cancer Patients are about to receive pyrotinib monotherapy or combined chemotherapy； Patients with adequate organ function before enrollment (no blood transfusion, no white blood cell or platelet-elevating drugs used within 2 weeks before screening): 1) Blood routine:ANC≥1.5×10^9/L; PLT≥90×10^9/L; Hb≥90 g/L；2)Blood biochemistry: TBIL≤1.5×ULN;ALT and AST ≤1.5×ULN; alkaline phosphatase ≤ 2.5×ULN; BUN and Cr≤1.5×ULN；3) Cardiac color Doppler ultrasound:LVEF≥55%；4) 12-lead ECG: QTcF < 470 msec; Signed the informed consent form prior to patient entry, and have good compliance and are willing to cooperate with follow-up.  Exclusion Criteria:  patients with Severe heart disease or discomfor; Previous or ongoing use of HER2-targeted tyrosine kinase inhibitors ; Inability to swallow, intestinal obstruction, or other factors that affect the taking and absorption of the drug; Allergy to pyrotinib; history of immunodeficiency, including HIV positive, active HBV/HCV, other acquired or congenital immunodeficiency disease and organ transplantation history; Patients during pregnancy or lactation, patients with childbearing potential tested positive in baseline pregnancy test, or patients unwilling to take effective contraceptive measures throughout the trial and 7 months after the last study medication; patients with intestinal disease, serious concomitant diseases, or other comorbid diseases that will interfere with the planned treatment, or patients not eligible for this study judged by the investigator.