Generation of Heart Muscle Cells From Blood or Skin Cells of Breast Cancer Patients

Inclusion Criteria:

* Female
* Age greater than 18 years
* Willing to participate in protocol procedures with signed informed consent
* Assessment of LVEE via echocardiogram, cardiac MRI, or MUGA

Subjects in the cardiotoxicity group (TOX) must meet the following criteria:

* History of HER2 positive breast cancer (stage I-IV)
* Prior/current treatment with anthracycline based chemotherapy followed by anti-HER2 directed therapy or anti-HER2 directed therapy alone
* Assessment of LVEF at baseline prior to initiation of anthracycline or anti-HER2 therapy and during anti-HER2 therapy via echocardiogram, cardiac MRI, or MUGA
* Prior confirmed diagnosis of cardiotoxicity associated with anti-HER2 based therapy, defined as a decrease in LVEF \> 10% from baseline to \< 53% with symptoms of heart failure (NYHA class II-IV).

Subjects in the no cardiotoxicity group (NO-TOX) must meet the following criteria:

* History of HER2 positive breast cancer (stage I-IV)
* Completion of planned anthracycline and anti-HER2 therapy, or anti-HER2 therapy alone
* No symptoms of heart failure (NYHA class II-IV) during and at the end of anthracycline and anti-HER2 therapy
* Assessment of LVEF at baseline prior to innitiation of anthracycline or anti-HER2 therapy and during anti-HER2 therapy via echocardiogram, cardiac MRI, or MUGA
* Normal LVEF \>53% at each assessment during and at the end of trastuzumab therapy.
* Maximum absolute decrease in LVEF \<5% from baseline during and at the end of trastuzumab therapy.
* LVEF assessment performed at baseline and at least two time points during trastuzumab therapy.

Exclusion Criteria:

* Unwilling or unable to give skin biopsies
* Contraindications to punch biopsy including but not limited to bleeding diathesis, as determined by the investigator.
* Known pre-existing CV disease prior to initiation of breast cancer therapy as determined by the investigator, including

  * Obstructive coronary artery disease (stenosis \>70%)
  * Arrhythmia - paroxysmal or persistent atrial arrhythmias, sustained ventricular tachycardia (\>30 seconds), ventricular fibrillation, or cardiac arrest
  * Cardiomyopathy (EF \<53%)
  * Heart failure (NYHA class II-IV)
  * Valvular heart disease with equal to or greater than moderate stenosis or regurgitation