Evaluation of HER2DX Assay on Treatment Decisions in Patients With Early Stage HER2+ Breast Cancer: the HER2BREASTDX

Inclusion Criteria: * Patients ≥ 18 years of age; * Histologically confirmed HER2+ breast cancer; * Stage I-III breast cancer without evidence of distant metastases; * Being candidate to neoadjuvant/adjuvant therapy and locoregional treatment (surgery +/- radiotherapy); * Written informed consent, signed by the patient, to study-specific procedures (the consent will consist of 2 levels: level 1 specifically for patients enrolled in the primary endpoint cohort and level 2 for all patients); Exclusion Criteria: * HER2- BC; * Stage IV breast cancer; * Lack of informed consent because of patient's incapable of discernment or unwilling to participate;