Tolerability and Efficacy of Adjuvant T-DM1 in Patients with HER2 Positive Breast Cancer After Incomplete Pathological Response to Neoadjuvant Chemotherapy Including Anti-HER2 Agents.

Inclusion Criteria: * Histological diagnosis of HER2 positive breast cancer; * Presence of invasive residual disease on T or N after neoadjuvant chemotherapy including anti-HER2 agents * Treatment with T-DM1 in the adjuvant post-neoadjuvant setting, in case of positive hormone receptors in combination with adjuvant hormone therapy. Complementary radiotherapy will be allowed as per lines guide; * Availability of adequate information regarding treatment with adjuvant T-DM1 in accordance with the objectives of the study; * Written informed consent for the prospective part and, if possible, for the recruited patients retrospectively Exclusion Criteria: * Concomitant treatments with other biological agents; * Absence of clinical data that allow the correct analysis of the primary and secondary objectives; * Patients with a history of other malignant neoplasms; * Contraindications to the use of T-DM