- Non-metastatic primary invasive adenocarcinoma of the breast clinical stage I to IIIC, including inflammatory and multicentric/multifocal breast cancer, with tumor size ≥1 centimeter (cm) by ultrasound or ≥2 cm by palpation, centrally confirmed HER2-positive (immunohistochemical score [IHC] 3+ or in situ hybridization [ISH]-positive)