ERBB2 and breast cancer: The treatment landscape of both early and advanced HER2-positive breast cancer has extensively changed over the past 20 years, with a rapidly expanding number of anti-HER2 therapeutics, including increasingly selective small molecule inhibitors, potent antibody-drug conjugates (ADCs), and bispecific antibodies, which have enriched our drug armamentarium and improved the survival for patients with HER2-positive advanced breast cancer (ABC).