With the developmentof trastuzumab, a monoclonal antibody against HER2, major advanceshave been made in systemic therapy for this breast cancer subtype.1,4−6 The remaining 10–15% of breast cancers aredefined by the absence of these three markers and are therefore referredto as triple-negative breast cancer (TNBC), which has the most unfavorableprognosis and an increased risk of recurrence. The gene discussed is ERBB2; the disease is breast cancer.