We reported, here, the first data on the effects of garlic, particularly of diallyl disulfide (DADS), one of its most bioactive compounds, on breast tumor cells expressing HER2, to fill the knowledge gap and to establish the potential usefulness of garlic derivatives in a breast cancer phenotype which, despite the significant progresses made in recent years, presents some important critical issues. The gene discussed is ERBB2; the disease is breast neoplasm.