From the aforementioned clinical and molecular analyses, we propose the following five critical markers for a new DCIS classification approach: age <45 years, HER2 amplification, GATA3 mutation or downregulation, PgR protein negativity (for high-risk and true DCIS), and PIK3CA mutation positivity (for false DCIS). The gene discussed is PGR; the disease is ductal breast carcinoma in situ.