Tanjina Kader, PhD, Peter MacCallum Cancer Centre, Melbourne, Australia, relates how molecular analysis of de novo primary tumors in ductal carcinoma in situ (DCIS) could have serious clinical implications for some patients. A recent study has found that 18% of de novo DCIS tumors analyzed were nonclonal and not significantly associated with common prognostic biomarkers. These patients require different treatment regimes including endocrine therapy, bilateral mastectomy, or genetic counseling. Currently, it is common practice to treat all recurrent DCIS with surgery or radiotherapy. This interview took place at the American Association for Cancer Research Annual Meeting in New Orleans, LA.