Surgical resection of breast cancers: Molecular analysis of cancer stem cells in residual disease.

Background: Approximately 70% of breast cancer patients have residual disease after neoadjuvant chemotherapy. This study was designed to determine whether breast cancer cells with stemlike properties are present in residual disease after neoadjuvant chemotherapy and whether they exhibit oncogenic mutations. The presence of breast cancer cells with stemlike properties with specific mutations may help explain the poor prognosis associated with residual disease.