Prediction of Pathologic Complete Response by Multiple Core Needle Biopsy or Vacuum Assisted Biopsy Before Surgery in Breast Cancer With Complete Clinical Response After Neoadjuvant Chemotherapy.

Breast cancer patients who received neoadjuvant chemotherapy and is predicted to have achieved pathologic complete response (pCR) on MRI will enrolled. The enrolled patients will undergo either US-guided multiple core needle biopsy or US-guided vacuum-assisted biopsy of the tumor bed where it had been marked with an indicator (clip). The patient will undergo subsequent wide excision of the tumor bed. Histopathologic findings of the biopsy and the surgical specimen will be compared for pCR, and the ability of preoperative biopsies to predict pCR will be evaluated.