Intraoperative ultrasound guidance for palpable breast cancer excision (COBALT trial): a multicentre, randomised controlled trial.

Background: Breast-conserving surgery for palpable breast cancer is associated with tumour-involved margins in up to 41% of cases and excessively large excision volumes. Ultrasound-guided surgery has the potential to resolve both of these problems, thereby improving surgical accuracy for palpable breast cancer. We aimed to compare ultrasound-guided surgery with the standard for palpable breast cancer-palpation-guided surgery-with respect to margin status and extent of healthy breast tissue resection.