Breast-conserving surgery, a major achievement in surgical oncology, has allowed an increasing number of breast cancer patients to avoid the mutilation of mastectomy. However, mastectomy still is performed in certain circumstances although breast-conserving surgery would be equally safe. Many reasons, including patients' and surgeons' personal motivations, influence the decision-making process before the final choice between breast preservation and mastectomy. The importance of quality measurement and reporting in medicine is increasingly recognized, and breast surgery is no exception. The substantial variability of re-excision rates for positive surgical margins after a first attempt at breast-conserving surgery suggests that improvement is possible. Therefore, the re-excision rate has been proposed as a quality metric for assessing and comparing the performance of different institutions. Indeed, re-excision rates can be reduced by actionable factors such as accurate preoperative local staging, localization of occult lesions, and intraoperative assessment of the oriented specimen. However, equally important non-actionable risk factors pertaining the biology, detectability, and resectability of the tumor also should be taken into account. Therefore, if the re-excision rate has to be used as a performance indicator of breast surgical care, critical interpretation of results with accurate case-mix adjustment are mandatory, and reasonable targets must be appropriately set so that surgeons treating patients at higher risk of positive margins are not unduly penalized.