Breast-Conserving Surgery in Multicentric Breast Cancer: Evolving Evidence and Patient Selection.

Multicentric breast cancer-two or more biopsy-proven tumor foci in anatomically distinct regions of the same breast-has historically been treated as a near-automatic indication for mastectomy, reflecting concerns about occult residual disease, achievability of negative margins at every focus, and unacceptable cosmetic outcome. This narrative review synthesizes the evidence underlying that historical position and the more recent data that have begun to qualify it. The single-arm ACOSOG Z11102 (Alliance) trial reported a 5-year local recurrence rate of 3.1% after breast-conserving therapy for two to three ipsilateral foci and recent retrospective cohorts report comparable to local control. These findings sit alongside a persistent and unresolved tension around preoperative MRI, which improves detection of additional foci but has not demonstrated improvement in local control or survival outcomes in randomized trials, despite increasing mastectomy conversion. We review the definitions and biology of multifocal and multicentric disease, the maturing role of oncoplastic technique, margin and radiotherapy planning considerations specific to multicentric resection, the evolving use of neoadjuvant systemic therapy, hereditary cancer considerations, and the current guideline landscape (ASBrS, NCCN, ESMO, AGO). We propose a practical, multidisciplinary framework for patient selection and identify the principal gaps-absence of randomized comparison with mastectomy, unresolved necessity of routine MRI, and limited data on breast conservation after neoadjuvant therapy specifically in multicentric disease-that should guide both clinical decision-making and future research.