Personalizing extent of breast cancer surgery according to molecular subtypes.

The molecular subtype of breast cancer is the major determinant of the type of systemic therapy, but less attention has been paid to the impact of subtype on local therapy outcomes. Presenting features of breast cancer vary with hormone receptor status, with triple negative cancers being significantly less likely than hormone receptor positive cancers to have nodal metastases, and HER2 overexpressing cancers being more likely to be multifocal or multicentric and to have an extensive intraductal component. The risk of local recurrence varies with subtype as well, with triple negative cancers having the highest risk of local recurrence after both breast-conserving therapy and mastectomy, indicating that bigger surgery does not overcome bad biology.