A high mitotic score in breast cancer after neoadjuvant chemotherapy is predictive of outcome and associated with a distinct morphology.

High post-NAC mitotic score breast cancers cause high morbidity and mortality, frequently have pushing borders and zones of necrosis, and may show loss of common 'breast cancer markers'. Our findings support that necrosis in pretreatment studies and post-NAC mitotic score should be routinely reported, as they offer significant additional prognostic information to guide management.