ERBB2 and breast cancer: There were no regional recurrences after a median follow-up of 27 months.<h4>Conclusion</h4>In this retrospective cohort of clinically node-negative, hormone receptor-positive, HER2-negative cT1-3 breast cancer patients undergoing upfront mastectomy, omission of intraoperative frozen section (IFS) analysis was not associated with early regional recurrence during the observed follow-up.