ERBB2 and breast cancer: Although NCCN guideline recommended chemotherapy with anti‐HER2 agent for all T1a‐T1c patients, it also claimed that the prognosis of this patient group remained elusive.22 The present study retrospectively analyzed the BCSS and OS for HER2+/HoR‐ T1a‐T1c breast cancer and proved that T1a had similar outcome with T1b, and both T1a and T1b were superior to T1c, which implied 1.0 cm may be a better option for T1 subclassification.