ERBB2 and breast carcinoma: In addition, we assessed whether low HER2 expression is associated with distinct clinicopathological characteristics and prognosis in our series.<h4>Methods</h4>We conducted a retrospective study that included 500 patients diagnosed with stage I-III HR+/HER2- breast cancer who underwent surgery and had Oncotype DX recurrence score determined between 2009 and 2023 at Hospital Clínico San Carlos, Madrid, Spain.