ESR1 and breast cancer: A 40-year-old woman with a history of Hodgkin lymphoma treated with ABVD chemotherapy (doxorubicin 300 mg/m2, bleomycin, vinblastine, and dacarbazine) and mantle radiation at 19 years of age presents with a stage IIB (T2N1) lymph node–positive ER−/HER2+ breast cancer.