ESR1 and breast cancer: Transcriptomic analyses stratified profiles from HN tissues adjacent to breast cancer or ductal carcinoma in situ (DCIS) data into two extratumoral subtypes: active and inactive, with the active subtype significantly associated with overall survival in estrogen receptor (ER)‐positive patients (HR 2.5, p = 0.062) and hormone‐treated patients (HR 2.6, p = 0.045)