ESR1 and neoplasm: To study the association between the number of shared mutations and tumor characteristics we collected relevant data from the histopathology reports, including data on tumor type (lobular or ductal), size, grade (according to Elston-Ellis), lymph node status, estrogen and progesterone receptor (ER and PR) status, presence of HER2 amplification and proliferation (Ki-67/MIB1).