We next examined the data to identify any correlation between the recurrent aUPD regions of diverse clinical parameters (including ER, PR and HER2/neu status, grade, lobular or ductal subtype and invasive or infiltrating cancer), and characterized by a distinct aUPD profile and whether specific aUPD regions in each group of tumors harbor narrow regions of aUPD that indicate regions harboring homozygous mutation that may be used as a marker or a therapeutic target in each group of breast cancer. This evidence concerns the gene ESR1 and breast cancer.