This study investigated methylation status of seven imprinted differentially methylated regions—PLAGL1/ZAC1, H19-ICR1, IGF2-DMR2, KvDMR-ICR2, RB1, SNRPN-DMR1 and PEG3—in blood samples from 189 women with the most common type of invasive breast cancer (invasive ductal carcinoma—IDC), 41 women with in situ breast cancer (ductal carcinoma in situ—DCIS) and 363 matched disease-free controls. This evidence concerns the gene RB1 and breast carcinoma in situ.