By determining the methylation status of the promoter region of eleven genes including ABCB1 in 27 ductal carcinoma in situ (DCIS), 28 small IDCs, 34 IDCs with a DCIS component, and 28 normal breast tissue samples, ABCB1 promoter methylation was as frequently detected in DCIS, a non-invasive lesion of the breast, as in early invasive breast cancer [141]. This evidence concerns the gene ABCB1 and invasive breast carcinoma.