Studies of early carcinogenesis suggest that epigenetic changes, in addition to genetic ones, contribute to tumor initiation. DNA methylation, defined as the covalent addition of a methyl group to cytosine residues within cytosine-phosphate-guanine (CpG) dinucleotides, is heavily involved in the regulation of gene activation and has been proposed as a potential biomarker for the early detection of breast cancer owing to the reversible nature of epigenetic modifications. The ultimate goal of this work was the identification of CpG sites that most strongly characterize the “early field defect”, under the field cancerization hypothesis, according to which tissue adjacent to the tumor lesion, although apparently normal, may exhibit early epigenetic alterations.