A total of 60 mammary tumor samples of rat mammary carcinomas (from three experimental groups) were evaluated to analyze the methylation status of five gene promoters: ATM including four evaluated CpG (cytosine-phosphate-guanine) sites (CpG 1–4), PITX2 (CpG 1–5), RASSF1 (CpG 1–3), PTEN (CpG 1–6), and TIMP3 (CpG 1–6) (Figure 7). The gene discussed is PTEN; the disease is breast carcinoma.