Hypermethylation of the RASSF1A gene is a prime candidate among many genes as a potential novel biomarker for stage I–IV breast cancer and have been investigated for early detection of cancer, diagnosis, prognosis for the patient, prediction of the effect of therapy, and monitoring of the effect of therapy by measuring the circulating biomarker concentration (reviewed in [9]). The gene discussed is RASSF1; the disease is cancer.