Evidence has been growing to support the correlation between MAO-A isoenzyme and many types of cancer, including prostate cancer [2, 10–13], hepatocellular carcinoma [14, 15], brain tumor (gliomas) [16], classical Hodgkin's lymphoma [17], colorectal cancer [18], lung cancer [19–21], and breast cancer [22]. The gene discussed is MAOA; the disease is breast cancer.