In addition, ER positive breast cancer types exhibit favorable responses to hormone therapy (Althuis et al., 2004; Foulkes, Smith & Reis-Filho, 2010; Thrane et al., 2013), for example tamoxifen (Ramirez-Ardila et al., 2013), or aromatase inhibitors (Hiscox, Davies & Barrett-Lee, 2009), designed to block aberrant signaling within oncogenic pathways. The gene discussed is ESR1; the disease is breast cancer.