Specific gaps in available test methods for mechanisms associated with breast cancer include progesterone receptor binding (Brisken 2013) and transcriptional activation (Faivre et al. 2008; Kougioumtzi et al. 2014), Her2 activation (Stern 2008), ERβ activity (Pearce and Jordan 2004), and DNA repair mechanisms (Barnes and Camplejohn 1996). Here, ESR2 is linked to breast cancer.