Marked differences have been noted in long-term breast cancer related outcomes according to disease subtype, including significantly worse recurrence rates and overall survival in those patients with Her2 positive tumors and tumors that lack expression of ER, PR and Her2 (triple negative) (Sorlie et al. 2001, 2003; Carey et al. 2006; Slamon et al. 1987; Ravidn and Chamness 1995). The gene discussed is ESR1; the disease is breast cancer.