Remarkably, in group 2 patients among all evaluated HER dimers, the most prevalent was the HER-1:HER-3 heterodimer, which probably represents a percentage of HER-2 negative breast tumors that may bear the potential to show growth inhibition and hence clinical benefit with HER-3-directed agents (Figures 6 and 7). Here, ERBB3 is linked to breast neoplasm.