While HER2 is involved in the disease pathogenesis of HER2-expressing breast carcinoma [53,54], the extent of oncogene addiction to HER2 alterations can vary on the basis of the type of genetic alteration, with oncogenes arising from gene fusions often present with the highest level of oncogene addiction, followed by other mutations [20,50]. Here, ERBB2 is linked to breast carcinoma.