HER2-positive tumors account for about 20–30% breast cancer [4], 20% advanced gastric or gastric or gastro-esophageal junction cancers [5], 5–15% bladder cancers [6], 5–15% cervix cancers [7], 12–15% gallbladder cancers [8], 8–35% endometrium cancers [9], 6–7% ovarian cancers [10], and 15–37% salivary duct cancers [11]. The gene discussed is ERBB2; the disease is breast carcinoma.