An aberrancy of the HER family of receptors that has been well documented is its key role in tumorigenesis, with HER2 amplification or overexpression being implicated in various types of cancer including breast cancer, gastric/gastroesophageal cancer, ovarian cancer, colorectal cancer, lung cancer, bladder cancer, and head/neck cancer [74]. The gene discussed is ERBB2; the disease is breast cancer.