Breast cancer is a major health problem with close to two million new cases diagnosed each year worldwide. In about 1 out of 5 cases, human epidermal growth factor receptor 2 (HER2) has been found to be overexpressed. HER2 is a membrane receptor that is required for normal development of many tissues, including breast, ovary, lung, liver, kidney and those of the central nervous system. However, when overexpressed, HER2 can result in more aggressive forms of cancer and decreased patient survival. In addition to its role in breast cancer, HER2 overexpression is also known to occur in other forms of cancer, e.g., ovarian, stomach, lung and uterine cancers.