ERBB2 and testicular cancer: Mutation in this gene is well known as a cause of PTEN mutations that may overlap with other mutations, including human epidermal growth factor receptor 2 (HER2) and loss of a single PTEN allele has been shown to accelerate tumorigenesis in HER2-overexpressing breast tumors, Peutz–Jeghers syndrome, as well as with skin, pancreatic, and testicular cancers.