A protein involved in normal cell growth. It is found on some types of cancer cells, including breast and ovarian. Cancer cells removed from the body may be tested for the presence of c-erbB-2 to help decide the best type of treatment. c-erbB-2 is a type of receptor tyrosine kinase. Also called HER2/neu, human EGF receptor 2, and human epidermal growth factor receptor 2.