HER2/neu is found amplified in breast, ovarian, and tumors of the gastrointestinal tract. Increased amplification of the HER2/neu gene correlates with decreased response to hormonal therapy in breast cancer. HER2/neu has strong prognostic value in breast cancer, and correlates with increased tumor size, positivity in adjacent lymph nodes, and higher grading scores with likelihood of metastases.
HER2/neu analysis may be performed on suspicious or representative tissue samples using immunohistochemical (IHC) techniques. HER2/neu is also released into the blood, and as such, may be identified and quantified in plasma samples using commercially available immunoassay methods.2