Changing frequency of equivocal HER-2/neu scores and factors predictive of negative HER 2/neu fluorescent in situ hybridisation in invasive carcinomas of the breast.

Background: Analysis of human epidermal growth factor receptor 2 (HER-2) status has become standard of care in breast cancer patients due to its important prognostic and therapeutic implications. Immunohistochemistry (IHC) is the most commonly used primary method for detection of HER-2 overexpression. Controversy exists on the interpretation of samples that are equivocal for HER 2 status (IHC 2+).