An immunohistochemistry test is administered to breast cancer tissue that has been extracted via a biopsy. The test helps conclude if the cancer cells have a HER2 receptor on the surface. This is done by selectively imaging antigens in a cell tissue, by harnessing the propensity of antibodies to bind specifically with antigens in biological tissues.

This test is also employed for hormone receptor testing. The presence of hormone receptors underlines the cause of the cancer cells fueled by hormones estrogen and/or progesterone.