DAB (brown) chromogen localized to cell membrane in HER2 stain using clone CB11. Counterstain is hematoxylin.
Each antibody used with IHC has a specific target and staining pattern. The specific location where the precipitation of the chromogen (colored end product) occurs is frequently referred to as its localization or staining pattern. The staining pattern and intensity of reaction is assessed within the context of the tissue morphology, only by a qualified pathologist. As examples of stain localization, both estrogen receptor (ER) and progesterone receptor (PR) are localized within the nucleus. HER2 antibody is localized with the cell membrane and is described as a membranous stain