in tumors that express other tyrosine kinases, most notably KIT. Most gastrointestinal stromal tumors express KIT, which can be detected by immunohistochemistry. Monoclonal antibodies Many proteins shown to be highly upregulated in pathological states by immunohistochemistry are potential targets for therapies utilising monoclonal antibodies. Monoclonal antibodies, due to their size, are utilized against cell surface targets. Among the overexpressed targets are members of the EGFR family, transmembrane proteins with an extracellular receptor domain regulating an intracellular tyrosine kinase. Of these, HER2/neu (also known as Erb-B2) was the first to be developed. The molecule is highly expressed in a variety of cancer cell types, most notably breast cancer. As such, antibodies against HER2/neu have been FDA approved for clinical treatment of cancer under the drug name Herceptin. There are commercially available immunohistochemical tests, Dako HercepTest, Leica Biosystems Oracle and Ventana Pathway. Similarly, EGFR (HER-1) is overexpressed in a variety of cancers including head and neck and colon. Immunohistochemistry is used to determine patients who may benefit from therapeutic antibodies such as Erbitux (cetuximab). Commercial systems to detect EGFR by immunohistochemistry include the Dako pharmDx. Mapping protein expression Immunohistochemistry can also be used for a more general protein profiling, provided the availability of antibodies validated for immunohistochemistry. The Human Protein Atlas displays a map of protein expression in normal human organs and tissues. The combination of immunohistochemistry and tissue microarrays provides protein expression patterns in a large number of different tissue types. Immunohistochemistry is also used for protein profiling in the most common forms of human cancer. See also Cutaneous conditions with immunofluorescence findings Chromogenic in situ hybridization References Further reading External links The Human Protein Atlas Overview of Immunohistochemistry--describes all aspects of IHC including sample prep, staining and troubleshooting Immunofluorescent Staining of Paraffin-Embedded Tissue (IF-P) IHC Tip 1: Antigen retrieval - should I do PIER or HIER? Histochemical Staining Methods - University of Rochester Department of Pathology Immunohistochemistry Staining Protocol Histology Immunologic tests Protein methods Anatomical pathology Staining Laboratory techniques Pathology