Immunohistochemistry Staining

Immunohistochemistry (IHC) techniques can be performed in conjunction with HematoxylinHematoxylin and EosinEosin stainingStaining (H&E) and is particularly useful in certain circumstances when tumor identification can be challenging. IHC refers to the process of using an antibodyAntibody conjugated with an enzyme probe to target a specific cellular antigenAntigen. Upon binding of the antigenAntigen, the antibodyAntibody-enzyme probe complex may either produce a visible reaction product or there may be emission of light or fluorescence, allowing the positively stainingStaining cell to be readily identified on light microscopy. The high fidelity with which the antibodyAntibody probe binds its antigen and the specificity of the antigenAntigen to certain cell lineages makes IHC a valuable tool in tissue stainingStaining, allowing for better delineation of tumors from normal cells. This chapter will serve as a reference for performing IHC staining on Mohs tissue specimens. Particular attention will be paid to IHC for in situ and early invasive melanoma and squamous cell carcinoma. In addition, examples of extramammary Paget disease, basal cell carcinoma, and Merkel cell carcinoma will demonstrate the broad applicability of cytokeratin stains.