In the microscopic diagnosis of neoplasms, the application of immunologic research methods to histopathology has been resulted in marked improvement. Although histologic analysis of hematoxylin and eosin stained tissue sections remains as gold standard diagnostic method and it is at the core of the practice of head and neck surgical pathology, additionally immunohistochemistry had become a powerful tool to the pathologist. It has a significant advantage in the diagnosis of difficult tumors. The selection of antibodies for the immunohistochemical testing is made on the basis of their tumor specificity and the likelihood that they will react with the tumor under evaluation using the antibody. IHC is a well-established technique to facilitate the diagnosis of infectious and neoplastic processes in animals. Immunohistochemical studies have traditionally focused on markers of specific cell of origin and tumour type as aids in the diagnosis of specific tumours.