Application of immunohistochemistry to cytology

Context. - The uses of monoclonal antibodies via immunochemistry have been reported frequently within the literature using various methodologies with applications to cytology specimens. The direct application of immunocnemistry to cytology may have a variety of pitfalls that the general pathologist familiar with its application to histology may be unaware of when applying it prospectively to patient specimens. Objective. - To review common pitfalls when applying immunochemistry to cytology specimens and to suggest approaches to the more common differential dilemmas that apply to a variety of cytology specimens that could be seen in a general pathology practice. Data Sources. - The authors' own experiences of applying immunochemistry to cytopathology specimens within an academic setting along with supportive data from the literature. Conclusions. - Immunochemistry can be used to increase the predictability of a cytology diagnosis if care is taken with the cytology sample preparation methodology and there is judicious use of select monoclonal antibody panels to support a specific cytology diagnosis. Up-to-date evidence-based antibody databases should be used when selecting antibody panels.