The contribution of immunocytochemistry in diagnostic cytology. Comparison and evaluation with immunohistology

This study reports on the use and evaluation of immunocytochemistry in diagnostic cytology by correlation with (immuno)histology. The cytologic material was collected during a period of 3 years. Sixty-four patients were selected and studied retrospectively. The reactivity of a number of polyclonal and monoclonal antibodies was investigated and applied to a diverse group of tumors. Marker expression on routine cytologic and histologic material was compared and the use of immunocytochemistry in diagnosis was evaluated. Immunocytochemistry proved to be an easy and valuable technique for the identification and classification of tumor cells, and there was a good concordance with immunohistology. A discrepancy in marker expression was found in 10% of the slides that were investigated. Immunocytochemistry led to a misdiagnosis in only four cases; however, in these cases cytology alone would not have led to the correct diagnosis. The causes for the discrepancies are discussed. It is estimated that immunocytochemistry contributed to the diagnosis of approximately 50% of the cases, supplying either additional or essential information. A wide variety of markers can be applied reliably on cytologic preparations. The use of panels of antibodies is mandatory.