Immunohistochemical analysis of gel-transferred cells in cytologic preparations following smear division

Fine-needle aspirations on solid tumors are used increasingly as a means of obtaining a primary diagnosis. In many cases, a panel of immunostains performed on these aspirates is necessary to further characterize the cytologic interpretation. The amount of material obtained through aspiration, however, is often quite limited and is present on few glass slides. Previous studies have demonstrated the success of dividing cytologic smear preparations into smaller parts that could then be used for a panel of immunohistochemical stains. These results, however, did not compare the immunoreactivities of various antibodies before and after tissue transfer on cytologic preparations. In the present study, 41 immunohistochemical stains that employed 16 antibodies on 15 tumor preparations were performed following smear partition using the tissue-transfer technique. The percentage of cells that stained positive after transfer was determined and was correlated quantitatively to the untransferred controls. Specific immunoreactivity was demonstrated in 30 of 38 cases (79%) but was significantly decreased or lost in 8 of 38 cases (21%), which included antibodies for S-100, estrogen and progesterone receptors, chromogranin, neuron-specific enolase, and cytokeratin. Morphology was well preserved following tissue transfer, although limited cytoplasmic damage was seen in up to 25% of tumor cells. Immunopositive samples were found to be easily interpretable. Because sporadic cases fail to show immunohistochemical staining reactions following cytologic smear division and transfer, negative immunohistochemical stains in such preparations should be approached with caution.