The role of immunoperoxidase staining in diagnostic cytology.

A survey was made of the immune staining characteristics of 60 malignant neoplasms. Cytologically positive smears from each case were tested against a panel of six antibodies (alpha-antichymotrypsin, carcinoembryonic antigen, cytokeratin, desmin, vimentin and S-100 protein). The smears were decolorized and stained with polyclonal sera using the standard avidin-biotin immunoperoxidase procedure. In selected cases, the application of Diatex compound for partition of smears was necessary to obtain optimal results. Most staining reactions reflected the histogenesis of the neoplasms. However, more than one of five reactions was nonconclusive due to background staining, scanty cellularity or poor cytoplasmic preservation; furthermore, the 238 reactions scored as positive or negative included 33 unexpected positives and 15 unexpected negatives. In a series of 20 additional cases, selective immunoperoxidase staining was used in an attempt to solve specific diagnostic problems; the results in 13 of 15 cases with conclusive staining agreed with the cytologic impression. It is concluded that standard immunoperoxidase techniques can contribute to the solution of certain diagnostic problems in cytology; however, the results should be interpreted with caution and with full knowledge of the limitations of the technique.