Methodological aspects and application of the immunoperoxidase staining technique in diagnostic fine-needle aspiration cytology.

The immunoperoxidase method was modified and adapted for use on cells obtained by fine-needle aspiration biopsy for routine diagnostic cytology. Combinations of different modes of fixation and graded trypsinization were tested. Best results were obtained with fixation in formol-acetone followed by enzyme digestion for 3-6 min; exact times were adjusted for the individual antigen. With optimal conditions as to fixation and proteolytic digestion, the method was found to be sensitive and reproducible and without artifactual background staining. Various intracytoplasmic antigens of diagnostic importance such as immunoglobulins, prostate-specific antigen, keratin, thyroglobulin, S-100, alpha-1-antitrypsin, and lysozyme in lymphoid cells, bone marrow cells, and tumor cells of epithelial and mesenchymal origin were detected. Staining of newly prepared or up to 2-yr-old specimens gave equally good results. Both cellular morphology and the results of immunoperoxidase staining can be studied simultaneously. The method is considered valuable for increasing accuracy of diagnostic cytology.