Immunocytochemistry in head and neck aspirates. Diagnostic application on direct smears in 16 problematic cases.

This report describes our experience with immunocytochemical staining of routinely processed smears in the fine needle aspiration (FNA) biopsy diagnosis of 16 tumors of the head and neck. Immunocytochemistry (ICC) was performed on alcohol-fixed or air-dried smears using commercially available monoclonal antibodies followed by a streptavidin-biotinylated peroxidase labeling method. In 12 aspirates with cytologically unclassifiable and undifferentiated cells, immunostaining for cytokeratin, leukocyte common antigen, S-100 protein and vimentin provided conclusive evidence of cell lineage. ICC permitted the correct identification and differential diagnosis of four additional tumors: a positive immunoreaction for thyroglobulin identified a metastatic Hürthle cell carcinoma of the thyroid; a coexpression of two distinct classes of intermediate filaments helped support the FNA diagnoses of a parathyroid adenoma and of a synovial sarcoma; and the double immunoreaction for CD15 and CD30 antigens helped identify Reed-Sternberg cells within an unusually suppurative harvest. Two immunostains were required for proper diagnosis in 13 cases and four in the remaining 3. In all cases but one only unstained slides were used. These data demonstrate that immunostaining can conveniently and advantageously be performed on direct smears of aspirated samples of head and neck lesions, but cases should be carefully selected for this procedure.