IMMUNOCYTOCHEMISTRY IN THE ASSESSMENT OF PS2 PROTEIN EXPRESSION IN FINE-NEEDLE ASPIRATION CYTOLOGY FROM BREAST-CARCINOMA

pS2 protein is a cysteine-rich polypeptide, of unknown function, the e xpression of which is induced in the human cancer cell line MCF-7 by o estrogen. The availability of a murine monoclonal antibody to human pS 2 protein has prompted us to evaluate its expression in 47 cases of pr imary breast carcinoma; Using a double indirect immunoperoxidase techn ique, we compared the expression of pS2 protein in fine needle -aspira tion (FNA) cytology smears with that in formalin-fixed, paraffin-embed ded sections from subsequently excised tumours from the same patients. We also. compared the expression of pS2 protein and oestrogen recepto r (ER) status using immunocytochemical assay (ER-ICA) in formalin-fixe d, paraffin-embedded sections from 22 primary breast carcinomas. We fo und the application of immunocytochemistry in the assessment of pS2 pr otein expression in FNA cytology to be a reliable and cost-effective t echnique, having a sensitivity of 84% and a specificity of 100%. There was also a good correlation between the expression of pS2 protein and ER status.