Keratin immunoreactivity in fine‐needle aspiration of the prostate: An aid in the differentiation of benign epithelium from well‐differentiated adenocarcinoma

The efficacy of utilizing immunocytochemical staining of prostatic basal cells in separating benign from malignant prostatic epithelium was tested by staining fine‐needle aspiration smears of prostatic lesions with the monoclonal antibody EAB‐903. This antibody has been shown to stain keratin subtypes present in the prostate only in basal cells. The study utilized 12 benign, nine malignant, and four suspicious‐for‐carcinoma cases. Ten of 12 benign cases showed an intermingled pattern of staining, which was not found in the malignant cases. Our findings indicate that this distinctive pattern of staining may assist in distinguishing benign epithelium from well‐differentiated prostatic adenocarcinoma.