Atypical hyperplasia of the prostate. A pitfall in the cytologic diagnosis of carcinoma.

The cytomorphologic features of atypical hyperplasia were studied in fine-needle aspiration biopsies of the prostate. Atypical hyperplasia material was found in 31 cases. The most usual and distinctive cytologic features of atypical hyperplasia were clustering of poorly-differentiated epithelial cells with acinic pattern and fairly regular nuclei. Another relevant feature was the lack of cytoplasmic fluorescence after acridine orange staining. These features make possible the diagnosis of atypical hyperplasia and the distinction from poorly-differentiated carcinoma. The recognition of atypical hyperplasia cells in fine-needle aspiration biopsies of the prostate is important in the avoidance of cytodiagnostic errors.