Metastatic ductal adenocarcinoma of the prostate: cytologic features and clinical findings.

We retrospectively reviewed the cytologic features of metastatic prostatic ductal carcinoma (PDC) in 23 cases, clinical manifestations, and clinical outcomes. Cytologic smears typically showed tumor cells with abundant cytoplasm and oval nuclei arranged in papillary groups or flat and folded sheets, some of which showed peripheral nuclear palisading. However, these features could be focal, subtle, and even indistinguishable from those of acinar carcinoma, particularly when the ductal component was predominantly of a cribriform and solid pattern or coexisted with acinar carcinoma. A determination of a prostatic origin of a metastatic PDC, based on cytomorphologic features alone, could be difficult. Immunostaining for prostate-specific antigen and prostatic acid phosphatase proved helpful in determining a definitive diagnosis. The median followup of patients was 82 months, the median overall survival was 77 months, and the 5-year overall survival rate was 72%. Tumor growth pattern did not correlate with prognosis, but visceral metastasis conveyed a poor prognosis. The correlation with clinical and radiologic findings, a high index of suspicion, and the use of immunoperoxidase studies are important in making an accurate diagnosis.