Fine needle aspiration cytology of a metastatic duct carcinoma of the prostate: a case report

BACKGROUND: Prostatic ductal carcinoma (PDC) is a rare variant of prostatic adenocarcinoma. Without proper clinical information, a fine needle aspiration (FNA) diagnosis of metastatic PDC can be challenging as this tumor can morphologically mimic adenocarcinomas from other sites. To our knowledge, FNA findings of metastatic PDC have not been previously reported. CASE: An 85-year-old man presented with a large, destructive pelvic bone lesion with soft tissue extension. He had undergone a prostatectomy 30 years earlier for "benign prostatic hypertrophy" but had no known history of malignancy. The aspirates were hypercellular and composed of numerous monolayered or folded cohesive sheets of tumor cells with minimal cytologic atypia. The tumor cells had abundant, clear cytoplasm, evenly spaced nuclei, finely granular chromatin, inconspicuous nucleoli and occasional mitotic figures. The background was clean and contained a few wisps of thin mucin. Cell block sections revealed tumor cells forming tubulopapillary architecture lined with tall columnar cells with focal nuclear pseudostratification, reminiscent of uterine endometrial carcinoma. Positive immunoreactivity for prostate-specific antigen and prostatic acid phosphatase confirmed the tumor's prostatic origin. CONCLUSION: Because of the rarity and nonspecific cytomorphologic characteristics of this tumor, clinical history, radiologic findings and a high index of suspicion in conjunction with ancillary studies are important in achieving a correct FNA diagnosis of metastatic PDC.