Spectrum of Cystic Epithelial Tumors of the Prostate: Most Cystadenocarcinomas Are Ductal Type With Intracystic Papillary Pattern

Cystic epithelial tumors arising from the prostate are rare, and their full histologic spectrum has yet to be defined. Herein, we present 8 examples of prostatic cystic tumors including 1 giant multilocular cystadenoma and 7 cystadenocarcinomas. We divided the cystadenocarcinomas into “giant multilocular” cystadenocarcinoma (3) and “microscopic” cystadenocarcinoma (4) because of their differing clinical presentations with clinically apparent cystic masses in the former. The cystadenoma was an 11 cm multilocular cystic pelvic tumor in a 55-year-old man who presented with lower urinary tract symptoms. The cystadenoma was lined predominantly by benign acinar cells and had a distinct basal cell layer. No recurrence occurred 3 months after resection. The 3 patients with giant multilocular cystadenocarcinomas were 62 to 82 years old, had large pelvic cystic masses (up to 16 cm), and 2 presented with obstructive urinary and lower intestinal tract symptoms. One giant multilocular cystadenocarcinoma had a markedly high cystic fluid prostate-specific antigen at >80,000 ng/mL. All 3 giant multilocular cystadenocarcinomas were ductal adenocarcinoma with exuberant intracystic papillary formations. One tumor was associated with a high-grade noncystic conventional (acinar) adenocarcinoma (Gleason score 9 [ISUP grade group 5]). Follow-up on the 3 giant multilocular cystadenocarcinoma cases (7 to 21 mo) showed multiple metastases in 1 patient but was attributed to the high-grade conventional adenocarcinoma component. In addition, we described 4 examples of microscopic cystadenocarcinomas that were small (⩽1 cm) solitary or multiple cystic tumors identified on pathologic examination of the prostate. In 3 of 4 microscopic cystadenocarcinomas the lining was ductal adenocarcinoma with occasional to exuberant papillae and appeared similar to the smaller cysts in the giant multilocular cystadenocarcinomas. One of the 4 microscopic cystadenocarcinomas had an acinar adenocarcinoma lining with occasional papillae and was associated with a conventional adenocarcinoma. Follow-up of the 4 patients with microscopic cystadenocarcinoma (1 to 14 mo) showed no evidence of disease. Review of literature highlighted similarities between the findings in our cases and previously published prostatic cystadenocarcinomas, including the markedly high cystic fluid prostate-specific antigen level in giant multilocular cystadenocarcinomas and the typical ductal adenocarcinoma morphology with intracystic papillary pattern. In conclusion, cystic epithelial tumors of the prostate exhibit unique clinicopathologic features. Cystadenocarcinomas, whether the clinically apparent giant multilocular form or the incidentally identified microscopic type, represent a rare underrecognized pattern of prostatic adenocarcinoma mostly within the histologic spectrum of the ductal variant.