Answer: Prostatic urethral polyp

Histology: This lesion both has a polypoid and a papillary architecture. The papillary fronds are lined variably by thin benign urothelium and by cytologically bland columnar epithelium. The stalks of the papillary fronds have a fibrous appearance. Within the polypoid base of the lesion are histologically benign prostatic glands.

Discussion: Ductal adenocarcinomas may present in a similar fashion with a polypoid mass projecting into the prostatic urethra. The most common patterns of ductal adenocarcinoma are papillary and cribriform. Papillary prostatic duct adenocarcinomas consist of papillary fronds lined by pseudostratified columnar epithelium with a range of cytologic atypia from fairly bland to pleomorphic. One does not see benign prostatic glands within prostatic duct adenocarcinoma nor does one see papillary fronds lined by urothelium. Villous adenomas occur in the bladder and have the exact morphology as seen with villous adenomas occurring in the gastrointestinal tract. They are also lined by pseudostratified columnar mucinous epithelium. Villous adenomas are not typically found within the prostatic urethra. Benign urothelial papillomas consist of fibrovascular cores lined by entirely normal urothelium. In contrast to prostatic urethral polyps, the stalks within prostatic urethral papillomas tend to have a delicate appearance consisting of loose connective tissue rather than the dense fibrous and muscular tissue characteristic of prostatic stroma seen in the current case. One would not expect to see within an urothelial papilloma benign prostatic glands within the polypoid base of the lesion. Prostatic urethral polyps are entirely benign and occur over a wide age range from adolescence to the elderly. Similar lesions may be seen outside the prostatic urethra, most commonly in the bladder, where they are termed ectopic prostatic polyps.