Upon surgical exploration, a sizeable globular mass directly attached to the prostate base was found. The mass displaced the bladder anteriorly and both seminal vesicles were unrecognizable. No connection to the proximal urethra was identified; the rectum and bladder did not appear to be involved. Gross examination revealed a 9 × 7-cm, firm, rubbery, tannish-gray mass with clearly delineated yet tightly adjoined solid and cystic components attached to fibrous tissue (Fig. 1B). An adjoining multilocular cystic mass ruptured during surgery. Microscopically, the mass appeared to originate from the CZ, in close proximity to the vas deferens and seminal vesicles. Due to distension and stretching, parts of the large cyst remained as flat mono-layered epithelial cells and had paper-thin fibrous walls. The tandem arrayed prominent intraluminal ridges and extensive arborizing complex glands were noteworthy (Fig. 2A). The hallmark lobular pattern or eccentrically curvilinear branched hyperplastic glands, usually seen in conventional nodular hyperplasia, were not identified. Urothelium, representing either TZ or prostate urethra, was not found. Focal areas of the solid mass had leaflets with profound stromal cells projecting into the cystic cavity, which mimicked phyllodes tumor (Fig. 2B). Intraluminal snouting and tufts were occasionally seen, however, cellular atypia typically found in prostatic intraepithelial neoplasia (PIN) was not present. There was no cytological atypia or appreciable mitosis. Epithelial cells were strongly immunoactive to PSA. Seminal vesicles showed marked luminal obliteration by fibromuscular hypertrophy and periluminal amyloidosis (Fig. 2C), which was not previously noticeable on radiological images and gross examination.

In our case, the patient's main symptom was aspermia, likely caused by a compressed seminal vesicle. The seminal vesicle is composed of 2 distinct muscle propers: a thin external longitudinal and a thicker internal circular muscle layer.⁹ In our case, portions of the vas deferens and seminal vesicles showed nearly complete fibrous obliteration and a relatively thick external muscle proper.

This pelvic mass apparently originated from the prostate, due to the intense immunoreactivity to PSA. The elevated PSA in the present case suggests microvasculature influx, such as rupture from the markedly dilated cystic glands. In a few documented cases,^1,2,4,5 PSA level was not proportionally related (CC = 0.25) to mass volume (Table 1). Therefore, further studies regarding the interrelationship between tumor volume and PSA level are required.