[Retention cyst of the prostate with projection of hyperplastic tissue: report of a case].

A 46-year-old man presented at Kasukabe City Hospital because of urinary retention. Digital rectal examination revealed soft distended mass in the retrovesical space. Transrectal ultrasonography and computed tomography showed a retrovesical cystic lesion of 14 x 11 x 10 cm in size and a mass protruding into the cyst from posterior lobe of the prostate. The cyst and the mass were removed suprapubically. The cyst was filled with 400 ml of clear yellowish fluid containing acid-phosphatase and prostate-specific antigen in a high concentration, but no spermatozoa. The mass protruded posteriorily from the prostate. The wall of the cyst was partly lined with double layer of columnar epithelium. The histological examination of the mass showed marked nodular hyperplasia and dilated acini of the prostate gland was seen around the cyst. A diagnosis of retention cyst of the prostate and nodular hyperplasia of the prostate were made. Cysts of the prostate are uncommon and retention cysts protruded by markedly hyperplastic prostatic tissue are extremely rare.