Is a cystic lesion located at the midline of the prostate a müllerian duct cyst? Analysis of aspirated fluid and histopathological study of the cyst wall.

OBJECTIVE: In 6 patients, ranging in age from 26 to 71 years, we analyzed aspirated fluid and histologically studied cystic lesions located at the midline of the prostate. METHODS: Digital rectal examination, ultrasonography, magnetic resonance imaging, and aspiration of cystic fluid were performed to evaluate size, contents, and location of the cystic lesion. A 22-gauge needle was inserted into the cystic lesion perineally under ultrasound guidance. After extracting fluid for cytology and measurement of prostate-specific antigen (PSA) and prostatic acid phosphatase (PAP), a specimen from the prostate involving the cystic wall was collected. Hematoxylin-eosin staining and immunohistochemical staining for PSA were performed. RESULTS: All aspirated fluid specimens were yellowish and clear without any sperm or malignant cells. The PSA levels in the fluid ranged between 90 and 670 x 10(4) ng/ml, while the PAP levels were between 168 and 4,000 ng/ml. These levels of PSA and PAP were significantly higher as compared with those in the serum. The cystic wall was lined with cuboidal or columnar epithelium. Some epithelial cells from the cystic wall showed positive immunostaining for PSA. CONCLUSIONS: Not all cystic lesions located at the midline of the prostate are müllerian duct cysts, and there is a high probability that the lesion could be a cystadenoma or a simple cyst of the prostate.