Giant Müllerian duct cyst mimicking prostatic malignancy.

A giant müllerian duct cyst was initially interpreted as a seminal vesicle cyst. Associated prostatic malignancy was suspected because of raised tumour marker levels and lysis of pubic bone. Intraoperative vasography gave the correct diagnosis. Open partial transvesical excision of the cyst and suprapubic prostatectomy were performed. No malignancy was found in the surgical specimens and 2 years later the patient remains well.