[Giant phyllodes tumor of the prostate].

A 55 year-old man complained dysuria and visited to our hospital. Physical examination showed firm large mass occupying whole abdomen. Computed tomography (CT) demonstrated a huge retroperitoneal tumor which compressed intestine, liver, kidney, and urinary bladder. We performed extirpation of the tumor (8.6 kg, largest diameter 60 cm) which was composed of myxoid stromal region associated with cystic pattern. Histological examination revealed that the epithelium of the cystic region was positive for prostate specific antigen (PSA) immunostaining. The tumor was diagnosed phyllodes tumor of the prostate (prostatic stromal proliferation of uncertain malignancy, PSTUMP). Serum PSA was declined 3.9 ng/ml to 0.9 ng/ml; however, magnetic resonance imaging (MRI) demonstrated a residual (recurrent?) tumor in the pelvis one month after the operation. We carried out total prostatectomy and residual tumor resection. Phyllodes tumor of the prostate is histologically characterized with biphasic pattern of hyperplastic epithelial cysts and variably cellular spindle stroma. The tumor is considered to have malignant potential and several histological factors including cellularity, atypia, etc. are utilized to assess it. However diagnostic criteria and subsequent treatment modalities are not established thus far. Previous reports showed efficacy of total surgical removal rather than partial resection and that we performed radical extirpation of the entire tumor. Close follow up is needed against this frequently recurrent disease.