A case of prostate stromal sarcoma involving the rectum.

Sarcomas and related proliferative lesions of the specialized stroma of the prostate are very rare and have been classified into prostate stromal sarcoma (PSS) and prostatic stromal tumor of uncertain malignant potential based on histology. We herein describe a case of PSS. A 40-year-old male presented at a hospital with urinary distention. Magnetic resonance imaging revealed a large prostate mass, and the diagnosis was prostate sarcoma of uncertain differentiation by ultrasound-guided needle biopsy. Total pelvic exenteration was performed and a pathological diagnosis of PSS was ultimately reached. Ten months later, there have been no signs of metastasis or recurrence.