Several benign and malignant nonepithelial and stromal-like lesions arise in the prostate. Because such lesions are rare, their recognition is essential, because treatment and prognosis depend on an adequate pathohistologic classification. We report a case of an 83-year-old man with a stromal tumor of the prostate of uncertain malignant potential (STUMP). He presented with urinary retention and rectal constipation. On bimanual examination, a rectally and suprapubically palpable mass was found. Imaging studies revealed a 12 x 8 cm pararectal inhomogeneous mass of uncertain origin compressing rectum and urethra. The tumor was resected by a retropubic approach and examined immunohistochemically.