Urine cytology has been effectively used in the diagnosis and management of epithelial bladder tumors, particularly high-grade urothelial carcinoma. Indeed it is the gold standard for bladder cancer screening. Although urothelial carcinoma is the most frequently identified bladder tumor by urine cytology, metastatic carcinomas from the kidney, colon, and a variety of other regional organs have been detected. Stromal lesions such as inflammatory myofibroblastic tumor, gastrointestinal stromal tumor, and leiomyosarcoma are other much rarer entities occurring within the bladder. Few to no case reports exist documenting their identification within urine cytology specimens. Herein we report the detection of a high-grade prostatic sarcoma within a catheterized urine specimen of a young male having a diffusely enlarged prostate. The specimen consisted of numerous fragments of relatively uniform spindle cells having ovoid nuclei with rounded ends and finely dispersed chromatin. Cytoplasmic borders were indistinct. No mitoses or significant atypia was present. The background consisted of numerous red blood cells, cellular debris, and a few clusters of unremarkable urothelial cells. Followup surgical biopsy of the patient's prostate revealed a high-grade spindle-cell sarcoma. Further immunohistochemical and molecular delineation of the tumor was not informative for a more definitive diagnosis. Although rare, sarcomas and other mesenchymal tumors involving the bladder are unique entities with a broad differential diagnosis.