An atypical fibromyxoid tumor of the prostate.

An unusual fibromyxoid tumor of the prostate is described that may be confused with embryonal rhabdomyosarcoma (botryoid sarcoma). The cells were fibroblastic, and the tumor lacked mitotic activity. Rhabdomyoblasts were not seen under either light or electron microscopy. Although the cells presented a strap-like appearance, striations were not observed. Results of immunoperoxidase studies were also negative for muscle origin. The tumor has pursued a benign clinical course.