An adult atypical fibromyxoid tumor of the urinary bladder.

A case of atypical fibromyxoid tumor of the urinary bladder in a 32-year-old woman is reported. The patient had never complained of urinary symptoms, and bladder tumefaction was revealed fortuitously at pelvic ultrasound. Cystoscopy revealed a peanut-sized mass. Microscopically, the lesion was composed of strap- and tadpole-shaped cells resembling rhabdomyoblasts. For this reason, the tumor was initially diagnosed as embryonal rhabdomyosarcoma. However, immuno-histochemical study was negative for muscle origin, and the tumor has subsequently proved benign. The reported case illustrates the value of immuno-histochemical study in the evaluation of the true type of bizarre stroma cells in this pseudo-sarcomatous lesion. Their recognition is important, because the therapeutic consequences of misinterpreting this tumor as a sarcoma are great.