RESUMEN
It is a rare malignancy that represents less than 1% of the bladder malignant tumors. It affects children and adults with a maximal incidence beyond 60 years. The predominance of male was marked with a sex ratio 3/1. The treatment consists on a surgical exeresemonoblocsometimes preceded by chemotherapy when complete surgery is impossible. 80 years old patient with the history of lithotomy, presented a total hematuria with stones since 3 years in a context of general state deterioration. The etiologic investigation reveals a bladder mass. The complete transurethral resection was in favour of a pseudo-sarcoma. A year and a half later, the patient was admitted with a palpable pelvic mass and hematuria. Biopsy was this time in favour of a leiomyosarcoma. The scan showed a very locally advanced tumor for which the patient was treated by anterior pelvic exenteration and cutaneous ureterostomy. The anatomopathological exam confirmed the diagnosis of urinary bladder leiomyosarcoma grade1. It is a chemo-responsive tumor. Neoadjuvant chemotherapy is recommended to shrink the tumor when it is locally advanced not easily completely removed or to avoid mutilating surgery. The quality of resection is the most important prognostic factor for local recurrence. Histological grade correlates with metastatic potential. New drugs of chemotherapy such as gemcitabine have recently demonstrated efficacy inleiomyosarcoma. This is a rare entity whose treatment must be integrated into a multidisciplinary approach in an expert center. We aim, through this observation to analyze mainly the clinical, molecular and therapeutic characteristics