RESUMEN
Carcinosarcoma of the bladder is a rare malignancy characterized by an intimate admixture of malignant epithelial elements (carcinoma) and malignant soft tissue elements (sarcoma). Patients with carcinosarcoma usually present with high-stage malignancy. Cystectomy or transurethral resection of the bladder tumor (TUR-Bt) is the preferred treatment, often followed by radiation therapy, but the prognosis is very poor1-7). To our knowledge, almost 80 cases have been reported in Japan, usually as case reports or small series6, 7). In almost all cases, the chief complaint was gross hematuria. We herein report a case of carcinosarcoma of the urinary bladder in a patient whose chief complaint was abdominal pain. His pain worsened, and the occurrence of hydronephrosis indicated that extremely rapid tumor growth may have occurred. No evidence of recurrence was noted 30 months after the performance of cystectomy.