Sarcomas constitute only a small proportion of the malignant growths arising in the urinary bladder. Many varieties of sarcoma are mentioned in classified lists, but some names suggest vaguely the parent tissue origin or indicate merely a poorly differentiated variety of cell components. Only a few muscle tumors are included in these lists. Munwes1 in 1910 recorded 5 myosarcomas as occurring among 94 sarcomas of the urinary bladder. Hückel's2 review, published in 1934, mentioned the occurrence of 8 leiomyosarcomas and 3 rhabdomyosarcomas among 125 sarcomas of the urinary bladder.
The details of cell structure in many descriptions of sarcoma of the urinary bladder are meager, especially in descriptions of sarcomas of muscle tissue. The latter tumors are of two types, the smooth and the striated muscle tumors. When the cells of a rhabdomyosarcoma do not become differentiated beyond the myoblastic stage, characteristics other than the cross striations are