Tumors of the bladder comprise but a small percentage of all the tumors of the body, this being variously estimated at from 0.75 per cent, to as high as 5 per cent, of the total number. Of these, approximately one half are malignant, and most of the remainder potentially so, in that they later become malignant. TYPES OF BLADDER TUMORS There are two common varieties of bladder tumors: papilloma and carcinoma. The papillomas are fibrous, benign or malignant, and the carcinomas adenoid or diffuse, adenomas being very rare. Besides these common varieties of epithelial origin, other types of tumor are found occasionally, including myomas, angiomas, fibromas and various types of sarcomas. The papillomatous growths, benign or malignant, are by far the commonest form of tumor found in the bladder. Ewing1states that this is due to the structure of the mucous membrane and the physical conditions to which the