Abstract
The classification of tumors of the bladder falls into three basic categories, histology, patterns of growth (e.g., papillary vs nonpapillary, invasive vs noninvasive), and malignancy grade. The histological tumor types primary to the urinary bladder epithelium are urothelial (transitional), squamous, glandular, and small cell. By far the most common histologic type is urothelial (transitional) (approximately 90%). The bulk of this discussion will therefore deal with this tumor type. However, as they comprise approximately 10% of primary bladder tumors a brief overview of some of the other tumor types is also indicated.