Transitional cell carcinoma is a type of cancer that originates in the kidney, bladder, or ureter (the tube that carries urine from the kidney to the bladder).
A transitional cell is intermediate between the flat squamous cell and the tall columnar cell. It is restricted to the epithelium (cellular lining) of the urinary bladder, ureters (tubes that carry urine from the kidneys to the bladder), and the pelvis of the kidney (that portion of the kidney collecting the urine as it leaves the kidneys and enters the ureters). Transitional cell carcinomas have a wide range in their gross appearance depending on their locations. Some of these carcinomas are flat in appearance, some are papillary (small elevation), and others are in the shape of a node. Under the microscope, however, most of these carcinomas have a papillary-like look. There are three generally recognized grades of transitional cell carcinoma. The grade of the carcinoma is determined by particular characteristics found in the cells of the tumor. Transitional cell carcinoma typically affects the mucosa (the moist tissue layer that lines hollow organs or the cavity of the body) in the areas where it originates.
The most common site of transitional cell carcinoma is in the urinary bladder. Transitional cell carcinoma is the form of cancer in about 90% of cancers found in the bladder. The highest grade of transitional cell carcinoma is very likely to spread to other parts of the body. There are two primary ways that transitional cell carcinoma spreads into the surrounding structures. The first is by way of epithelial cells that line the body cavity and many of the passageways that exit the body. The other means of spread is through the lymphatic (network that resembles the circulatory system but transports proteins, salts, water, and other substances) system.
Mark Mitchell M.D., The Gale Group Inc., Gale, Detroit,