Transitional cell tumors comprise 95% of bladder tumors.

Transitional tumors include the exophytic papilloma, inverted papilloma and transitional cell carcinoma.

Exophytic papilloma:

Exopytic papilloma is a rare tumor. Microscopically, the tumor is composed of papillary structures which are covered by normal appearing urothelium of seven or less epithelial layers. These tumors may recur.

Inverted papilloma:

Grossly, inverted papilloma appears as a smooth surfaced nodule. Microscopically, the tumor is comprised of papillary structures with inward growth within the bladder wall.

Transitional cell carcinoma:

From bladder tumors, nearly 95% are transitional cell carcinomas, about 5% are squamous cell carcinomas and adenocarcinomas are rare.

These tumors are more common between the ages of 50-80.

The predisposing factors include, chemical carcinogens such as arylamides, therapy with cyclophosphamide, cigarette smoking, infection with Schistosoma haematobium, and chronic use of analgesics.

Clinically, the tumor may present with painless hematuria, frequency, or dysuria.

Grossly, these tumors appear as flat to sessile to pedunculated nodules.

Microscopically, these tumors are made of papillary structures which are lined by an epithelium that resembles the urothelium. Depending on the degree of differentiation, papillary structures are well formed (grade I). Those that are made of sheets to single cells that invade the wall of the urinary bladder are poorly differentiated (grade III). Carcinoma in situ of the bladder appears as a flat lesion and show dysplastic changes throughout the thickness of the urothelium without evidence of invasion of the underlying lamina propria.

Transitional cell carcinomas may show evidence of squamous or adenocarcinomatous differentiation.

The tumors well differentiated tumors tend to recur, and the poorly differentiated tumors invade locally and may metastasize.

The most common tumor associated with Schistosoma haematobium is squamous cell carcinoma.