Sarcomas occur infrequently. Carcinomas often invade into the bladder wall and are most often located in the trigone where they may occlude the urethra or ureters. They frequently metastasize to lung and reginal lymph nodes and may metastasize to liver, eyes and bone. Bladder tumors of any histologic types occur infrequently in cats. Transitional cell carcinoma is the histologic type that occurs most often in cats.
Bladder tumors occur more frequently in female dogs and male cats.
One known predisposing cause of transitional cell carcinoma is the previous administration of cyclophosphamide, a chemotherapeutic agent also used in treatment of some immune mediated disorders. In one report of dogs which developed cyclophosphamide-induced transitional cell carcinoma the duration of therapy ranged from 6 to 64 weeks. Urinary tract infection is often associated with a bladder tumor so treatment for UTI may temporarily improve the signs of a patient with a bladder tumor. Because of the similarity of signs and improvement following treatment with antibiotics, a diagnosis of neoplasia is often delayed. Physical examination is usually normal but a caudel abdominal mass is occasionally palpated.