Dori, most of what I have read strongly suggests that transitional cell carcinoma in the urinary tract is possibly entirely environmental and in canines it’s suggested that’s it’s suspected causal agents may be certain flea control products and cyclophosphamide. Cyclophosphamide is ironically used as a chemotheraphy and autoimuune disorder agent. There are other predisposing factors such as repeated urinary infections, dogs required to hold their urine for lengthy periods, etc.
Causes
Flea-control products (organophosphates and carbamate) and cyclophosphamide.
http://www.petmd.com/dog/conditions/cancer/c_dg_urinary_carcinoma
