Hab123,
Any time you (your father) have any concern about the care you are receiving, it is reasonable to seek an additional opinion or change to a care providers who's services are a better fit for your immediate needs.
I am responding because of your statement of only one kidney, and now cancer may be in that kidney. That is my situation at year 5 of bladder cancer. My other kidney was lost many years ago to trauma.
I don't know your hospital first hand, but you are likely to benefit having moved from a urology practice to a cancer center. You are likely to have a team available to focus on preserving the kidney - which ever type of cancer they may find - as well as planning for a possible kidney transplant and other options.
Thank you for advocating for your father. That is perhaps the most important need when dealing with cancr,.
Best,
Jack