Charlie
or Rocksteady
Only part of your question falls into my experience,
When they found TCC in my ureter i learned a new term pan-urothelial cancer (replacing the term bladder cancer). the idea was that the ureter, bladder and urethra share a common lining, and cancer 'migrate' up or down the system.
Cancer staying in the original system, but showing up later, could be better news than having it metastasize to the urethra. Do ask your doctor if the cancer could have been in the urethra all along, but escaped detection until now. Lets hope that the cancer has not metastasized, and that it won't be showing up anywhere else.
Check with your doc. I felt much better after learning that the existing cancer can move through, and be confined to, the urinary system.
Best
Jack