Good morning, Mike... I knew you wouldn't be resting on your laurels but trying to think of anyone you can help. Organ donation is a wonderful gift but does not come without its risks as you undoubtedly have found some references to that effect.
Your question reminded me of a story I read a couple of years ago so I searched it out again. A man was given a kidney transplant, but within months had contracted uterine cancer that had metastasized from the woman's kidney. She did not know she had cancer at the time of her death. The link below covers that story, but also ABC news dug a bit deeper into the issue and talks about transplant and possible disease transmission risks. It will be interesting to see what your doctors have to say about the possibilities you raise as well.
Cancer From Kidney Transplant