My bad, I should have mentioned the bad parts wrt the needle biopsy. But again, we don't know if they have it in mind yet and I just wanted to make you aware of the possibility.
Yes, they would have to be very careful due to the vascularity of the kidneys. But the bigger issue is cancer cell seeding due to the needle transport and the sampling itself. They usually use a cannula needle system to get to the region around the tumor. The cannula needle is larger than the actual sampling needle and remains in place after positioning. The sampling needles are then fed through the inside of it to actual get a sample from the tumor.
It's this very act that is a potential risk, although small (depends on the type of cancer, type of needle, etc). Imagine if, by taking a chunk of tissue, some very small portions (or even just a cell) happen to get loose and into the blood for transport throughout the body, well we now have a malignancy risk. Also, there maybe some cancer cells as residue left on the ends of the needles so that by simply retracting them back out of your body, you can also have needle tract seeding.
They try to minimize all this by using the cannula and by using aspirated-needles as well. But there is also going to be a risk that remains. It's a very tricky thing of balancing this risk against the knowledge that it may provide (I emphasize the "may" here, remember my case ...). Also, the bigger the diameter of the needles, the better the sample, the higher the risks ... all these things are up to your doctors and the hospital procedures wrt the risks they are willing to take on as well.
I have my own feelings on all this of course but I didn't want to scare you one way or another. Remember it's your decision to make, not your doctors, no matter how much they may want to do something. I would tell you if you want my opinion.
Yes, it is very fortuitous that they found it! And I know that feeling of "Get it out! Get it out now!!". Try and have a good weekend and good luck.