@gobib Welcome to Mayo Clinic Connect. I can only imagine how nerve-wracking this must be for you!

Your best move is to frankly ask your medical team why the two month recheck, what differences would they see to go ahead and do something. Don't wait until the two months go by to ask!

I had a growth/possible tumor show up unannounced in a scan April 2020, on my right kidney. The location was awkward, in the upper poles. I went with scan every 6 months [smaller size than yours] for a couple of reasons. The doctor felt that due to my kidney disease stage of 4 at that time, plus my active blood cancer involving chemo, he did not want to put me under additional risk with surgery. Since them, it has been determined that rather than a tumor, it is a complicated cyst.

While this discussion about Complex Cysts shows in both the the "transplant" and "kidney and bladder" groups. there is a lot of good information here:
https://connect.mayoclinic.org/discussion/renal-complex-cyst/
Do you think your doctors may determine the same as mine?
Ginger