Kidney masses, particularly small ones, are funny things. Worrisome and usually benign, deciding what to do and when to do it is almost never clear. Active surveillance is often used to monitor. I had a small mass kidney mass show up pre chemo for breast cancer. It has been followed for 6 years with scans. About 2 years ago its appearance got “bumpy” so a little more concern. One year later scan showed no mass at all. Another scan in a year will happen.