I was initially put on monitoring (posted on this recently) for an incidentally found lesion. Originally went for what turned out to be a cyst, but the ultrasound found a small, vascularized tumor (1.1cm), which turned out to be a benign Leydig Cell Tumor. However, the doc I saw first was a urologic-oncologist and I had just had a full hormone panel and blood work up that included tumor markers from a other doctor - (same system, so he had access to those results before putting me on monitoring).

If you are looking for other doctors, I found these sites to be helpful (if you are near the cities listed):

http://thetcrc.org/experts.html

https://www.testicularcancerawarenessfoundation.org/testicular-cancer-experts

I hope this helps.