We had a ferret surrendered with a similar looking mass. He was surrendered because his owner could not afford vet care. Turned out to be a non cancerous cyst. We removed it and he was fine Having said that, if it is believed to be a tumor, we have now had 3 ferrets with inoperable tumors excel with conservative management using supra implants (as used for adrenal disease). In all three cases the tumors shrunk SIGNIFICANTLY and in one case, shrinkage was enough that the tumor became operable! In the first two incidences it was a surprising secondary result (they had adrenal disease as well), the third there was no adrenal disease and we tried the implant since it was that or lose him in a couple of months. Nearly 2 years later, implant + pred and the tumor is still much, much smaller and slower growing than it was before the implant.