He is not going to get a diagnosis online. He can either trust his vet, wait and see, go along with recommendations.
The other option would be to move forward and have diagnostic testing done to get an exact diagnosis. It will cost about $1000. based on my experience. The results will confirm that the condition is benign, or that the tumor is malignant, depending on whether or not the tumor has spread, treatment options (if any) will be identified.
PS: No, If you try to stay logged in, it will time out.
