[Anonymous]

If it is an abscess, blocked anal glands. I would get it taken care of right away.
If it is some type of tumor and it is causing him discomfort? Ask the vet that examined him for more information.

I understand your concerns, in order to treat the dog, the veterinarian has to diagnose the condition first, in order to diagnose they usually have to do lab work, ultrasounds or x-rays…..

But, if it was my dog I would see the vet again, or get another opinion. See what he advises and go from there.