My dog has a weird lump on his chest?

My mini snausher (sp?) He's about 10 and my other dog has smaller lumps raised on hos skin that have been deemed as benign. But on this dog (the ten yr old) has lumps under his skin. The vet has been watching the other ones and says they seem harmless. But this one is like a ball. Its soft and moves, I don't think its a tumor but I'm still worried. Its about the size of a golfball and so weird!! What should I do? Could be a lymph node or cyst or is it a tumor? I dont want my dog to have a tumor! Help. Thanks.

Rule of thumb if you can get your fingers around it and it is movable, it is most likely a fatty tumour, lipoma, harmless and benign. The ones that have fingers attached and don't move are the ones to be worried about. My dog had a lot of lipomas that were benign and would get very large, sometimes when she had other operations, they would go in and remove the lipomas while she was under anesthesia. They usually only remove them when they interfere with the dogs ability to get around. You can always aspirate to check the cells.