Sassy had one of both sides of her neck. I was told by the vet I was taking her to, there is a way to figure out if the lumps are cancerous or not. If you can grab the lump and move it around, it isn't cancerous. He said the cancerous lumps literally have 'roots' and will not move. If you try to move them, it will take some strength and will cause the dog discomfort. I'm not sure if this is 100% correct, but I trusted my vet, and they never bothered her, so I left them alone. My mother's pitbull ended up dying of a large cancerous mass they operated once, and it came back, but worse), and after seeing her lump vs. my beagles lumps, there is a difference, so he might be right.