I am really scared. I was petting Monster and I felt a lump on his back near his left shoulder blade. I plan on taking him to the vet, but does anyone know what may cause a lump? Its small and I can't tell if its fluid inside or if its tissue. He is 7 months old, neutered, has always been healthy to my knowledge. There hasn't been any changes in his behavior or eating habits. He has never vomited at all and his litterbox habits are normal as well. I know I have to take him to the vet and I am going to believe me I'm so worried, but can anybody give me any ideas on possibilities?