About half the cancers in dogs are visible as growths or sores on the outer surface of the body. Signs that a tumor could be a cancer are visible growth, sores of the skin with bleeding and a wound that does not heal. A firm gray or pink open sore, especially on the feet and legs, should be attended to immediately. A hard mass that appears to be fixed on a bone is also cause for concern. Some tumors occur internally where it would be difficult to detect until they are quite large.
Sebaceous cysts are common in dogs.
They occur all over the body. Certain breeds are affected more often then others. The breeds include Kerry Blue Terriers, Schnauzers and Spaniels. It may grow to make the dog who has it itch. Eventually it is likely to become infected and will have to be drained, unless it drains on its own.