A sebaceous gland tumor is an overfilled sebaceous gland, which we especially encounter in older dogs. They are usually in the neck or on the back. It is larger or smaller bumps in the skin that often have a crust. Often it is possible to squeeze out the sebum, but this is not necessary with a quiet-looking lump, which doesn’t bother the dog. In general, the bumps are benign. They can only sometimes give rise to an inflammatory reaction, which makes it necessary to remove the lump. Very rarely, a sebaceous gland tumor can degenerate malignantly. This is called a sebaceous gland adenocarcinoma.