Common Tumors in Dogs

Tumors in dogs can be either benign or malignant, and certain types of tumors are more common than others. Cancerous tumors generally fall into one of two categories: carcinomas or sarcomas. The difference between these two is infinitely important when trying to understand different types cancer that effect dogs. Carcinomas are typically comprised of the cells covering the surfaces of the body, such as the skin or blood vessels.

Sarcomas, on the other hand, develop from connective tissues, like the bone, muscle, and cartilage. And then there are benign tumors, which essentially do not spread and have no detrimental effect on a dog. Learning about these differences of tumors is an important part of understanding and dealing with some of the most common types of tumors in dogs.


Osteosarcoma tumors are cancerous and manifest within the bones of a dog, causing tremendous pain, difficulties walking and a reduced tolerance for exercise. Because they affect the bones and their function, they are appropriately labeled as sarcoma-type tumors. Furthermore, they seem to appear most commonly in larger breed dogs, including Saint Bernards, Dobermans and Great Danes.

Osteosarcoma is extremely aggressive in that it spreads and develops quickly, most of the time progressing as far as the lungs and, at that point, only allowing for a 50% chance of survival. Because of its advanced nature, early detection is the key to a dog’s survival of osteosarcoma. If the tumor can be detected early enough, treatment can be successfully rendered, but there will be a high probability of limp amputation.


Lipoma is a benign tumor that typically does not cause any serious problems. It is a fatty tumor that can be found beneath the outer most layer of skin, although it can sometimes become attached to both the muscle and connective structures. Lipomas are often detected as simply a lump on a dog’s body that feels jelly-like in consistency. In most cases, there is no need for removal or even treatment of lipomatous tumors. Because they are noncancerous and do not usually interfere with everyday living, most veterinarians disregard them altogether. If they begin to affect a dog’s normal functions or level of comfort, however, there are treatment options that can be successfully used.

Mast Cell Tumors

Mast cells are a major part of the immune system in dogs because they release chemicals into the bloodstream when a foreign invader, such as a parasite, is identified. These chemicals are toxic enough to kill off bacteria and parasites; thus mast cells play a major role in the effective function of the immune system. In essence, a mast cell tumor consists of several mast cells, employing the opposite intended function of the immune system.

The cause of mast cell tumors is still undeterminable, but it is thought that a hereditary link may be the largest contributor for these types of tumors. Because of the chemicals that are contained in mast cell tumors, removing them can sometimes trigger an immediate release of the chemicals contained in mast cells into the bloodstream, creating havoc and influencing blood pressure. This type of tumor remains to be one of the more common and dangerous types of tumors in dogs.