Health and Nutrition

Cancer in Dogs



A form of cancer that originates in the endothelium, which is the lining of blood vessels and spleen. These tumors are highly malignant and can be found almost anywhere in the body. The spleen, pericardium and heart are prone to be affected.

These tumors are most common in medium-sized or large breeds of middle aged or older dogs but can occur in any breed, including cross-breeds. German shepherds are reported to be more susceptible to this form of cancer than most dog breeds. The Golden Retriever also seems to have a higher than normal incidence.

Quite often there is little warning of the presence of these tumors before severe clinical signs are seen. An estimate of the average time from discovery of the tumor until death occurs in affected dogs is six to eight weeks.

The most common initial symptoms include visible bleeding, usually in the form of nosebleeds, and signs associated with blood loss, such as weakness, tiring easily, paleness to the mucous membranes of the mouth and eyes, increased respiratory rates, and abdominal swelling. In some cases, dogs just suddenly die with no clinical signs observed at all.

If a tumor in the spleen is found when it is small, it may be possible to remove the spleen or remove tumors found near the heart in order to prolong the dog’s life. However, most often these tumors have spread by the time they are identified. According to published papers, the average survival time in dogs with Hemangiosarcoma is only three to four months.



While Histiocytosis is quite rare in other breeds, it is inherited in the Bernese Mountain Dog and the most common type of cancer found in this breed.

There are two types of Histiocytosis: malignant and systematic. Early symptoms include depression, lethargy, loss of appetite and weight loss. In systematic Histiocytosis skin abnormalities are common on the face and limbs. If the tumor has spread to the lungs, there may be trouble breathing as well and anemia is also common. Malignant Histiocytosis progresses rapidly and has usually metastasized by the time it is diagnosed.

The mode of inheritance of Histiocytosis in the Bernese Mountain Dog is polygenic, meaning many genes are involved. Because it generally does not develop until the dog is middle-aged or older, it can be hard to identify parents that carry the trait. Conscientious efforts by all breeders and owners are needed to help eliminate it from the gene pool. Owners should report all cases to their breeder.

Additional Information:


Osteosarcoma is the most common bone tumor found in dogs, usually striking the leg bones of larger breeds. Usually seen in middle aged or elderly dogs, however, Osteosarcoma can arise in a dog of any age with larger breeds tending to develop tumors at younger ages.

Although Osteosarcoma can develop in any bone, the limbs account for 75-85% of affected bones. Developing deep within the bone and becoming progressively more painful as it grows outward and the bone is destroyed from the inside out. Over a period of one to three months, intermittent lameness can become constant. Obvious swelling is also seen as the tumor grows and normal bone is replaced by tumorous bone.

Additional Information:

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Books & Other References

Pointing the Bone at Cancer: In Dogs, Cats & Humans

Heal: The Vital Role Of Dogs In The Search for Cancer Cures

Note: This section of the Canada’s Guide to Dogs website is intended as a source of information only. It is not intended as a substitute for professional care. Always consult with your Veterinarian about health related matters.

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