Introduction
Cancer is one of the leading causes of death in domestic dogs - especially older dogs - which is partially due to the fact that companion animals are living longer with continual improvements in nutrition and veterinary care. How cancer affects a particular dog depends upon the type of cancer and the biological make-up of the individual animal. Meaningful generalizations about the effects of cancer cannot be made. Ultimately, however, most untreated or untreatable malignancies will cause or hasten death.
Symptoms of Cancer
One of the most common signs of cancer in dogs is the appearance of a lump or mass. Usually, the dog does not seem to notice or be bothered by the lump. However, while it may or may not be malignant, any mass is abnormal and should be evaluated by a veterinarian. Other signs of cancer are nonspecific and largely depend upon the site of origin of the primary tumor, the presence of any metastatic lesions in areas other than the site of origin, and whether there has been any rupture or other acute consequence from the disease. Depending on where the cancer is present, the signs can include:
- Superficial or subcutaneous skin masses
- Weakness
- Lethargy
- Fatigue
- Lack of appetite (anorexia; inappetance)
- Vomiting
- Enlarged lymph nodes
- Diarrhea
- Weight loss
- Pale mucous membranes
- Lameness, swelling around leg joints, pain (osteosarcoma)
- Fever
- Collapse
- Spontaneous bleeding (hemangiosarcoma)
A common consequence of cancer is something called “cancer cachexia,” which refers to the severe involuntary weight loss, fatigue, anemia and wasting of body tissues associated with underlying neoplastic disease.
Dogs at Increased Risk
No particular breed, gender or age of dog is especially prone to developing cancer. Of course, older animals tend to develop diseases, including cancer, more often than very young animals, but making generalizations about predispositions to cancer are not particularly helpful. One generalization that does seem accurate is that Greyhounds and male dogs of any large or giant breed are at higher risk of developing osteosarcoma (bone cancer), especially in their lower legs.