Advice from Vet Dr. Patrick McHale, CVM from the http://www.dog-health-guide.org/caninecancer.html on treating dog cancer and tumors. Tumors are not always cancerous. Frequently tumors consist of fatty tissue and are not cancerous or benign. When a vet sees cancer, the most common type is lymphosarcoma, which effects the lymph nodes. Some types such as bone cancer are extremely aggressive. Dogs tend not to get ill like human patients. Treatment needs to begin immediately in more aggressive types of cancer. Not every owner opts to select aggressive treatment due to the need to be in an unfamiliar facility for up to 6 weeks as well as the cost. The prognosis for each type of cancer is another factor that needs to be considered by owners.