Cancer is an all too common problem in many breeds, including Mastiffs.  While much research is being done, most types of cancer in dogs are poorly understood and treatment options are often limited. 

Lymphoma (cancer of the lymph glands) and osteosarcoma (bone cancer) are among the tumors that are commonly seen in dogs.  

• Lymphoma accounts for approximately 20% of all canine tumors, and >80% of cancers originating from blood cells. Most of the time, lymphoma appears as swollen glands (lymph nodes) that can be seen or felt under the neck, in front of the shoulders, or behind the knee.
• Occasionally, lymphoma can affect lymph nodes that are not visible or palpable from outside the body, such as those inside the chest or in the abdomen. In these cases, dogs may accumulate fluid in the chest that makes breathing difficult, or they may have digestive problems (diarrhea, vomiting, or painful abdomen). If left untreated, dogs with lymphoma will generally succumb to the disease within 3 to 4 weeks

• Osteosarcoma accounts for 85% of skeletal cancers. Large and giant breed dogs are at highest risk for developing osteosarcoma, possibly due to the fact that bone cells at the growth plates must divide many times to create the very long bones that are characteristic in these breeds. However, there probably are additional risk factors, which have yet to be defined. Osteosarcomas generally occur in the limbs, however, these tumors can arise anywhere in the long bones, as well as in flat bones (ribs, skull, and spine).

• Osteosarcoma is always a life-threatening disease because it is highly metastatic, making treatment of this type of cancer especially difficult. The standard of care for osteosarcoma of the limbs includes amputation or limb-sparing surgery, followed by adjuvant chemotherapy. The median survival for dogs with osteosarcoma treated with surgery alone is approximately 100 days.