Bone Cancer in Dogs
Bone Cancer in Dogs
The lung is the most common location for metastatic osteosarcoma. Pulmonary metastases (also known as “lung metastases” or “lung mets”) can be asymptomatic early on. They can be detected on chest radiographs or computed tomography (CT) scanning. Chest x-rays are part of the initial evaluation when a dog is diagnosed with osteosarcoma, but visible metastases at that stage are only visible in 10 percent of cases. Three radiographs of the chest are usually done as the initial screening for lung metastases.
Symptoms of Lung Metastases
Pulmonary metastases may not produce symptoms. However, as the nodules grow, most dogs will slow down and may start showing flu-like symptoms. Runny nose and runny eyes are possible.
If lung metastases are close to the main bronchial tubes or near the nerves of the diaphragm, they can cause irritation, which can cause a cough. There are other reasons for a cough – reflux of acid from the stomach can do it, such as heartburn. A reverse sneeze can sound like a cough, and sometimes mild forms of laryngeal paralysis can cause a cough, usually after eating or drinking. Suppressing the cough may help with symptoms.
Another sign of metastases in the lungs occurs when fluid builds up around the lungs.
The lungs are covered in two layers of a thin lining (called “pleura”). One layer covers the lung itself; the other covers the inside of the rib cage. The two are virtually inseparable and contain only enough fluid to allow for them to move smoothly against each other.
When the lining gets infected, inflamed or involved with cancer cells, it develops small holes through which fluid leaks – fluid then accumulates between the two layers. This is called “pleural effusion.”
When this happens, fluid accumulates against the lungs, not inside them, and compresses the lungs, making it harder for them to expand with air. If the effusion is caused by cancer (known as “malignant effusion”), the fluid accumulates quickly.
Palliative measures such as use of diuretics or drainage of the fluid may help for a short period of time, but the fluid tends to recur quickly. This is different from metastases in the lungs themselves, which can go for a long time without causing symptoms.
Hypertrophic Osteoarthropathy (HO)
Hypertrophic osteoarthropathy is defined as the bilateral, symmetrical soft tissue swelling of the limbs. Lung metastases are the most common cause of HO. The limbs may be warm to the touch and are often painful when pressed. The dog may be reluctant to move and may show signs of lameness.