Oral osteosarcoma in dogs is a serious condition. The term osteosarcoma refers to a malignant type of bone tumor. The term oral osteosarcoma indicates that the tumor is located in the mouth, or more particularly, on the upper (maxilla) or lower jaw (mandible). The oral osteosarcoma is classified as axial osteosarcoma or osteosarcoma of the flat bones. It is a mesenchymal tumor characterized by abnormal bone production by the malignantly altered bone producing cells or osteoblasts.
Oral Osteosarcoma in Dogs
In spite of the advances in the veterinary medicine area, the exact etiology of osteosarcoma remains unknown. However, it is postulated that there is a close link between osteosarcoma and several initiating factors like ionizing radiation, genetics, pre-existing bone diseases, trauma, bone viruses and metallic bone implants.
The osteosarcoma, or better said the tumor, initially develops deep within the bone and then it grows outward. Simply put, the bone gets destroyed from the inside out. As the tumor spreads, the condition becomes progressively more painful.
It should be noted that the cancerously altered bone is not as strong as a healthy bone. This means cancerous bones can easily break thus leading to so-called pathologic fractures.
Oral osteosarcoma accounts for approximately percent of all canine cancer cases and it can involve the lower jaw, the upper jaw, or rarely, both jaws. Although it is generally not very common, oral osteosarcoma is still the most common type of bone cancer in dogs. It accounts for about one fourth of all bone cancer cases in dogs.
As a distinct type of tumor, oral osteosarcoma in dogs is an age, sex and breed predisposed condition. Oral osteosarcomas usually develop in dogs that either one year old or dogs that are older than seven years It is confirmed that the risk of developing oral osteosarcomas is slightly higher for males than for females. Studies show that spayed/neutered dogs are at higher risk. This implies that sex hormones offer some form of protection against the disease.
Breeds predisposed to oral osteosarcomas include Rottweilers, Saint Bernards, Great Danes, Golden Retrievers, Labrador Retrievers, Irish Setters and Dobermans. From the listed breeds it can be concluded that oral osteosarcoma is more common in larger dog breeds. Nevertheless, certain small dog breeds like Pugs and Toy Poodles are also predisposed.
At the Vet's Office
When a dog has oral osteosarcoma the owner usually notices the following signs: A mass in the mouth that is visible to the naked eye, swelling of the mouth, excessive drooling, bloody saliva and bleeding from the mouth, halitosis (bad breath), difficulty chewing and difficulty swallowing, decreased appetite, unexplained weight loss, loose teeth, swollen or enlarged areas under the eyes and enlarged lymph nodes under the jawline.
The diagnostic procedure begins with a thorough examination of the dog’s mouth. This phase, depending on the dog’s character and the exact localization of the tumor, may require sedation or anesthesia.
Based on the initial findings, the vet is likely to suggest x-rays. Chest x-rays are useful for determining whether the cancer has spread to the lungs. Mouth x-rays are useful for diagnosing the condition. Unfortunately, the oral x-ray is not enough to properly diagnose the condition unless the disease is in its advanced stages and at least 40 percent of the bone in the mouth is destroyed.
The gold standard for definitive diagnosis is biopsy followed by histological evaluation. What is more, the histological evaluation allows further classification of the different subtypes of oral osteosarcomas.
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In certain cases, some more advanced tests like MRI and CT scans are recommended. In addition of being highly suitable for setting a definitive diagnosis, these tests help determine whether there are metastasis in the nasal cavities, lungs and other areas of the body.
Treatment of Oral Osteosarcoma in Dogs
The first treatment option that comes to mind when speaking about tumors is the combination of chemotherapy and radiation. However, when dealing with oral osteosarcomas they are not option number one. In fact, in patients with oral osteosarcoma, chemotherapy and radiation have variable outcomes.
The treatment of choice for patients with oral osteosarcomas is complete surgical removal of the tumor and its surrounding tissue. Since the tumor does not tend to metastasize, achieving local control through surgical removal is usually enough. In some cases, the surgical approach can be combined with chemotherapy and radiation.
Pain management and maintaining adequate nutrition are the foundation of proper home care for a patient with oral osteosarcomas. Pain management is important since the pain’s debilitating nature can lead to decreased food intake and deterioration of the patient’s overall health status.
If left untreated, the pain of oral osteosarcoma in dogs decreases the patient’s quality of life. When it comes to patients with oral osteosarcomas, adequate nutrition includes high-protein diets and substantial liquid consumption. It has been shown that adequate nutrition maximizes the patient’s response to treatment.
Prognosis of Oral Osteosarcoma in Dogs
Generally speaking, osteosarcomas are aggressive and insidious tumors. However, there are variations between different types of osteosarcomas. For example, when compared to other types, oral osteosarcomas have less aggressive behavior and a less insidious course. Additionally, they have lower tendency towards forming metastasis. Therefore oral osteosarcomas have better prognosis.
Nevertheless the prognosis is directly linked to whether good local control has been achieved. Achieving good local control refers to performing a wide surgical resection with tumor free margins. Simply put, this means complete removal of the tumor and its surrounding tissue.
According to some studies, dogs with osteosarcomas of the lower jaw have a better prognosis than dogs with osteosarcomas of the upper jaw. As contradictory as it may sound, the prognosis is best for dogs with osteosarcomas on both the upper and the lower jaw.
All in all, depending on the oral osteosarcoma’s exact location, the promptness and effectiveness of the treatment, the average survival after surgery is 14-18 months. Oral osteosarcomas rarely have metastasis but they tend to reappear in the mouth even after a complete surgical removal of the initial tumor.
About the Author
Dr. Ivana Crnec is a graduate of the University Sv. Kliment Ohridski’s Faculty of Veterinary Medicine in Bitola, Republic of Macedonia. She is a certified nutritionist and is certified in HAACP food safety system implementation.
She currently practices as a veterinarian in Bitola and is completing her postgraduate studies in the Pathology of Domestic Carnivores at the Faculty of Veterinary Medicine in Zagreb, Croatia.
Ivana’s research has been published in international journals, and she regularly attends international veterinary conferences.