Fibrosarcoma is a relatively rare kind of cancerous tumor that develops in the connective tissues and bones of the skeleton. It is most commonly seen in the pelvic area, the spine, skull, and the ribs but can occur in any bone and connective tissue throughout the body. Younger dogs can sometimes develop a very rare type of fibrosarcoma in the mouth and this is more common than the skeletal fibrosarcoma.

Fibrosarcoma in the mouth is often first misdiagnosed as a dental health problem since it is associated with swollen and bleeding gums and lumps along the jaws, under the tongue or towards the back of the mouth. Usually vets will treat these with antibiotics and anti-inflammatory drugs first, then if they do not respond they perform x-rays of the area and check for tumors. It is also important to realize that this swelling and bleeding can also be caused by the much more common osteosarcoma or bone cancer, however the treatments will be different. A biopsy is the only way for the vet to verify which type of cancer he or she is treating. After the biopsy confirms the finding of fibrosarcoma the vet and owner may decide to proceed with surgical removal of the tumor and surrounding bone, chemotherapy, radiation therapy, and pain management for the dog. In cases where there is significant bone and connective tissue damage surgery may not be a practical option, so chemo and radiation therapies are often used.

For fibrosarcoma in the joints and skeletal areas the symptoms typically include swelling around the bone and connective tissue, lameness, and lethargic behavior as well as sensitivity to touch or pressure on the affected area. Blood tests, urine tests, x-rays, and biopsies are all important to obtain a diagnosis as well as rule out any other health conditions that may be causing the same symptoms. As with tumors in the mouth, the treatment includes surgically removing the tumor and all affected tissue as well as pain management and ongoing monitoring of the dog. Usually this type of bone cancer does not spread to other areas of the body; however, there have been cases where it has.

Caring for the dog in recovery from fibrosarcoma involves several different strategies. The dogs must be kept quiet and calm to allow the incision to heal as well as to prevent any fractures or bone or joint damage due to the cancer weakening the bones in the area of the tumor. In some cases radiation therapy will be used to kill the tumor if surgery is not an option. Not all vet clinics can provide this treatment so owners may have to transport their dog to a clinic that can. Dogs will also be on pain medications and drug therapies and may also be placed on food supplements and dietary restrictions during their recovery period. Some pets will also need rehabilitative therapy to help them adjust to moving after surgery and to prevent any bone fracture after the surgery.