Fibrosarcomas are fast-growing malignant tumors, which may occur in any area of the body with most common sites being mouth, mammary glands, trunk, and legs. Fibrosarcomas vary greatly in size and appearance, but only 10 percent of them spread. The average age of animals affected by fibrosarcomas is about 8 years, although these tumors have been seen in dogs less than 1 year of age.
Oropharyngeal fibrosarcoma is the third most common malignant tumor of the canine oral cavity. It tends to occur in younger dogs; the mean age of onset is 7.5 years, but about 25% occur in dogs under 5 years of age. Male retriever dogs seem to be affected more often than females. The tumor most commonly involves the tissues of the upper jaw, nose, lips, tongue, and palate. It appears as a firm, smooth mass. Although metastasis occurs only in about 25% of cases, the tumor extensively infiltrates adjacent tissues, making the treatment difficult.1 Surgery is the treatment of choice. Recurrence is common within 1 year of surgery. Secondary tumors are usually in the lungs, but may be widespread.3 Radiation and chemotherapy is recommended, if the tumor is impossible to remove or cannot be removed completely. In dogs with oral fibrosarcomas radiation and aggressive surgery may result in survival times of several months.
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Fibrosarcomas of bone may develop from the periosteal tissue (a membrane that lines the outer surface of all bones), or the stromal tissue of the medullary canal. The medullary location is less frequent, compared to periosteal incidence.5 Periosteal fibrosarcoma is located in the head bones, especially in the upper and lower jaws, sometimes in long bones, and results in bone destruction and fractures. Central (medullary) fibrosarcoma of bone is a malignant tumor of fibrous connective tissue, which is seen primarily in the mature (1 year 6 months to 12 years) male dogs of large and medium breeds. This type of tumor has an invasive and destructive character and produces bone destruction over a period of several months to a year, but is generally slower to metastasize than primary osteosarcoma of bone.4
Neurofibrosarcoma has been almost exclusively reported in dogs, and extremely sporadically in other species, such as horses and cats. It usually involves the brachial plexus (an arrangement of nerve fibers, running from the spine into the front limbs) or lumbar plexus (lower back nerve fibers), and less commonly the cranial nerves. The treatment of nervous system tumors includes a complex of procedures, such as surgery, cobalt 60 radiation, whole body hyperthermia, I125 implants, and chemotherapy. These procedures can be applied alone or in association.5
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