Canine Fibrosarcomas: Oropharyngeal, Bone and Nervous System Fibrosarcomas

Fibrosarcomas are fast-growing malignant tumors. This condition can 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. They rarely spread (about 10%). The average age of animals affected by fibrosarcoma is about 8 years. However, this type of tumor has been seen in dogs less than 1 year of age.

Oropharyngeal Fibrosarcoma

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.

Fibrosarcomas of Bone

Fibroblastic bone tumors may develop from the periosteal tissue (periosteum is 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 majority of domestic animal species in the head bones, especially in the upper and lower jaws, sometimes in long bones. Periosteal fibrosarcoma result 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 is rarely reported in other domestic animals. The most common are located in long bones, having an invasive and destructive character. These tumors produce bone destruction over a period of several months to a year, and are generally slower to metastasize than primary osteosarcoma of bone.⁴

Neurofibrosarcoma

Neurofibrosarcoma has been almost exclusively reported in dogs, and extremely sporadically in other species, such as horses and felines; it usually involves the brachial plexus (an arrangement of nerve fibers, running from the spine into the front limba) 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

References: REF FILE #4128