These tumors, which commonly affect the flat bones of the canine skull, are slow growing, locally invasive, and have the potential to metastasize to distant sites, particularly the lungs.
The tumor most commonly affects middle-aged to older, medium- to large-breed dogs and has no apparent sex or breed predisposition. The tumor may be either solitary, a monostotic osteochondroma, or multilobular, polyostotic osteochondromas (osteochondromatosis) or multiple cartilaginous exostosis.
Polyostotic osteochondromas are a heritable entity in dogs.
Clinically affected dogs usually present with multiple soft-tissue masses in the affected area with regional swelling and pain. Symptoms are associated with compression and distortion of adjacent structures. Vertebral osteochondromas usually result in spinal compression with hemiparesis or ataxia. When the CNS is involved, seizures are a common presenting sign.
Diagnosis is based on clinical presentation with supportive radiography which often displays osteolyis of neighboring bone and osteolytic regions associated with the tumor. The tumors usually appear smoothly contoured, nodular subperiosteal masses of dense fibrocartilaginous and osseous tissue.
Pulmonary radiographs are necessary to determine possible secondary metastases. CT scans will assist in the assessment of any intracranial metastases.
A definitive diagnosis requires histopathology.
Treatment usually involves wide-margin surgical resection. In cranial masses, cranioplasty is often required, using polypropylene mesh and polymethyl methacrylate.
Adjuvant therapy including radiation treatment and chemotherapy has been reported, but little is known with respect to its effect on local recurrence, metastasis, and survival time.
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