Multilobular tumour of bone (multilobular osteochondrosarcoma, previously known as chondroma rodens) is a rare bone tumour characterized by slow growth; it is locally invasive and potentially metastatic, especially to the lungs. It affects medium- and large-sized breeds of dogs and, usually, elderly subjects. No predisposition for sex or breed has been found.
The sites most commonly affected are the flat bones of the skull (temporal and occipital bones, zygomatic process, orbit, frontal bone), the maxilla and the mandible. There are also reported cases of involvement of the hard palate and the os penis.1-3
Radiography, computed tomography and nuclear magnetic resonance imaging studies show that these tumours are characteristically compact, radio-dense masses, with well-defined margins and evident internal areas of granular calcification; the lysis of adjacent bony structures is often very marked (Fig. 1).4,5
The diagnostic approach is similar to that described for appendicular osteosarcomas. In addition to bone deformation neurological signs may be present, secondary to direct expansion of the mass into the central nervous system.
The prognosis is variable and depends on the site of the tumour and whether surgical excision with wide margins is possible. Recurrences are possible following limited resection of margins and can occur even a very long time after surgery (47-58% of relapses occurred between 420 and 797 days after surgery).6,7 The same can be said for metastases, as metastatic spread was reported in 56-58% of subjects between 420 and 542 days after diagnosis.6,7 Treated dogs may survive for a long time (630-797 days).6,7
Radiotherapy and chemotherapy have been combined with surgery; however, the real efficacy of such interventions on relapses, metastases or eventual prolongation of survival is not known.
References
- Banks, T.A., Straw, R.C., 2004. Multilobular osteochondrosarcoma of the hard palate in a dog. Australian Veterinary Journal 82(7), 409-12.
- Dernell, W.S., Straw, R.C., Cooper, M.F., Powers, B.E., LaRue, S.M., Withrow, S.J., 1998. Multilobular osteochondrosarcoma in 39 dogs: 1979-1993. Journal of American Animal Hospital Association 34(1),11-8.
- Dernell, W.S., Ehrhart, N.P., Straw, R.C., Vail, D.M., 2007. Tumors of the skeletal system. In: Withrow, S.J., Vail, D.M. (Eds.), Withrow and MacEwen’s Small Animal Clinical Oncology. Saunders, Elsevier, St. Louis, MI, USA, pp. 540-582.
- Dicks, N., Boston, S., 2010. The use of an angularis oris axial pattern flap in a dog after resection of a multilobular osteochondroma of the hard palate. Canadian Veterinary Journal 51(11),1274-8.
- Hathcock, J.T., Newton, J.C., 2000. Computed tomographic characteristics of multilobular tumor of bone involving the cranium in 7 dogs and zygomatic arch in 2 dogs. Veterinary Radiology and Ultrasound 41(3),214-7.
- Webb, J.A., Liptak, J.M., Hewitt, S.A., Vince, A.R., 2009. Multilobular osteochondrosarcoma of the os penis in a dog.Canadian Veterinary Journal 50(1),81-4.
- Straw, R.C., LeCouteur, R.A., Powers, B.E., Withrow, S.J., 1989. Multilobular osteochondrosarcoma of the canine skull: 16 cases (1978-1988). Journal of American Veterinary Medical Association195(12),1764-9.