Chondrosarcoma accounts for 5-10% of bone tumours in the dog and is second in incidence to osteosarcoma. It is localised in 61% of the cases in flat bones. It may develop in the nasal cavities (a frequent site in the dog), axial skeleton (ribs, facial bones) (Fig. 1) and appendicular skeleton and also in extraosseous sites (breasts, heart valves, aorta, larynx, lungs, omentum). Its aetiology is not known, but there are descriptions of the malignancy developing in pre-existing multiple cartilaginous exostoses (Dernell et al., 2007). It is a locally aggressive tumour, but its metastatic potential is relatively low (18-60%); sites of metastatic spread include the lungs, pleura, mediastinum, pericardium, lymph nodes, bone, liver, kidneys, adrenal glands and eyes.
This malignancy affects middle-aged dogs (6-9 years), of medium to large size (approximately 20-30 kg), without a particular predisposition for gender or breed, except for Golden Retrievers. Lesions in appendicular bones are characterized by osteolysis, osteoproduction or mixed pictures, and occur above all in the proximal tibia, and less frequently in the femur and humerus.
Chondrosarcoma is difficult to differentiate radiographically from osteosarcoma but the difference in prognosis between these two types of tumours underlines the importance of reaching the correct diagnosis through a bone biopsy. In the case of chondrosarcoma, amputation of the affected limb has been reported to be followed by a median survival of 979 days, without requiring chemotherapy (Farese et al., 2009). The survival is affected significantly by the histological grade (grade III is more aggressive and associated with a worse prognosis than grades I and II). Chondrosarcoma may also develop in the ribs and accounts for 28-35% of costal tumours. The prognosis of chondrosarcoma in this site is also excellent with a reported survival after only wide margin excision of 1080-3820 days (Pirkey-Ehrhart et al., 1995; Liptak et al., 2008).
Chondrosarcoma is relatively common in cats in the femur, scapula and pelvis. If the tumour is excised completely, the animal can survive a long time without requiring chemotherapy.
Suggested readings
- 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.
- Farese, J.P., Kirpensteijn, J., Kik, M., Bacon, N.J,, Waltman, S.S., Seguin, B., Kent, M., Liptak, J., Straw, R., Chang. M.N., Jiang, Y., Withrow, S.J., 2009. Biologic behavior and clinical outcome of 25 dogs with canine appendicular chondrosarcoma treated by amputation: a Veterinary Society of Surgical Oncology retrospective study. Veterinary Surgery 38(8),914-9.
- Liptak, J.M., Kamstock, D.A., Dernell, W.S., Monteith, G.J., Rizzo, S.A., Withrow S.J., 2008. Oncologic outcome after curative-intent treatment in 39 dogs with primary chest wall tumors (1992-2005). Veterinary Surgery37(5),488-96.
- Pirkey-Ehrhart, N., Withrow, S.J., Straw, R.C., Ehrhart, E.J., Page, R.L., Hottinger, H.L., Hahn, K.A., Morrison, W.B., Albrecht, M.R., Hedlund, C.S., 1995. Primary rib tumors in 54 dogs. Journal of American Animal Hospital Association 31(1),65-9.