Metastasising osteosarcoma in an eastern white pelican (Pelecanus onocrotalus)

Abstract

A 15-month old captive born Eastern white pelican (Pelecanus onocrotalus) with an abnormal gait had a firm swelling of the right stifle that was unresponsive to conservative treatment with NSAIDs. Radiography of the leg showed disruption of the osseous detail of the distal femur and proximal tibiotarsus with a marked periosteal reaction, marked soft tissue swelling surrounding the right stifle and mottled increased radiodensity of these soft tissues. Despite medical treatment, the immobility of the leg progressed, inappetence set in and the bird was euthanased.  On post-mortem examination there was a large ossified mass at the right stifle and additional well circumscribed masses were evident in the leg and wing musculature, pectoral muscles and myocardium. Further masses were present in the liver and in one kidney. Histological examination identified the stifle mass as an osteosarcoma. The various masses found in the musculature, liver and kidney were constructed of similar cells and considered metastases. The predilection of the metastases for muscular tissue, including the myocardium, is unusual and has not previously been described in birds.