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1 June 2010 Rhabdomyosarcoma in a Yellow-Headed Caracara (Milvago chimachima)
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Rhabdomyosarcoma is a malignant tumor originating from rhabdomyoblasts that is rarely reported in domestic animals or in free-living and pet birds. This paper presents a case of rhabdomyosarcoma in a free-ranging yellow-headed caracara (Milvago chimachima), originating from the muscle region of proximal left humerus, with metastases in the left pectoral muscles, heart, lungs, and proventriculus. The cytology was suggestive of rhabdomyosarcoma because of malignant features and cytoplasmic cross-striations in cells. The histopathologic examination revealed neoplastic proliferation composed of spindle cells arranged in irregular sheets or bundles with marked cellular pleomorphism, moderate mitotic ratio, and multinucleated giant cells. Some neoplastic cells also presented evidence of scant cytoplasmic cross-striations visible at histologic sections stained by hematoxylin and eosin and phosphotungstic acid hematoxylin. Immunohistochemically, tumors cells were positive for desmin and negative for α-smooth muscle actin and S100 protein.

Ana Carolina H. Maluenda, Renata A. Casagrande, Cristina T. Kanamura, Luciana N. Torres, Fausto Quagglia Neto, Marcelo S. Gomes, and Eliana R. Matushima "Rhabdomyosarcoma in a Yellow-Headed Caracara (Milvago chimachima)," Avian Diseases 54(2), 951-954, (1 June 2010).
Received: 15 September 2009; Accepted: 1 November 2009; Published: 1 June 2010

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