title: Rhabdomyosarcoma in a yellow-headed caracara (Milvago chimachima).
abstract: 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 alpha-smooth muscle actin and S100 protein.
authors.affiliation: Department of Pathology, School of Veterinary Medicine, University of São Paulo (FMVZ/USP), Avenida Orlando Marques de Paiva, 87, Cidade Universitária, São Paulo, SP, Cep: 05508-900, Brazil.
authors.forename: Ana Carolina H
authors.initials: AC
authors.lastname: Maluenda
authors.forename: Renata A
authors.initials: RA
authors.lastname: Casagrande
authors.forename: Cristina T
authors.initials: CT
authors.lastname: Kanamura
authors.forename: Luciana N
authors.initials: LN
authors.lastname: Torres
authors.forename: Fausto
authors.initials: F
authors.lastname: Quagglia Neto
authors.forename: Marcelo S
authors.initials: MS
authors.lastname: Gomes
authors.forename: Eliana R
authors.initials: ER
authors.lastname: Matushima
mesh_terms: D000818:Animals; D001715:Bird Diseases / Q000473:pathology*; D046093:Falconiformes; D017809:Fatal Outcome; D012208:Rhabdomyosarcoma / Q000473:pathology / Q000662:veterinary*