Fibroblastic osteosarcoma in a white-eared opossum (Didelphis albiventris)

Osteosarcoma is characterized by the production of osteoid or woven bone, using neoplastic osteoblasts. It is the most common primary bone neoplasm in canines and humans. This neoplasm was previously reported in all vertebrate classes, including a wide variety of mammals. However, there is no case report describing this neoplasm in Didelphis albiventris. Therefore, the objective of this manuscript is to describe the clinical-pathological aspects of fibroblastic osteosarcoma in D. albiventris. A wild adult male white-eared opossum (D. albiventris) arrived at the zoological park of the “Universidade de Caxias do Sul” with a swollen left thoracic limb. After a general clinical examination, the animal was transferred to the Veterinary Clinic of “Universidade de Caxias do Sul” for radiographic examination of the left thoracic limb and thorax. Additionally, some material was collected through fine needle aspiration (FNA) for cytologic evaluation. The radiographic findings and cytologic evaluation indicated osteosarcoma. The animal was euthanized due to severe clinical conditions and guarded prognosis. During necropsy, macroscopic analysis of the viscera was performed, fragments of various organs were collected and fixed in 10% neutral buffered formalin. All fragments were processed following routine histological techniques. The histopathological evaluation confirmed osteosarcoma, which was classified as a fibroblastic subtype. Case reports are crucial for the knowledge of incidence, prevalence, and behavior of the current mentioned disease, as well as other diseases, in species with such limited information. In order to obtain a decisive diagnosis, a few different examination methods were associated. Although the observations presented are based on a single case, this neoplasm had a similar clinical presentation to that described in other species. RESUMO: O osteossarcoma é caracterizado pela produção de osteoide ou osso imaturo, por osteoblastos neoplásicos. É a neoplasia óssea primária mais comum em caninos e humanos. Essa neoplasia já foi relatada em todas as classes de vertebrados, incluindo uma grande variedade de mamíferos. Não havendo descrição dessa neoplasia até o momento em Didelphis albiventris. O objetivo deste trabalho é descrever aspectos clínico-patológicos de um caso de osteossarcoma fibroblástico em D. albiventris. Chegou para atendimento no Zoológico da Universidade de Caxias do Sul um gambá-de-orelha-branca (D. albiventris), macho, adulto, de v