Chondrosarcoma in a captive giant anteater (Myrmecophaga tridactyla).

The development of neoplasms in giant anteaters (Myrmecophaga tridactyla) is poorly documented, with most studies focused on non-neoplastic changes. This report describes a case of chondrosarcoma in a 15-year-old male captive giant anteater that presented with lameness for approximately 6 months, locomotion difficulties and swelling of the left thoracic limb. After review of a radiograph, humane euthanasia was decided due to the poor prognosis and quality of life. At necropsy, a 17 × 20 × 13 cm mass was seen to project from the humeroradioulnar joint of the left thoracic limb. The mass was white, firm to soft, with translucent areas and moderate multifocal irregular cavitations. Histologically, it consisted of a poorly demarcated and partially encapsulated malignant mesenchymal neoplasm, arranged in irregular lobules of varying sizes containing hyaline cartilage. Immunohistochemical analysis revealed moderate immunolabelling of vimentin in neoplastic mesenchymal cells but no immunolabelling for pan cytokeratin. Based on the macroscopic, histopathological and immunohistochemical findings, a diagnosis of chondrosarcoma was established. This case emphasizes the importance of diagnosing diseases in captive species in which pathological conditions are rarely documented. This appears to be the first reported case of chondrosarcoma in a giant anteater.