Canine fibroblastic osteosarcoma: case report and diagnostic approach

Abstract

Osteosarcoma is the most common malignant bone neoplasm in dogs, particularly in large-breed animals, and is characterized by the proliferation of malignant mesenchymal cells with osteoid matrix production. This study aims to report a case of fibroblastic osteosarcoma in a male Flat-Coated Retriever, approximately 8 years old and weighing 33 kg, which presented with progressive lameness of the left thoracic limb. Clinical evaluation included physical examination, hematological tests, and radiographic, electrocardiographic, echocardiographic, histopathological, and immunohistochemical analyses. Radiographic findings revealed bone lysis associated with a proliferative reaction, while histopathology confirmed the presence of characteristic neoplastic cells, with a Ki-67 positivity index of 20%. Treatment consisted of amputation of the affected limb followed by carboplatin chemotherapy administered every 21 days, for a total of six cycles. The patient showed a favorable clinical response, with no radiographic evidence of metastasis to date. It is concluded that early diagnosis, combined with a multimodal therapeutic approach, is essential to improve survival and quality of life in dogs affected by osteosarcoma, and that the association of surgery and chemotherapy represents an effective treatment strategy.