Cutaneous Extraskeletal Myxoid Chondrosarcoma with Recurrence and Multiple Pulmonary Metastasis in a Dog

A small cutaneous mass in the right thigh of an 8-year-old, intact male dog was diagnosed as an extraskeletal myxoid chondrosarcoma. Histologically, the neoplasm had lobularity and was characterized by rich myxoid stroma and hypovascularity. The tumor cells displayed polymorphism, and were often arranged in characteristic cords. Immunohistochemically, the tumor cells were positive for vimentin, S-100a, neuronspecific enolase, and synaptophysin. Six months after the surgery, no recurrence or metastasis were observed; however, a large recurrent tumor in the right thigh extending to the abdomen and multiple pulmonary tumors were found in the dog 15 months after the surgery. The necropsy confirmed that the recurrent and pulmonary tumors were the same as the primary tumor and did not involve any cartilage or bone.