Cutaneous myxosarcoma with pulmonary metastases in a dog.

The pathological findings in a 13-year-old dog with cutaneous myxosarcoma with pulmonary metastases are described. Grossly, there was a large subcutaneous mass in the right scapular region, a smaller nodule in the caudal abdominal region and a fibrotic mass at a fracture site in the right hindlimb. Radiographic examination revealed several pulmonary nodules. Microscopical evaluation revealed a myxosarcoma characterized by the proliferation of spindle to stellate cells with multiple prominent nucleoli and vascular invasion. The neoplastic cells were haphazardly arranged in a mucopolysaccharide matrix. Immunohistochemically, the neoplastic cells expressed vimentin, but not cytokeratin or glial fibrillary acidic protein. There was restricted expression of desmin, smooth muscle actin and S-100 protein.