A mixed mesenchymal sarcoma in the soft palate of a dog: light and electron microscopic findings.

Soft tissue tumors containing a mixture of neoplastic fibrous tissue, cartilage, and bone have previously been classified as extraskeletal osteosarcomas in the dog. These tumors are often poorly differentiated, contain multiple neoplastic cell types, and might be more appropriately called mixed mesenchymal sarcomas. The present neoplasm caused clinical signs of stridorous respiration and dysphagia in a four and one-half year old dog. Four neoplastic cell types were demonstrated by light and electron microscopy.