Abstract
We describe a primary malignant mesenchymal tumor of the heart in an 8-year-old miniature Schnauzer that was euthanatized because of poor prognosis. At necropsy, multiple milky-white masses of various sizes were seen to project from the endocardium into the right atrial and both ventricular cavities. On histopathological examination, the cardiac neoplasia was diagnosed as primary malignant peripheral nerve sheath tumor. There have been no previous reports of such a tumor occurring in the canine heart.
