Poorly differentiated sarcoma involving the mitral valve in a golden retriever

A six-year-old male, neutered Golden retriever was presented to the University of Minnesota Veterinary Medical Center Cardiology Service for exercise intolerance, two collapsing episodes, and a newly diagnosed heart murmur. Echocardiogram revealed an intracardiac mass within the left ventricle causing severe left ventricular outflow tract obstruction. The patient re-presented a few weeks later for respiratory distress and was euthanized. At necropsy, a large multilobular mass was noted, which coursed along the mitral valve base and was firmly adhered to the endocardium of the left ventricle. Histology and immunohistochemical staining were consistent with a poorly differentiated sarcoma.