Cardiac fibrosarcoma in a dog.

A cardiac fibrosarcoma involving the right ventricular free wall, the interatrial septum, and proximal portion of the interventricular septum, with a 2-cm diameter protrusion into the right atrial lumen, was found at necropsy of a 2-year-old Miniature Schnauzer. Severe distortion of the tricuspid valve and narrowing of the aortic and pulmonic outflow tracts had caused the dog to develop right-sided cardiac failure and to have syncopal episodes. A tentative antemortem diagnosis of congenital pulmonic stenosis had been made on the basis of results of physical examination and diagnostic work-up. Evaluation of the case exemplifies the difficulty encountered in diagnosing cardiac tumors before the patient's death.