Rare primary sarcomas of the heart.

Three patients with primary malignant cardiac neoplasms are described. All tumors were intracavitary myxomatous masses of the left atrium. Preoperative clinical diagnostic techniques did not indicate malignancy, but suggested mitral stenosis, cor triatriatum, and cardiac myxoma. Grossly, the tumors were sessile rather than pedunculated, and they invaded the underlying structures. Microscopically, although the tumors resembled benign cardiac myxomas, they exhibited mitotic activity and areas of necroses. Ultrastructural examination revealed a spectrum of differentiated mesenchymal cells that lacked the maturation features of cardiac myxoma cells. These gross, microscopic, and ultrastructural features, which suggested the tumors' malignant potential, should help in the early recognition and management of similar tumors.