Myxoid leiomyosarcoma of the left atrium: a rare malignancy of the heart and its comparison with atrial myxoma

Primary tumours of the heart are rare. The majority of these tumours are benign, with myxomas located in the left atrium being the most common form. Almost all malignant tumours are sarcomas and occur preferentially in the right side of the heart. An exception to this rule is leiomyosarcoma, a rare form of primary cardiac sarcoma that occurs predominantly in the left atrium, as does cardiac myxoma. The case of a 53-year-old woman who presented with symptoms of mitral valve stenosis and pulmonary hypertension is reported. Cardiac catheterization, angiography and echocardiography revealed a left atrial mass that was interpreted as atrial myxoma. At the time of operation, the myxoid appearance of the tumour mass further supported this assumption. The tumour, including a wide rim of atrial septum, was removed with cautery. Histopathological examination unexpectedly showed that the tumour was not an atrial myxoma but rather a myxoid variant of a primary leiomyosarcoma. Immunohistochemistry and electron microscopy confirmed the diagnosis. Local radiotherapy was considered but deemed contraindicated in view of the longstanding pulmonary hypertension. Two months after excision, a repeat echocardiogram indicated recurrence of tumour in the left atrium, and the patient died a few days later. The preferential left atrial location and the frequently myxoid appearance of primary leiomyosarcomas of the heart make it particularly difficult to differentiate them preoperatively from atrial myxomas. The authors recommend resection of all atrial myxoid tumours with a wide (at least 1 cm) margin, combined with intraoperative frozen section diagnosis, because complete surgical resection appears to correlate with prolonged survival in the few reported cases of atrial leiomyosarcomas. In cases of incomplete initial resection or local recurrence in the absence of metastatic disease, heart transplantation may be a valid option in appropriately selected patients.