THE MALIGNANT POTENTIAL OF CARDIAC MYXOMAS

Cardiologists rarely encounter tumoral pathology, the commonest being the myxoma which presents more often as cardiac rather than neoplastic disease. A few cases of "malignant or metastatic cardiac myxoma" have been reported in the literature. We have not observed this behaviour in the follow-up of 100 cases of myxoma between 1959 and 1989. However, during the same period, 14 intracardiac sarcomas (operated or not) were seen, which were all rapidly fatal. A critical review of the cases of metastatic cardiac myxomas reported in the literature enabled us to classify them into three groups: the first, 9 cases of false myxomas. They were cardiac sarcomas and therefore a histopathological diagnostic error had been made. The second group comprised false metastases. They concerned arterial embolism of fragments of myxoma causing ischemic infarction or infiltration of the arterial wall by the myxoma, damaging the artery and resulting in fusiform aneurysm. This cannot be accepted as a true metastasis: a number of examples are given as they are too many to be named individually. The cardiac and cutaneous myxomas observed in Carney's complex may be included in this category. The third group has to be discussed case by case: these "metastatic myxomas" can all be explained logically and malignancy can be excluded; they are few in number (5 cases!) but often published several times by different authors. In our opinion, a carcinologically "malignant" metastatic myxoma remains a questionable pathological entity. This does not mean that a myxoma cannot be lethal: its intracardiac position may cause fatal valvular obstruction, or it may give rise to fatal embolism. Secretion of interleukine 6 may generate severe general immunopathological states. In Carney's complex, intracardiac recurrences are especially common. However, these tumours remain fundamentally different from intracardiac sarcomas, which are still untreatable; myxomas can generally be cured by cardiac surgery.