Intracardiac myxoma.

Six intracardiac myxomas and 2 thrombi were subjected to scanning electron microscopy (SEM). Surface morphology of myxomas was distinct from thrombi. The surface of myxoma was either smooth or thrown into projections which had a continuous endothelial lining. This was lacking in thrombi. Cut surface of myxoma revealed the presence of round to polyhedral cells having blunt villi and/or pit-like depressions on their surface in a stroma of fibres, granular material and blood vessels. Thrombi were composed of blood elements enmeshed within fibres. No cells of the type encountered in myxomas were present.