Intracysternal crystalline cytoplasmic inclusions in a cardiac myxoma.

Electron microscopy of an atrial myxoma removed at surgery from a 56-year-old woman revealed unusual intracysternal inclusions in the cytoplasm of tumor cells. These structures appeared in the rough endoplasmic reticulum and consisted of multilaminar arrays of crystalline plates of regular periodicity, about 10 nm apart. Although crystalline and other intracysternal inclusions may occur in different pathologic disorders, their occurrence in an atrial myxoma is a hitherto unreported observation.