XXXX : a clinicopathologic and electron microscopic study.

@entity1 @entity5 @entity4618 @entity2916 @entity299 @entity4607
@entity299 are rare @entity5 of infancy. In a series of 36 @entity1 78 percent were under 1 year of age, and only one @entity1 was over age 15 years. Ninety percent of the @entity4618 were multiple and occurred with nearly equal frequency in the right and left ventricles. Although reportedly infrequent in the atria, @entity4618 involved either one or both atria in 30 percent of @entity1 . In 50 percent of @entity1 at least one of the @entity5 masses was intracavitary and obstructed 50 percent or more of one of the cardiac chambers or valve orifices. Symptoms referable to obstruction of intracardiac blood flow were present in nine @entity1 , none of whom had @entity2916 , and all of whom would appear to have been good surgical candidates. Histologically the @entity4618 were composed of classic "spider cells". Electron microscopic studies revealed scattered bundles of myofibrils ringing these cells and radiating toward the center; glycogen was present both free in the cytoplasm and within mitochondria. Distinct intercellular junctions resembling intercalated discs with well defined desmosomes and nexuses were present. Many of the cells contained leptofibrils, arranged either peripherally or in spiraled clusters in the center of the cell. @entity4618 derive from cardiac muscle cells and appear to represent @entity4607 rather than true @entity5 .
