Cardiac myxoma with chondroid features: a light and electron microscopic study.

The first case of a cardiac myxoma exhibiting chondroid differentiation is described. The tumor showed lacunar spaces around clusters of typical myxoma cells on light microscopy. Ultrastructurally the tumor cells contained abundant glycogen, and the tumor stroma contained proteoglycan granules identical to those seen in the ground substance of cartilage. These findings lend further support to the belief that the primitive mesenchymal cell is the cell of origin in cardiac myxoma.