Heterogeneous expression of factor VIII/von Willebrand factor by cardiac myxoma cells

The expression of factor VIII/von Willebrand factor (FVIII/vWF), a marker for endothelial differentiation, was examined immunohistochemically in normal cardiac tissue and seven cardiac myxomas. In normal tissue, FVIII/vWF was detected in the surface endocardial cells and the vascular endothelial cells. In tumors, the isolated myxoma cells and the small groups and cords of myxoma cells did not express FVIII/vWF. Some of the surface cells contained FVIII/v/WF, but most did not. The predominant sites of FVIII/vWF localization were the multilayered, concentric vascular structures. In most of these, FVIII/vWF was present only in the inner layer of cells immediately surrounding the vascular lumens. In some, however, intense staining was present in both the inner and outer cell layers. In general, the FVIII/vWF-positive cells had the appearance of endothelial cells. These observations correlate with the recognized histologic, histochemical, and ultrastructural heterogeneity of cardiac myxoma cells, and conform to the current view that such cellular heterogeneity arises via the divergent differentiation of multipotential mesenchymal cells.