Cardiac myxoma: morphologic, histochemical, and tissue culture studies.

Twenty-one cases of cardiac myxoma exhibiting a variety of histologic findings were investigated by light and electron microscopy, tissue culture, and immunohistochemical studies for factor VIII-related antigen (FVIII-RA) and Ulex europaeus 1 (UEA-1) lectin. The cardiac myxoma cells revealed variable cellular arrangements, and some tumor cells revealed vascular-like channels. Immunohistochemically, FVIII-RA was found only in the endothelial-like cells covering the vascular-like channels or slits, whereas UEA-1 lectin reacted not only with myxoma cells having luminal structures or network-like arrangements but also with single cells. On electron microscopy, some myxoma cells revealed differentiation into cells forming vascular structures. In tissue culture, the tumor cells were polygonal and proliferated with extensions of the cytoplasmic processes. Arrangements suggesting vascular channels or slits were not observed. In a coculture of tumor cells and blood clot, the tumor cells covered the surface of the clot. However, angiogenesis was not observed in the tissue culture study. The results of our studies were inconclusive regarding the histogenesis of cardiac myxomas, but it was considered that cardiac myxoma is a neoplasm arising from mesenchymal cells with vasoformative characteristics.