Characterization of myxoid substance of human aortic sarcoma

An autopsy case of aortic sarcoma which was located in the intima of the abdominal aorta and characterized by abundant extracellular myxoid substances was examined. Histological, immunohistochemical and ultrastructural studies revealed no characteristics suggestive of endothelial, leiomyogenic or histiocytic differentiation. Histochemical and biochemical analyses revealed that the myxoid substances were glycosaminoglycans (GAGs) consisting of hyaluronic acid (85% of the total GAG) and chondroitin sulfate proteoglycan (15% of the total GAG). Neither heparan sulfate proteoglycan nor dermatan sulfate proteoglycan was detected. In the aorta, GAGs are synthesized mainly by arterial smooth muscle cells and endothelial cells. Among these cells, the arterial smooth muscle cell is the principal cell type that synthesizes aortic GAGs, predominantly chondroitin sulfate proteoglycan, whereas the endothelial cell synthesizes small amounts of GAGs, predominantly heparan sulfate proteoglycan. Therefore, the results of this study suggest that the tumor cells of the present case have a property similar to arterial smooth muscle cells in terms of GAG synthesis, and that the tumor originated most probably from arterial smooth muscle cells.