Histogenesis of Alveolar Soft Part Sarcoma

In order to clarify the histogenesis of alveolar soft part sarcoma (ASPS), an immunohistochemical and biochemical study was performed on three cases. The immunohistochemical study indicated the presence of actin, desmin, vimentin, and Z-protein in all cases. On the other hand, intermediate filaments other than desmin and vimentin were not detected immunohistochemically. The presence of desmin and Z-protein strongly suggests the myogenic character of this tumor. As to whether ASPS shows striated muscle differentiation or smooth muscle differentiation, the immunohistochemical absence of myoglobin in the three cases suggests that the tumor does not differentiate in the direction of striated muscle. However, biochemical assay of subunits of enolase revealed significantly high amounts of beta-enolase, which is known as a marker for striated muscle, in all three cases. The determined values--735, 426, and 584 ng/mg of protein --are indicative of striated muscle differentiation. In addition, the immunohistochemical study of all cases revealed the presence of beta-enolase in tumor cells. These data definitely show the myogenic character and rhabdomyoblastic differentiation of ASPS.