By immunohistochemistry, tumor cells in 21 of 21 cases were positive for desmin; in 18 of 20 were positive for MYOD1 in a diffuse pattern; in 17 of 19 were positive for myogenin (Figure 1); and in 6 of 11 cases were positive for smooth muscle actin, mostly in a focal pattern. This evidence concerns the gene MYOG and neoplasm.