Fig. 4

Pathology of tumor in bone marrow. a Biopsied bone marrow contained small round tumors with dense nuclei diffusely aggregated and focally floating within fibrous nests. Immunohistochemical staining for specific hematological lineages were negative for CD3 and CD20, but positive for CD56. b An additional immunohistochemical study suggested positivity for vimentin. Staining for the muscular differentiation markers desmin, myoglobin, and myogenin were positive, whereas CK and MyoD1 were negative. Staining for the neural differentiation markers synaptophysin and S-100 was negative. Original magnification of 40 ×