Embryonal rhabdomyosarcomaAn ultrastructural study

Ultrastructural analysis of an embryonal rhabdomyosarcoma has revealed immature rhabdomyoblasts with an abundance of cytoplasmic organelles and membranous systems. More mature elements demonstrated progressive accumulation of cytoplasmic fibers which ultimately occupied the greater part of the cytoplasmic substance. Even within the largest cells encountered, however, the definitive banding of striated muscle was not observed. Characterization of the neoplasm as myosarcomatous was not possible on the basis solely of ultrastructural morphology. It is felt that the electron microscope will offer scant prospect of success in the differentiation from one another of anaplastic soft part sarcomas which have escaped definitive identification by conventional methods.