The diagnostic usefulness of electron microscopy investigation of orbital embryonal rhabdomyosarcomas.

The ultrastructural study of three malignant orbital tumors, only one of which was correctly diagnosed as embryonal rhabdomyosarcoma upon histologic examination, is reported. In all 3 cases electron microscopic investigation revealed the presence of rhabdomyoblasts. These are easily recognizable in one case in which the diagnosis was made on the basis of the optical microscopic study. The other two cases needed further tests to evince rhabdomyoblasts. The importance of an ultrastructural study for a histogenetic characterization of this kind of tumor is emphasized. As far as embryonal rhabdomyosarcomas are concerned the electron microscopic study is possible, and it gives useful results even when material fixed with routine histologic methods (formalin, Bouin's solution) are used.