Usefulness of immunohistochemical testing and electron microscopy in the diagnosis of embryonal rhabdomyosarcoma.

Background: This article presents the results of histological, immunohistochemical, and ultrastructural examinations of embryonal rhabdomyosarcoma.

Material/methods: 20 tumors were tested histologically, 13 immunohistochemically, and 5 under electron microscopy.

Results: We found that in cases when the entire tumor or large specimens were obtained for estimation, it was possible by examining many areas of the neoplasm to establish a diagnosis on the basis of testing paraffined sections, routinely HE stained. Our evaluation of the value of certain additional histological methods indicated only slight diagnostic usefulness for tumors of this kind. Among the immunohistochemical methods we evaluated, the desmin assay had the greatest practical applicability, due to the fact that this antigen is also expressed in highly immature cells; in second place was myoglobin. Differences are pointed out in the results obtained by assaying myoglobin using DAB and the DAKO kit. Ultrastructural examinations revealed myofilaments of myosin and actin in all types of cells, including immature cells. Particular attention is drawn to the possibility of using material fixed in formalin for ultrastructural examination. The preservation of intact myofilaments in material prepared in this way constitutes an essential diagnostic aid.

Conclusions: In diagnosing embryonal rhabdomyosarcoma the most useful examination, apart from histological examination, is electron microscopy, followed by immunomorphological examination.