A comparative study on morphology and immunohistochemistry of rhabdomyosarcoma and embryonal skeletal muscles

To investigate the histologic and histogenetic relationship between various types of rhabdomyosarcomas (RMS) and embryonal skeletal muscle (ESM) for further understanding of the histogenesis, classification and pattern of differentiation of RMS. Fifty cases of variant types of RMS and 20 cases of ESM at different gestational ages were available. All specimens were stained with HE, PAS, Van Gieson, Masson, phosphotungstic acid hematoxilin and with antibodies for the demonstration of vimentin, desmin, HHF-35 and myoglobin by ABC method. The results showed that the order of positive expression and the intensity of positive reaction of the different immunohistochemical staining were consistent with the degree of differentiation of the tumor and the development of the ESM. It is obvious that each type of RMS is composed of tumor cells in different degree of differentiation and is derived from primitive mesodermal cells which are capable of potential differentiation towards mature skeletal muscles. Based on the results of this study, an ideal histologic classification of RMS should reflect not only the cell morphology and histologic structures but also the degree of differentiation of the tumor cells.