Cytology of embryonal rhabdomyosarcoma: a cytologic, light microscopic, electron microscopic, and immunohistochemical study of seven cases.

A correlated cytologic and histologic study of seven cases of embryonal rhabdomyosarcoma is presented. The diagnosis of rhabdomyosarcoma was established by light and electron microscopy and immunohistochemistry of the operative specimens. The cytologic appearance of the smears corresponded well with the histopathologic findings. Cytologically, two main cell types were distinguished: a predominant primitive, small round cell with scant cytoplasm and a large cell with an abundant cytoplasm, sometimes tadpole- or ribbon-shaped. The tumor cells were often enclosed in a background of mucosubstances. The lack of cytologic features proving rhabdomyoblastic differentiation, such as cross-striation, necessitates the use of additional methods in the cytologic diagnosis of embryonal rhabdomyosarcoma. The value of the embedding technique for ultrastructural analysis and immunohistochemistry in the demonstration of desmin in aspirates is emphasized in the diagnosis of embryonal rhabdomyosarcoma.