Meningeal rhabdomyosarcoma. Report of a case with cytologic, immunohistologic and ultrastructural studies.

Primary rhabdomyosarcoma of the meninges, a very rare brain tumor, is reported. Cytologic findings by squash preparation were useful as an adjunct to frozen section diagnosis during surgery. The cytologic features of rhabdomyosarcoma without cross-striation have some similarities to those of gemistocytic astrocytomas and anaplastic meningiomas, but the cytoplasmic filaments of rhabdomyosarcoma are different from those of gemistocytic astrocytoma and anaplastic meningioma. Histologically the tumor was embryonal rhabdomyosarcoma with a partially botryoid pattern. The tumor cells have no cross-striations but react positively to antimyoglobin serum on immunoperoxidase staining. In this case, intracytoplasmic filaments resembling poorly formed myofibrils were found on electron microscopic study. The histologic and immunohistologic findings suggest that this rare mesenchymal malignancy might arise from primitive totipotential cells.