Osteosarcoma of meninges: clinical, light, and ultrastructural observations of a case.

A primary osteosarcoma of the meninges based on clinical, light, and ultrastructural findings is reported. The neoplasm appears to complete Cushing and Eisenhardt's postulate and expectation of a malignant counterpart of osteoblastic meningioma. The neoplasm lends support to the concept of a primitive multipotential mesenchymal cell in the meninges capable of giving rise to every variety of neoplasms within that potential.