Mixed malignant mesenchymal tumor of the cerebellar vermis.

In an example of mixed malignant mesenchymal tumor of the cerebellar vermis, striking osteoblastic differentiation was present along with extensive intradural spinal invasion. The CNS sarcomas and their variants are discussed as well as the extraskeletal osteosarcomas. Comparison is made to the teratoid tumors and other mixed and unusual posterior fossa tumor elements, and the capability of midline posterior fossa tissues for multipotential differentiation is considered.