Reactive glioma in intracranial sarcoma ('sarcoglioma'). Histology, electron microscopy and immunohistochemistry of two additional cases.

The clinicopathologic features of 2 cases of sarcoglioma are described. This rare type of mixed brain tumor is composed of a central core of sarcoma with peripheral distribution of gliomatous elements with gradual transition from reactive to neoplastic astrocytes. The immunohistochemical features showed a strict positivity to glial fibrillary acidic protein only in glial cells, a positivity to vimentin prevalently in sarcomatous cells, whereas the factor VIII-related antigen was negative in astrocytes as well as in sarcomatous cells. The different origin of two neoplastic components is demonstrated well by an ultrastructural study. The morphological observations together with an adequate clinical setting contribute to separate this specific entity from other mixed brain tumors.