Astroblastoma: electron microscopy and immunohistochemical findings: case report. The clinical, histological, immunohistochemical, and electron microscopic features of a cerebral astroblastoma are reported. The patient is a young woman with a superficial parietal tumor. Macroscopic findings include a well-delineated superficial nodule with a hard central core. Histological study disclosed a predominantly papillary tumor with hyalinized vessels. Tumor cells were scarcely positive with immunohistochemical stain for glial fibrillary acidic protein, extensive and diffusely positive with vimentin and neuron-specific enolase, and intensely positive with S-100 and epithelial membrane antigen in the papillary areas. Ultrastructural study showed abundant intermediate filaments forming bundles in tumoral cytoplasms, membrane junctions, and external laminae when cells were in contact with collagen fibers. Based on immunohistochemical and ultrastructural characteristics, we believe that the filaments seen in tumor cells are mainly vimentin filaments. These peculiar immunohistochemical patterns in a glioma may aid in the histological diagnosis of this rare tumor type. 