Ultrastructural spectrum of medulloblastoma with immunocytochemical correlations.

Electron microscopy was used to examine 72 cases of medulloblastoma to better characterize the ultrastructural spectrum of this tumor. Twenty-four cases showed prominent neural differentiation. Twenty-three cases showed minimal (21) or no (2) recognizable neural differentiation, and the remainder of the cases (25) showed intermediate differentiation. All 42 cases tested stained for neuron-specific enolase, 28 for synaptophysin, and 12 for neurofilament protein. All cases showed strong reactivity for glial fibrillary acidic protein (GFAP) within reactive astrocytes. Three cases showed reactivity for GFAP within tumor cells. Medulloblastoma exhibits a broad spectrum of neural differentiation, with nearly all cases showing at least some degree of this change, and it universally exhibits participation of reactive astrocytes which can create a potential for diagnostic confusion.