[A case of neuroaxis endodermal cyst].

The patient was a 69-year-old male. During examination of possible deafness, a cystic mass was found in the left frontal lobe, which required surgical intervention. Though the mass adhered strongly to the dura mater macroscopically, the boundary between the mass and arachnoid was clear, having a meningioma-like appearance. The pathological diagnosis was epithelial cyst consisting of layered cubic to cylindrical epithelium. It is essential to perform an electronmicroscopic or immunohistological examination for knowing the origin of an epithelial cyst in the neuroaxis, that is, of ectodermal, endodermal, or mesenchymal origin. However, the diagnosis of heterotopic endodermal cyst was established in this patient because the continuity with ependyma cells or choroid plexus was absent without the so-called ectodermogenic tissue such as glia and nerve cells.