Abstract
A 54-year-old man presented with a few years history of headache. The patient had no neurological deficit. Neuroimaging studies revealed a nonenhancing, extradural cystic lesion overlying the left frontal convexity. The majority of the lesion seemed to be located in the intradiploic space of the frontal bone. Diffusion-weighted MR imaging showed a homogeneous hypointense mass. We performed a craniotomy and removed the whole tumor along with the entire cyst wall. Histological examination disclosed that the tumor capsule consisted of a layer of pseudostratified ciliated columnar epithelium that stained positive for pankeratin and cytokeratin 7 and negative for GFAP and S-100. Therefore, this tumor was identified as an endodermal cyst. Endodermal cysts are usually found in the spinal canal and an intracranial occurrence of this cyst is exceptional. In addition, the extraaxial, extradural and supratentorial location of this endodermal cyst is extremely rare. We speculate that abnormal embryogenesis during differentiation of the embryonic disc may have played a key role in the pathogenesis of this case.
