[Epithelial cyst occurring on the anterior surface of the brain stem--case report and review of the literatures].

Epithelial cysts in the posterior fossa are very rare, and only 22 cases have been reported in literatures. We report a case of epithelial cyst occurring on the anterior surface of the brain stem. A 31-year-old man was admitted to our hospital complaining of right hemiparesis and dysarthria. Plain CT showed a heterogeneous (isodense-hyperdense) mass in front of the pons, and was not enhanced after injection of contrast medium. As for findings of MRI, the tumor revealed as heterogeneous (isointense-hyperintense) mass on T1-weighted image and also heterogeneous (hypointense-hyperintense) mass on T2-weighted image. We removed partially the tumor which content was like yogurt. The histological findings of the cyst wall revealed a pseudostratified columnar ciliated epithelium.