Brainstem subarachnoid respiratory epithelial cysts: report of two cases and review of the literature.

Two cystic lesions that were lined by pseudostratified ciliated columnar epithelium containing goblet cells are described. Both lesions were found in the subarachnoid space between the vertebrobasilar arterial system and the brainstem. One cyst was an incidental finding in a patient who died of orbital phycomycosis. The cyst was filled with clear mucinous material. The second cyst presented as a mass adjacent to the brainstem in a woman who had progressive brainstem dysfunction. This lesion showed transition from pseudostratified ciliated columnar epithelium with goblet cells to papillary stratified squamous epithelium, histologic features essentially identical to those of squamous papillomas of the nasal cavity. This lesion was filled with squamous debris. The proposed origin of these lesions is discussed.