Symptomatic suprasellar endodermal cyst, possibly originating from the Seessel's pouch, containing fluid with a high carcinoembryonic antigen level.

A 32-year-old man presented with a rapidly progressive decrease in visual acuity and diplopia. Magnetic resonance imaging (MRI) revealed a suprasellar cystic mass extending to the upper part of the clivus. The content of this cyst showed a slightly higher signal intensity than that of his cerebrospinal fluid (CSF) on T1-weighted images. The cyst stretched the pituitary stalk, but a normal pituitary signal was observed. The cyst wall was maximally resected under neuroendoscopy, which yielded fluid contents that were white and mucous like, with a carcinoembryonic antigen (CEA) level 1,400 ng/ml or higher. On light microscopy, one to two layers of epithelial cells with cylindrical nuclei on loose connective tissue lined the cyst cavity. These cells were positive for periodic acid-Schiff, CEA, and cytokeratin 7 and negative for cytokeratin 20. On electron microscopy, epithelial cells showed many short microvilli with coating material. The cytoplasm was rich in electron-dense material, and dense intercellular adhesion was observed, but neither goblet cells nor cilia were present. On the basis of MRI features, cytokeratin expression patterns and electron microscopic findings, the patient was considered to have a suprasellar endodermal cyst derived from Seessel's pouch.