Imaging features of a Rathke's cleft cyst further confirmed on histology: 

MICROSCOPIC: The sections show a small fragment of tissue which is covered one surface by a layer of ciliated cuboidal epithelial cells. These show strong immunostaining for cytokeratins CAM5.2 and AE1/AE3. The underlying tissue contains a moderate chronic inflammatory cell infiltrate. No anterior pituitary acini are identified. The features are consistent with the wall and lining of a Rathke's cleft cyst. No evidence of tumor is seen.

DIAGNOSIS: Pituitary cyst wall: Features consistent with wall and lining of Rathke's cleft cyst.