The patient went on to have a resection. 

Histology

The sections show cyst lining, which comprises a single layer of ciliated flattened to cuboidal epithelium. The epithelial cells show no nuclear atypia. The wall is fibrous. There is some adjacent normal anterior pituitary gland tissue. No evidence of pituitary adenoma or malignancy is seen.

FINAL DIAGNOSIS: Rathke cleft cyst.

Discussion

Although most Rathke's cleft cysts are small and intrapituitary, they can sometimes, like in this case, extend out of the fossa and into the suprasellar cistern.