The occurrence of a pituitary adenoma located entirely outside the sella turcica, so-called ectopic adenoma, is extremely rare. We report a case of a non secreting-pituitary adenoma located above the diaphragma sellae, with no invasion into the sella turcica, confirmed at surgery. The tumor was initially treated unsuccessfully by operations via the transphenoidal route. After initial negative exploration by the transphenoidal route, the patient was successfully treated by an endoscopic endonasal transphenoidal approach extended to the tuberculum sellae and the posterior planum sphenoidale to access the suprasellar supraglandular region. A brief review of ectopic adenomas and a discussion of the preoperative diagnosis are presented.