[A case of ectopic pituitary adenoma localized in the sphenoid sinus]

Intrasphenoidal pituitary adenoma is relatively rare. Only 13 cases have been reported in the literature. We present a case of intrasphenoidal pituitary adenoma in a 74-year-old man. He had no endocrinological abnormalities. Skull tomograms revealed sellar floor erosion but showed no enlargement of the pituitary fossa. Computed tomographic (CT) scan revealed an isodense mass showing no contrast enhancement in the sphenoid sinus. The intrasphenoidal tumor appeared slightly hypointense compared with normal brain on T1-weighted image, and showed less contrast enhancement after intravenous injection of Gd-DTPA on magnetic resonance imaging (MRI). Transsphenoidal pituitary microsurgery was performed, and all of the intrasphenoidal tumor was removed with the mucosa. The sellar floor was thin and easily breakable in parts. After removal of the sellar floor the dura was opened, but no evidence of a pituitary tumor was shown. No connection between the pituitary gland and the sphenoidal tissue was found. Microscopic examination of sections showed tumor cell nests in the sphenoidal mucosa. We think this ectopic pituitary adenoma occurred through the migration of Rathke's pouch in the sphenoid sinus.