70-year-old woman comes to physician complaining of visual loss. Her MRI scan shows an enlarged pituitary gland that lies in sella turcica, immediately posterior and superior to which of the following structures?

Pituitary gland lies in the hypophyseal fossa of sella turcica of sphenoid bone, which lies immediately posterior and superior to sphenoid sinus and medial to cavernous sinus. Frontal sinus lies in the frontal bone. Maxillary sinus lies in the maxilla lateral to lateral wall of nasal cavity. Ethmoid sinus (composed of air cells) lies between orbit and nasal cavity. Mastoid air cells lie in the mastoid process of the temporal bone.