Pitfalls in the diagnosis of erosive changes in expanding lesions of the pituitary fossa.

Tomographic findings were reviewed in 47 cases of transsphenoidal hypophysectomy for expanding intrasellar mass. Changes caused by factors other than the presence of a mass were classified into five groups. These were: (a) patterns of aeration of the sphenoid sinus, (b) sites of attachment of the sphenoid sinus septum, (c) thickening of the mucous membrane of the sphenoid sinus, (d) extensive thinning of the sellar cortex, and (e) sloping floors. These were the most common sites for causes of error in interpreting expanding lesions. An increased awareness of these pitfalls should decrease interpretive error.