In this kind of surgery (called "transsphenoidal surgery"), the surgeon makes a small cut deep inside the nose. Then, the surgeon inserts special tools into the "sphenoid sinus," the hollow space below the pituitary gland. That way, the surgeon has access to the pituitary gland and can remove the tumor. In some cases, surgeons do the surgery using a special tool called an "endoscope," which is a long tube with a tiny camera and a light on the end.