Transsphenoidal surgery is a procedure used to remove pituitary tumors from the brain. The surgeon works through a small opening (ostium) at the back of the nose (septum) that leads to an air pocket called the sphenoid sinus. To access the pituitary tumor, the surgeon goes through the sphenoid sinus and cuts through the tissue covering the pituitary gland. The tumor is removed with small instruments called curets. A small scope inserted through the sphenoid sinus helps the surgeon to visualize the tumor. A large tumor may need to be cut into smaller pieces before it's removed.