Staging is a way of describing where a tumor is located, if or where it has spread, and whether it is affecting the functions of other organs in the body. Doctors use diagnostic tests to determine the tumor’s stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a patient’s prognosis (chance of recovery). There are different stage descriptions for different types of tumors. 

Because a pituitary gland tumor is most commonly noncancerous and called a pituitary adenoma, it is usually classified according to its size on an MRI (see Diagnosis [2]).

• A microadenoma is small (10 millimeters [mm] or less).
• A macroadenoma is larger and can extend outside the sella turcica (the bony structure around the pituitary gland). A macroadenoma is larger than 10 mm at its widest point.

Other factors considered when classifying a pituitary gland tumor include whether the tumor is functional (meaning, what, if any, hormone(s) it makes) and whether it has grown into nearby structures (most commonly, the cavernous sinus, an area near the pituitary gland that contains the carotid artery and several important nerves that control eye movement).