Several tests may be used to diagnose pituitary tumors, including:

• Physical exam and history 
• CT or CAT (computerized axial tomography) scan This procedure uses a computer connected to an X-ray machine to obtain detailed pictures of areas inside the body. A dye may be used to help visualize organs or tissues more clearly.
• Angiography This procedure allows doctors to get a clearer image of the blood vessels by injecting them with a dye that makes the blood vessels stand out on X-ray film.
• MRI (magnetic resonance imaging) MRI creates a series of detailed pictures of areas inside the body, using the combination of a powerful magnet, radio waves and computer imaging.
• Biopsy Tissue samples are examined under the microscope to determine what types of cells are present.
• Lumbar puncture (spinal tap)  This procedure is used to look for cancer cells in the cerebrospinal fluid. An area  in the lower part of the back is numbed and some of the fluid is withdrawn using  a needle.