This is a medical question of type : exams and tests 
 How to diagnose Childhood Craniopharyngioma ? 
 Tests that examine the brain, vision, and hormone levels are used to detect (find) childhood craniopharyngiomas. The following tests and procedures may be used:         -   Physical exam and history : An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patients health habits and past illnesses and treatments will also be taken.    -   Neurological exam : A series of questions and tests to check the brain, spinal cord, and nerve function. The exam checks a persons mental status, coordination, and ability to walk normally, and how well the muscles, senses, and reflexes work. This may also be called a neuro exam or a neurologic exam.     -  Visual field exam: An exam to check a persons field of vision (the total area in which objects can be seen). This test measures both central vision (how much a person can see when looking straight ahead) and peripheral vision (how much a person can see in all other directions while staring straight ahead). Any loss of vision may be a sign of a tumor that has damaged or pressed on the parts of the brain that affect eyesight.    -   CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.    -   MRI (magnetic resonance imaging) of the brain and spinal cord with gadolinium : A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the brain. A substance called gadolinium is injected into a vein. The gadolinium collects around the tumor cells so they show up brighter in the picture. This procedure is also called nuclear magnetic resonance imaging (NMRI).    -   Blood chemistry studies : A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease.    -  Blood hormone studies: A procedure in which a blood sample is checked to measure the amounts of certain hormones released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease in the organ or tissue that makes it. For example, the blood may be checked for unusual levels of thyroid-stimulating hormone (TSH) or adrenocorticotropic hormone (ACTH). TSH and ACTH are made by the pituitary gland in the brain.
                    Childhood craniopharyngiomas are diagnosed and may be removed in the same surgery. Doctors may think a mass is a craniopharyngioma based on where it is in the brain and how it looks on a CT scan or MRI. In order to be sure, a sample of tissue is needed.   One of the following types of biopsy procedures may be used to take the sample of tissue:         -  Open biopsy: A hollow needle is inserted through a hole in the skull into the brain.    - Computer-guided needle biopsy: A hollow needle guided by a computer is inserted through a small hole in the skull into the brain.    - Transsphenoidal biopsy: Instruments are inserted through the nose and sphenoid bone (a butterfly-shaped bone at the base of the skull) and into the brain.         A pathologist views the tissue under a microscope to look for tumor cells. If tumor cells are found, as much tumor as safely possible may be removed during the same surgery.   The following laboratory test may be done on the sample of tissue that is removed:         -   Immunohistochemistry : A test that uses antibodies to check for certain antigens in a sample of tissue. The antibody is usually linked to a radioactive substance or a dye that causes the tissue to light up under a microscope. This type of test may be used to tell the difference between different types of cancer.