Pituitary Gland Tumor: Diagnosis

Approved by the Cancer.Net Editorial Board, 10/2022

ON THIS PAGE: You will find a list of common tests, procedures, and scans that doctors use to find the cause of a medical problem. Use the menu to see other pages.

Doctors use many tests to find, or diagnose, a tumor and learn if it is cancerous. They also do tests to learn if cancer has spread to another part of the body from where it started. If the cancer has spread, it is called metastasis. Doctors may also do tests to learn which treatments could work best.

For most types of tumors, a biopsy is the only sure way for the doctor to know what type it is. In a biopsy, the doctor takes a small sample of tissue for testing in a laboratory. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis.

How a pituitary gland tumor is diagnosed

There are many tests used for diagnosing a pituitary gland tumor. Not all tests described here will be used for every person. Your doctor may consider these factors when choosing a diagnostic test:

  • The type of a tumor suspected

  • Your signs and symptoms

  • Your age and general health

  • The results of earlier medical tests

In addition to a physical examination, the following tests may be used to diagnose a pituitary gland tumor.

  • Neurological examination. An evaluation of the central nervous system that may include testing a person’s reflexes, motor and sensory skills, balance and coordination, and mental status.

  • Laboratory tests. A blood test may be recommended so the doctor can measure the amounts of certain hormones in the blood. These tests may need to be repeated several times so the doctor can understand how hormones are produced over time, or to confirm that hormone levels are consistently abnormal. Sometimes a person may be given a drug or hormone before the blood measurements are done; this is called provocative testing.

    If Cushing's disease, which is described in Signs and Symptoms, is suspected, samples of saliva may be collected as well as one or more 24-hour urine samples. That means all urine produced in a 24-hour period is saved and sent for analysis of cortisol levels. If acromegaly is suspected, a diagnosis can be confirmed by a measurement of serum GH and IGF-1 levels. Prolactin-producing tumors are confirmed by measurement of the serum prolactin level. TSH-producing tumors are recognized using thyroid function tests.

  • Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. MRI can be used to measure the tumor’s size. A special dye called gadolinium is given before the scan to create a clearer picture. This dye can be injected into a patient’s vein or given as a pill or liquid to swallow. MRI is better than a computed tomography scan, which is described below, to diagnose most pituitary gland tumors. As a result, MRI is now the standard diagnostic test.

  • Computed tomography (CT or CAT) scan. A CT scan takes pictures of the inside of the body using x-rays taken from different angles. A computer combines these images into a detailed 3-dimensional image that shows any abnormalities or tumors. A CT scan can be used to measure the tumor’s size. Sometimes, a special dye called a contrast medium is given before the scan to provide better detail on the image. This dye can be injected into a patient’s vein or given as a pill or liquid to swallow.

    A CT scan is usually used only for patients who have a pacemaker or an aneurysm clip, which may prevent them from having an MRI, which is described above.

  • Visual field exam. There are optic nerves above the pituitary gland. A large pituitary gland tumor may press on those nearby nerves. In this test, the patient is asked to find points of light on a screen, using each eye separately. The most common visual field problem caused by a pituitary gland tumor is loss of the ability to see objects along the edge of the person’s field of vision.

    It is important to remember that other diseases can also cause vision loss. That is why it is important for the doctor to consider all possible causes carefully before coming to a conclusion about the reason for a vision problem.

  • Biopsy. A biopsy is the removal of a small amount of tissue for examination under a microscope. Other tests can suggest that a tumor is present, but only a biopsy can make a definite diagnosis. The sample removed during the biopsy is analyzed by a pathologist. A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease.

    The biopsy is usually done as part of the surgery to remove the pituitary tumor (see Types of Treatment). A tissue sample from the pituitary gland tumor should be checked by the pathologist for production of each of the hormones mentioned in the Introduction section, with the exception of lipotropin and melanocyte stimulating hormone, to correctly classify the tumor. Biopsies can also determine the type of cells composing the tumor, even if they are not secreting hormones in excess. Then, the pathologist can make some reasonable estimates about the potential growth or aggressiveness of this type of tumor.

  • Lumbar puncture (spinal tap). A lumbar puncture is a procedure in which a needle is used to take a sample of cerebrospinal fluid (CSF) to look for tumor cells, blood, or tumor markers. Tumor markers are substances found in higher than normal amounts in the blood, urine, or body tissues of people with certain kinds of tumors. CSF is the fluid that flows around the brain and the spinal cord. Doctors generally give an anesthetic to numb the lower back before the procedure. This test is only rarely needed to help diagnose a pituitary abnormality.

After diagnostic tests are done, your doctor will review the results with you. If the diagnosis is a tumor, these results also help the doctor describe the tumor; this is called staging.

The next section in this guide is Stages. It explains the system doctors use to describe the extent of the disease. Use the menu to choose a different section to read in this guide.