The first step in diagnosing pheochromocytoma is usually a series of blood tests and/or urine tests to determine if there is an excess of adrenaline hormones in the body. These tests include:

• 24-hour urine testing for catecholamines (a group of hormones produced by the adrenal glands near the kidneys) and their byproducts (metanephrines). The body rids itself of hormones like adrenaline through the urine. Measuring the levels of these substances in the patient’s urine over a 24-hour period (through repeated testing) can determine if the body is producing too much adrenaline. The test can also measure levels of hormone byproducts (substances that are left behind when the hormone is processed by the liver). Because hormone compounds and byproducts are most concentrated in urine, this test is more accurate than blood testing alone in diagnosing pheochromocytoma.
  
  
• Serum blood testing for catecholamines (including metanephrines). The blood test is the fastest detection method available and will usually be one of the first steps in diagnosing pheochromocytoma. However, hormone levels vary greatly and a blood test may only provide a “snapshot” of the body’s hormone levels. Repeat testing and urine testing help clarify the levels.

If a pheochromocytoma is confirmed, the physician will locate the tumor. About 90 percent of tumors are located in the adrenal glands, but they may also be located elsewhere in the abdomen or in the chest or neck. Pheochromocytomas may appear singly or in groups. Tests used to located tumors include:

• CAT (computed axial tomography) scan. A painless type of x-ray that uses a computer to produce detailed cross-sectional images, or “slices,” of parts of the body. Of all imaging tests that are currently available, the CAT scan is best able to produce images of bone, blood and soft tissues. It is the most common and most accurate test available for diagnosing pheochromocytoma and can also give precise measurements (e.g., size and position of tumor) that will assist the physician in treating this disease.
  
  
• MRI (magnetic resonance imaging). A safe and painless test that produces very clear cross-sectional or three-dimensional images of the body’s tissues, even through bone and other obstructions. An MRI works by placing the patient in a chamber surrounded by a magnetic field. The center (nucleus) of every cell of the patient’s body responds to the magnetic force in characteristic ways, allowing a computer to produce the images. It is similar to the CAT scan in terms of accuracy and the type of information it provides. In addition, MRI testing may give a clearer indication of whether the tumor is malignant (cancerous) or benign. However, a biopsy to confirm the tumor type is usually performed.
  
  
• MIBG scintiscan (or adrenal medullary imaging). A radionuclide-imaging test for diagnosing adrenal tumors that is used if the CAT scan or MRI are negative, but the urine and blood tests remain positive for pheochromocytoma. The test is named for the chemical used during the scan (iodine-131–meta-iodobenzylguanidine, MIBG). Radionuclide imaging is a technique in which tiny amounts of radioactive materials (called “tracers”) are introduced into the patient’s body. The tracers emit a certain type of energy called gamma rays, which are detected by special machines. For the MIBG scan, the tracers are attached to substances that the adrenal glands need to produce adrenaline. After they are injected into the body, the tracers will be concentrated in the adrenal glands, making them visible to the special cameras used during the scan.

Finally, the physician will determine if the tumor is cancerous or benign. If cancerous, the physician will find out what stage the malignant tumor has reached. Tests used for this purpose include:

• PET scan (positron emission tomography). This is a form of nuclear imaging that can measure the metabolic rate of organs. It can be helpful in detecting tumors because they operate at a different metabolic rate than the surrounding organ tissue.
  
  
• Biopsy. The surgical removal of a small piece of the tumor for analysis. A biopsy is the best method for determining if a tumor is benign or malignant. The procedure is usually performed under general anesthesia.

Stages of malignant pheochromocytoma are as follows:

• Localized pheochromocytoma. The tumor is present in only one area of the body and has not spread to other tissue.
  
  
• Regional pheochromocytoma. The cancer has spread beyond its original area, usually into the lymph nodes or tissue surrounding the original tumor. Lymph nodes are small structures found throughout the body that produce and store infection–fighting cells.
  
  
• Metastatic pheochromocytoma. The cancer has spread beyond the lymph nodes and tissue immediately surrounding the original tumor into other areas of the body.
  
  
• Recurrent pheochromocytoma. The cancer has returned after being successfully treated in the past. It may occur in the same location as the original pheochromocytoma or in other areas of the body. Recurrent pheochromocytoma is rare.