Diagnosing pheochromocytoma requires a careful combination of laboratory testing and advanced imaging techniques to locate these rare adrenal tumors and assess their hormone production, enabling doctors to plan the safest and most effective treatment approach.

Who Should Undergo Diagnostics and When to Seek Medical Evaluation

People who experience certain patterns of symptoms should consider seeking medical evaluation for pheochromocytoma. The most common reason to pursue diagnostic testing is the presence of high blood pressure, particularly when it is difficult to control with medications or occurs in younger adults without typical risk factors for hypertension.^[1] High blood pressure associated with pheochromocytoma can behave in unusual ways, sometimes staying elevated continuously or spiking dramatically in episodes that come and go unpredictably.^[1]

Individuals experiencing a classic triad of symptoms—severe headaches, excessive sweating, and rapid or pounding heartbeat—should discuss these concerns with their healthcare provider.^[2] These symptoms often occur together in brief episodes or spells lasting 15 to 20 minutes, though they can happen several times a day or less frequently.^[6] Between these episodes, some people feel relatively normal, while others continue to experience symptoms.^[6]

Anyone with a family history of pheochromocytoma or related tumors called paragangliomas should inform their doctor, as approximately 30 to 40 percent of these tumors are hereditary.^[6] People diagnosed with certain inherited conditions also have increased risk and may benefit from regular screening even without symptoms. These conditions include multiple endocrine neoplasia type 2 (MEN2), von Hippel-Lindau disease (VHL), and neurofibromatosis type 1 (NF1).^[3]

Sometimes pheochromocytomas are discovered accidentally when imaging scans are performed for completely unrelated reasons.^[3] These incidental findings require follow-up testing to determine whether the discovered mass is a pheochromocytoma and whether it is producing excess hormones. It is worth noting that some people with pheochromocytomas do not experience any symptoms at all, which is why these tumors can sometimes go undiagnosed for extended periods.^[2]

Classic Diagnostic Methods to Identify the Disease

Diagnosing pheochromocytoma typically begins with laboratory tests that measure hormone levels in blood or urine. These tests look for elevated amounts of catecholamines—a group of hormones that includes epinephrine (adrenaline) and norepinephrine (noradrenaline)—or their breakdown products called metanephrines.^[11] When a pheochromocytoma is present, these substances are usually found at much higher levels than normal because the tumor continuously or intermittently releases them into the bloodstream.^[3]

Laboratory Testing: The Foundation of Diagnosis

The 24-hour urine test is one standard approach to diagnosis. With this method, patients collect every urine sample they produce over a full 24-hour period. The collected samples are then analyzed in a laboratory to measure the total amount of catecholamines and metanephrines excreted during that day.^[11] This test provides a comprehensive picture of hormone production over time rather than just a single moment, which can be helpful since hormone release from pheochromocytomas can vary throughout the day.^[1]

Blood tests offer another way to detect excess catecholamines and metanephrines. A healthcare professional draws a blood sample that is sent to a laboratory for analysis.^[11] Elevated levels of metanephrines in blood are particularly suggestive of pheochromocytoma, as these breakdown products remain in circulation longer than the hormones themselves.^[11] Some medications and foods can interfere with test results, so patients may be asked to avoid certain substances or to fast before testing.^[11]

It is important to understand that preparing properly for these tests matters significantly. Doctors may ask patients to temporarily stop taking certain medications, avoid caffeine, or refrain from eating for a period before the test.^[11] Patients should never stop taking prescribed medications without explicit instructions from their healthcare team, as this could be dangerous. Written directions about how to collect, store, label, and return samples should be followed carefully to ensure accurate results.^[11]

Imaging Studies: Locating the Tumor

Once laboratory tests suggest the presence of a pheochromocytoma, imaging studies become essential to locate the tumor and determine its size and characteristics. Several different imaging technologies may be used, each with particular strengths.^[11]

A CT scan (computed tomography) combines multiple X-ray images taken from different angles to create detailed cross-sectional pictures of the body. This technology is particularly good at showing the structure of the adrenal glands and can reveal tumors as small as a few millimeters.^[11] CT scans are commonly used as a first imaging step because they provide excellent anatomical detail and are widely available in most medical centers.

An MRI scan (magnetic resonance imaging) uses powerful magnets and radio waves instead of radiation to create detailed images of soft tissues. MRI can be particularly helpful in distinguishing pheochromocytomas from other types of adrenal masses.^[11] On certain types of MRI sequences, pheochromocytomas often appear very bright, which can help confirm the diagnosis.

Specialized nuclear medicine scans provide another diagnostic option. MIBG imaging (metaiodobenzylguanidine) involves injecting a small amount of radioactive material that is specifically taken up by pheochromocytoma cells.^[11] A special camera then detects where this material has accumulated in the body, highlighting the location of tumors. This technique is particularly useful for finding tumors outside the adrenal glands or for detecting multiple tumors.^[11]

PET scans (positron emission tomography) work on a similar principle, using different radioactive compounds that concentrate in pheochromocytoma tissue.^[11] PET imaging can be especially valuable when other scans have not clearly identified a tumor location or when doctors need to check whether cancer has spread to other parts of the body.

Additional Diagnostic Considerations

Distinguishing pheochromocytoma from other conditions that cause similar symptoms is an important part of diagnosis. Panic attacks, for example, can produce symptoms that overlap significantly with those of pheochromocytoma, including rapid heartbeat, sweating, trembling, and a sense of impending doom.^[2] Other conditions like thyroid disorders, heart rhythm problems, and even certain psychiatric medications can also mimic pheochromocytoma symptoms. The laboratory and imaging tests help doctors differentiate between these possibilities.

For patients with confirmed or suspected pheochromocytoma, genetic testing and counseling are recommended as part of the diagnostic workup.^[8] Since a significant proportion of these tumors are associated with inherited genetic mutations, identifying such mutations can have important implications not only for the patient’s treatment but also for family members who might be at risk.^[6]

Diagnostics for Clinical Trial Qualification

Patients who are considering participation in clinical trials for pheochromocytoma treatment may need to undergo additional or more frequent diagnostic testing as part of the enrollment process. Clinical trials use standardized criteria to ensure that all participants have similar disease characteristics, which allows researchers to accurately evaluate whether experimental treatments are working.

Baseline measurements of catecholamine and metanephrine levels are typically required before a patient can enroll in a clinical trial.^[13] These tests establish the severity of hormone overproduction and provide a reference point for measuring whether treatment reduces hormone levels. Trial protocols often specify exactly which laboratory tests must be performed, which laboratory methods should be used, and how recently the tests must have been completed.

Imaging studies performed for clinical trial purposes may follow specific protocols that differ slightly from routine clinical imaging. For example, trials might require that scans be performed using particular settings or techniques to ensure consistency across all study sites. Measurements of tumor size taken from these scans help determine eligibility and provide baseline data for tracking whether tumors shrink, grow, or remain stable during treatment.^[13]

Some clinical trials focus specifically on malignant or metastatic pheochromocytomas—cases where the tumor has spread beyond the adrenal glands to other parts of the body.^[13] Qualifying for these trials typically requires imaging evidence showing the extent and location of disease spread. Additional biopsies may sometimes be needed to confirm that distant tumors are indeed pheochromocytoma cells rather than another type of cancer.

Functional imaging with specialized nuclear medicine scans may be particularly important for clinical trial enrollment. Some experimental treatments are designed to work only in tumors that take up specific radioactive tracers, so demonstrating uptake on a screening scan may be necessary before a patient can receive the treatment.^[13]

Before enrolling in any clinical trial, patients undergo a thorough screening process that may include a complete physical examination, review of medical history, assessment of overall health status, and sometimes heart function testing.^[13] These evaluations help ensure that participation in the trial is safe and appropriate for each individual patient. The specific diagnostic requirements vary depending on the trial design and the treatment being studied, so patients interested in clinical trials should discuss qualification criteria in detail with the research team.