A pheochromocytoma is a rare tumor that grows in the adrenal glands, the small hormone-producing organs sitting on top of your kidneys. These tumors develop from specialized cells called chromaffin cells in the inner part of the adrenal gland (the adrenal medulla), and they cause problems by pumping out massive amounts of stress hormones, primarily adrenaline (epinephrine) and noradrenaline (norepinephrine). The result is dramatic surges in blood pressure, a racing heart, and other symptoms that can mimic a panic attack or heart emergency.
How the Tumor Causes Symptoms
Your adrenal glands normally release adrenaline and noradrenaline in carefully controlled amounts during stressful situations. A pheochromocytoma bypasses that control. The tumor independently produces and releases these hormones in unpredictable bursts, flooding your bloodstream with chemicals that spike blood pressure, accelerate your heart rate, and trigger your body’s fight-or-flight response at random or inappropriate times.
About half of pheochromocytomas primarily secrete epinephrine along with varying levels of norepinephrine. Others produce mostly norepinephrine with dopamine as a byproduct. The specific hormone mix can influence which symptoms are most prominent. Epinephrine-dominant tumors tend to cause more palpitations and anxiety, while norepinephrine-dominant tumors more commonly drive sustained high blood pressure.
What It Feels Like
The textbook description is a classic triad: headaches, sweating, and palpitations occurring in sudden episodes. In practice, though, only about 17% of patients actually show up with all three symptoms together, based on a study of 94 cases. Many people experience one or two of these, or present with less obvious signs like anxiety, tremor, nausea, abdominal pain, or unexplained weight loss.
Symptoms often come in episodes lasting minutes to hours, sometimes triggered by physical exertion, certain foods, or even pressure on the abdomen. Between episodes, some people feel completely fine. Others have persistently elevated blood pressure that doesn’t respond well to standard medications. A significant number of pheochromocytomas are now discovered incidentally, meaning they show up on imaging done for an unrelated reason before the patient ever notices classic symptoms.
Pheochromocytoma vs. Paraganglioma
If the tumor grows inside the adrenal gland, it’s called a pheochromocytoma. If the same type of tumor develops outside the adrenal gland, in clusters of nerve-related tissue scattered throughout the body, it’s classified as a paraganglioma. These extra-adrenal tumors can appear along the spine, near the aorta, in the head and neck region (such as near the carotid artery or middle ear), and rarely in locations like the bladder, chest, or even the prostate. Both tumor types originate from the same embryonic nerve tissue, but the distinction matters because paragangliomas carry different risks for malignancy and may require different follow-up.
Who Gets It and Why
Pheochromocytomas are rare. An older teaching framework called the “rule of 10s” estimated that roughly 10% are malignant, 10% bilateral (in both adrenal glands), 10% extra-adrenal, and 10% familial. While this rule provides a rough starting point, the genetic picture has turned out to be much bigger than originally thought. Current estimates suggest about 40% of patients carry a hereditary gene mutation linked to these tumors.
Several genetic syndromes increase risk. These include mutations in genes involved in cell growth signaling and oxygen sensing. The most well-known are VHL (associated with von Hippel-Lindau disease), RET (associated with multiple endocrine neoplasia), NF1 (neurofibromatosis), and several genes in the SDH family (linked to hereditary paraganglioma syndromes). Because the hereditary component is so much larger than once believed, genetic testing is now commonly recommended for anyone diagnosed with a pheochromocytoma or paraganglioma, regardless of family history.
How It’s Diagnosed
The first step is a blood or urine test that measures metanephrines, which are breakdown products of adrenaline and noradrenaline. These tests are highly accurate. Plasma free metanephrines (a blood draw) have a sensitivity of 96% to 100%, meaning they catch nearly every tumor. Urinary metanephrines collected over 24 hours perform similarly, with sensitivity around 97% and specificity around 98%. A normal result on these tests makes a pheochromocytoma very unlikely.
Once biochemistry confirms excess hormone production, imaging pinpoints the tumor’s location. CT scans detect adrenal tumors as small as 0.5 cm with 93% to 100% sensitivity. MRI performs slightly better in some cases. However, both CT and MRI can have specificity as low as 50%, meaning they sometimes flag masses that turn out not to be pheochromocytomas. When the tumor isn’t clearly visible on standard imaging, or when doctors suspect extra-adrenal or metastatic disease, functional imaging comes in. A specialized nuclear scan called MIBG scintigraphy detects about 85% to 88% of adrenal pheochromocytomas, though it performs less well for extra-adrenal tumors. Newer PET-based scans are increasingly preferred and tend to outperform MIBG, particularly for hereditary or metastatic cases.
Treatment: Preparation and Surgery
Surgery to remove the tumor is the primary treatment. But operating on a pheochromocytoma without preparation is dangerous because handling the tumor can trigger a massive hormone release, causing a life-threatening blood pressure crisis on the operating table. To prevent this, patients take blood pressure medications for 10 to 14 days before surgery to block the effects of the excess hormones and allow the body’s blood volume to normalize.
The sequence of these medications matters. An alpha-blocker is always started first. Beta-blockers, which slow the heart rate, are only added after the alpha-blocker is well established. Starting a beta-blocker first can paradoxically worsen blood pressure by leaving certain hormone receptors unopposed. Most tumors are now removed laparoscopically (through small incisions), and for patients with a single benign tumor, surgery is often curative.
Is It Cancer?
Determining whether a pheochromocytoma is malignant isn’t straightforward. Unlike many other tumors, pathologists cannot reliably distinguish benign from malignant pheochromocytomas just by looking at the cells under a microscope. The 2022 WHO classification recognizes that all pheochromocytomas carry some metastatic potential. The definitive proof of malignancy is the presence of metastases: tumor spread to locations where chromaffin tissue doesn’t normally exist, such as bone, liver, or lymph nodes. Even this can be complicated in patients with hereditary syndromes, where what looks like metastatic spread might actually be multiple independent primary tumors.
Long-Term Follow-Up
Even after successful surgery, pheochromocytomas can recur years or even decades later. Current guidelines recommend a blood or urine metanephrine test two to six weeks after surgery to confirm the tumor was fully removed. If levels have normalized, annual follow-up with hormone testing and blood pressure monitoring should continue for at least 10 years.
Patients at higher risk for recurrence need lifelong monitoring. This includes people diagnosed at a young age, those with a known genetic mutation, anyone who had a paraganglioma rather than an adrenal tumor, and those whose original tumor was large or multifocal. If hormone levels rise again during follow-up, imaging studies are the next step to look for recurrent or metastatic disease. This long surveillance window reflects the tumor’s unpredictable biology, where a recurrence a decade after initial surgery, while uncommon, is not unheard of.