Pheochromocytoma is extremely rare, affecting roughly 2 to 8 people per million each year. To put that in perspective, in a city of one million residents, fewer than 10 would be diagnosed in a given year. Despite its rarity in the general population, the tumor shows up more often in certain groups, particularly people being evaluated for hard-to-control blood pressure or those with a family history of specific genetic conditions.
How Common Is It in the General Population?
Pheochromocytoma is a tumor that grows in the adrenal glands, the small hormone-producing organs that sit on top of your kidneys. These tumors produce excess adrenaline and related stress hormones, which can cause dramatic spikes in blood pressure, a racing heart, headaches, and heavy sweating. The annual incidence of 2 to 8 per million makes it one of the rarer causes of high blood pressure, accounting for only 0.1 to 0.6% of all people with hypertension.
Most people diagnosed are between 30 and 50 years old, though the tumor can appear at any age. About 10 to 13% of cases occur in children. Related tumors called paragangliomas, which grow outside the adrenal glands in nerve tissue along the spine or near major blood vessels, are even less common, occurring at roughly 10 to 15% the rate of adrenal pheochromocytomas.
Many Cases Go Undetected
One of the striking features of pheochromocytoma is how often it escapes diagnosis during a person’s lifetime. Historically, a significant number of cases were only discovered at autopsy. Studies from the mid-20th century found that 36 to 42% of all pheochromocytoma cases were first identified after death. A Swedish study covering 1958 to 1981 reported that nearly 42% of patients were diagnosed postmortem.
That picture has changed dramatically with modern imaging. A Danish study covering 2007 to 2015 found zero cases diagnosed at autopsy, while a Canadian study from 2012 to 2019 reported less than 1%. The shift comes from the widespread use of CT scans and MRIs for unrelated health issues. Today, the majority of pheochromocytomas are found incidentally, meaning they show up on a scan done for another reason. In recent data, over half of cases were discovered this way. About 7% of all adrenal masses found incidentally on imaging turn out to be pheochromocytomas. The typical tumor measures 4 to 5 cm at the time of discovery.
Higher Prevalence in Certain Groups
While the tumor is rare overall, it clusters in specific populations. Among people with an adrenal mass found by chance on imaging, about 5% will have a pheochromocytoma. Among people with resistant hypertension, the numbers are lower (0.1 to 0.6%) but still high enough that doctors routinely screen for it when blood pressure doesn’t respond to standard treatment.
The strongest risk factor is genetics. Older medical teaching estimated that only 10% of cases were hereditary, but current data has tripled that figure. Roughly 40% of all pheochromocytomas can now be traced to an inherited gene mutation. More than 15 different genes have been linked to the condition, but the most common culprits involve a group of genes that affect how cells produce energy (the succinate dehydrogenase family). Other well-known genetic syndromes associated with these tumors include multiple endocrine neoplasia type 2, von Hippel-Lindau disease, and neurofibromatosis type 1. If you have a first-degree relative with pheochromocytoma, genetic testing is a standard part of evaluation.
The “Rule of Tens” Is Outdated
For decades, medical students learned the “rule of tens” for pheochromocytoma: 10% are malignant, 10% occur outside the adrenal glands, 10% are hereditary, and 10% occur in children. Nearly every one of those figures has been revised upward with better data and genetic testing.
The hereditary proportion is now closer to 40%. The metastatic rate is estimated at about 17%, not 10%. And pediatric cases account for 10 to 13% of diagnoses, with children more likely than adults to have bilateral tumors (in both adrenal glands) and a hereditary cause. The World Health Organization acknowledged these shifts in its 2022 classification by eliminating the distinction between “benign” and “malignant” pheochromocytoma entirely. All of these tumors are now considered to have metastatic potential, because some patients develop spread 20 or more years after the original tumor is removed.
What Metastatic Potential Means
About 17% of pheochromocytomas and paragangliomas eventually spread to distant sites like bone, liver, lungs, or lymph nodes. There is currently no reliable way to predict which tumors will metastasize based on how they look under a microscope. The only definitive sign of metastatic disease is actually finding tumor cells in locations where the tissue doesn’t normally exist.
This is why long-term follow-up matters even after successful surgery. A tumor that appeared completely contained at the time of removal can, in rare cases, show signs of spread years or even decades later. The reclassification by the WHO reflects this reality: rarity doesn’t mean the tumor can be dismissed after treatment.
Putting the Numbers Together
Pheochromocytoma sits in an unusual space among rare diseases. It is genuinely uncommon, with only a handful of cases per million people per year. But it is far less rare than it once appeared, largely because better imaging catches tumors that previously went undiagnosed until autopsy. The genetic contribution is also much larger than historically taught, meaning that a single diagnosis in a family can prompt screening that uncovers additional cases. For the average person, the odds of having a pheochromocytoma are vanishingly small. For someone with unexplained episodic high blood pressure, an adrenal mass on a scan, or a family member with the condition, those odds shift enough to warrant specific testing.