A pheochromocytoma is a rare, usually non-cancerous tumor that develops in the chromaffin cells located in the center of the adrenal gland. These specialized cells are responsible for producing and releasing powerful hormones called catecholamines, which include adrenaline and noradrenaline. In the United Kingdom, healthcare professionals recognize this condition as a significant cause of secondary hypertension because the tumor can release these hormones in sudden, large bursts. This “hormonal flooding” triggers the body’s fight or flight response at inappropriate times, leading to severe physical symptoms and potential cardiovascular strain. Understanding how these tumors form and the biological mechanisms that drive their growth is essential for ensuring a safe diagnostic pathway and effective surgical intervention.
What We’ll Discuss in This Article
- The biological origin of pheochromocytoma in the adrenal medulla.
- The role of chromaffin cells in hormone production and release.
- The genetic and environmental factors that trigger tumor formation.
- How the “Rule of Tens” helps clinicians categorize these tumors.
- The impact of excess adrenaline on the heart and blood pressure.
- Diagnostic procedures used in the UK to detect catecholamine excess.
The origin of pheochromocytoma in the adrenal medulla
The adrenal glands are composed of two distinct parts: the outer cortex and the inner medulla. A pheochromocytoma specifically forms in the medulla, which is the part of the gland that functions as part of the sympathetic nervous system. The medulla is made up of chromaffin cells, which are derived from the same embryonic tissue as nerve cells. In a healthy person, these cells store adrenaline and release it only when the brain signals that the body is under stress. When a pheochromocytoma develops, a cluster of these chromaffin cells begins to multiply uncontrollably, forming a tumor. Because these are “functional” tumors, they do not just take up space; they actively manufacture and store massive quantities of adrenaline and noradrenaline, often far beyond what the body would ever naturally require.
regardless of whether they are cancerous or not.
Genetic factors and hereditary syndromes
While many pheochromocytomas occur sporadically without a clear cause, a significant portion estimated at 30 to 40 percent is linked to inherited genetic mutations. In the United Kingdom, patients diagnosed with this tumor are often offered genetic testing to see if they have an underlying syndrome. Common genetic triggers include:
- Multiple Endocrine Neoplasia type 2 (MEN2): A condition that causes tumors in various endocrine glands.
- Von Hippel-Lindau (VHL) disease: A disorder that leads to the growth of tumors and cysts throughout the body.
- Neurofibromatosis type 1 (NF1): A condition characterized by tumors on the nerve tissue and skin.
- Hereditary Paraganglioma-Pheochromocytoma Syndromes: Mutations in the succinate dehydrogenase (SDH) genes that specifically predispose individuals to these types of tumors.
Identifying a genetic cause is vital because it determines whether the patient needs long-term screening for other tumors and whether their family members should also be tested.
The clinical “Rule of Tens”
Medical professionals in the UK often refer to the “Rule of Tens” when describing the characteristics of pheochromocytomas, although modern data suggests these percentages are slightly shifting. Traditionally, this rule states that:
- 10 percent are malignant: The majority of these tumors are benign and do not spread.
- 10 percent are bilateral: Meaning they occur in both adrenal glands simultaneously.
- 10 percent are extra-adrenal: These form outside the adrenal glands in similar nerve tissues and are called paragangliomas.
- 10 percent are discovered incidentally: Often found during scans for unrelated abdominal issues.
While these figures are approximations, they help clinicians understand the diverse ways these tumors can present and guide the search for tumors elsewhere in the body if one is discovered.
Impact of catecholamine excess on the body
The defining characteristic of a pheochromocytoma is the sudden release of adrenaline and noradrenaline, which causes a “paroxysm” or a classic attack. During these episodes, the heart rate spikes, blood pressure rises to dangerous levels, and the patient may experience intense headaches, excessive sweating, and a feeling of impending doom. Over time, the constant or fluctuating high blood pressure can damage the blood vessels and place an enormous strain on the heart muscle, leading to an increased risk of heart attack, stroke, or heart failure. The NICE clinical knowledge summaries highlight that managing this hypertension with specific medications, called alpha-blockers, is a mandatory first step before any surgical attempt to remove the tumor is made.
Diagnostic pathways and biochemical testing
Because pheochromocytomas are rare, they are often diagnosed through specialized biochemical tests rather than standard blood work. The most common test in the UK is the measurement of metanephrines, which are the breakdown products of adrenaline and noradrenaline. These can be measured in a 24-hour urine collection or a specialized blood test called a plasma metanephrine test. If these markers are significantly elevated, it provides strong evidence of a catecholamine-secreting tumor. Following biochemical confirmation, imaging studies such as a CT or MRI scan of the abdomen are used to locate the tumor. In some cases, a specialized nuclear medicine scan, such as an MIBG scan, is used to identify if the tumor has spread or if there are additional tumors elsewhere in the body.
Conclusion
A pheochromocytoma is a functional tumor of the adrenal medulla that forms from the overgrowth of hormone-producing chromaffin cells. Whether occurring sporadically or as part of a genetic syndrome, these tumors cause significant health risks by flooding the body with excess adrenaline and noradrenaline. This leads to severe, episodic high blood pressure and a range of cardiovascular complications. Through precise biochemical testing for metanephrines and careful imaging, UK clinicians can accurately identify these tumors and prepare patients for surgical removal. Achieving hormonal stability through medication is a critical part of the treatment journey. If you experience severe, sudden, or worsening symptoms such as an extremely rapid heart rate, a pounding headache, or severe chest pain, call 999 immediately.
Is a pheochromocytoma a type of cancer?
The vast majority—about 90 percent—of pheochromocytomas are benign (non-cancerous), but they are still considered serious because of the powerful hormones they release.
Can stress cause a pheochromocytoma to form?
No, stress does not cause the tumor to form, but physical stress or certain medications can trigger a tumor that is already present to release a burst of hormones.
Why is surgery for this tumor considered high risk?
Touching or moving the tumor during surgery can cause a massive release of adrenaline, leading to dangerous spikes in blood pressure, which is why patients are prepared with medication for weeks beforehand.
Do I need genetic testing if I have this tumor?
Current UK guidelines recommend that most people diagnosed with a pheochromocytoma should be offered genetic counseling and testing, as a high percentage have an underlying genetic cause.
What is the difference between a pheochromocytoma and a paraganglioma?
A pheochromocytoma is located specifically in the adrenal gland, while a paraganglioma is a similar tumor that forms in nerve tissues elsewhere in the body.
Will my high blood pressure go away after the tumor is removed?
In many cases, blood pressure returns to normal immediately after surgery, although some patients may still have underlying hypertension that requires ongoing management.
Can these tumors come back after surgery?
While rare, there is a small risk of recurrence, especially in patients with genetic syndromes, which is why long-term follow-up with an endocrinologist is required.
Authority Snapshot
This article provides an evidence-based overview of pheochromocytoma and its impact on adrenal function within the UK medical system. It was written by Dr. Rebecca Fernandez and reviewed by Dr. Stefan to ensure total alignment with the latest NHS and NICE clinical guidance. The purpose of this guide is to help patients understand the rare nature of these tumors and the importance of biochemical diagnosis and specialized surgical preparation.
