Pheochromocytoma is a rare tumor typically originating in the adrenal glands, small organs above your kidneys. These tumors develop from specialized chromaffin cells, which produce and release hormones like adrenaline (epinephrine) and noradrenaline (norepinephrine). An excessive release of these hormones leads to a range of symptoms. Most pheochromocytomas are benign, not cancerous, and do not spread. However, if left undiagnosed and untreated, the overproduction of hormones can lead to serious health complications, including life-threatening high blood pressure, heart problems, and stroke. Timely diagnosis is crucial due to these risks.
Recognizing the Signs
The symptoms of pheochromocytoma stem from the excessive release of catecholamines, such as adrenaline and noradrenaline, into the bloodstream. These hormones trigger the body’s “fight-or-flight” response, leading to various physical manifestations. While symptoms vary, a classic combination often prompts medical suspicion.
This combination includes headaches, profuse sweating, and heart palpitations. Headaches are often severe and throbbing, while sweating can be excessive and occur without apparent reason. Palpitations are experienced as a pounding, fluttering, or rapidly beating heart.
High blood pressure (hypertension) is another prominent feature, frequently severe and challenging to manage with standard treatments. This hypertension can be sustained or occur in sudden, intense episodes. These episodes may be triggered by physical activity, stress, or certain foods, and can last for minutes to hours. Other associated signs may include pallor, tremors, anxiety, and unexplained weight loss.
Biochemical Testing
Biochemical tests are the primary step in diagnosing pheochromocytoma once symptoms suggest its presence. These tests measure the levels of catecholamines and their breakdown products, called metanephrines, in the body. Elevated levels indicate an overproduction of hormones.
Two main types of biochemical tests are commonly used. One involves collecting urine over a 24-hour period to measure 24-hour urine fractionated metanephrines and catecholamines. This method provides a comprehensive assessment of hormone excretion over an entire day, accounting for the episodic nature of hormone release. Patients are instructed to avoid certain foods, beverages, and medications that can interfere with test results, such as caffeine, alcohol, specific decongestants, and some antidepressants.
Another test is the measurement of plasma free metanephrines, which involves a blood sample. Elevated plasma free metanephrines are a highly accurate indicator. While elevated levels from these tests strongly suggest a pheochromocytoma, they are not definitive and require further investigation.
Imaging Studies
Once biochemical tests indicate a likely pheochromocytoma, imaging studies locate the tumor or tumors. While typically arising in the adrenal glands, about 10% can be found outside, referred to as paragangliomas. Imaging determines the precise location, size, and extent of the tumor, crucial for treatment planning.
Computed tomography (CT) scans are frequently the initial choice due to their wide availability and detailed anatomical views. CT scans can reveal adrenal pheochromocytomas as small as 5-10 mm. Magnetic resonance imaging (MRI) is another valuable tool, particularly when radiation exposure is a concern, such as in pregnant women or children. MRI is also highly sensitive for identifying extra-adrenal tumors and can show characteristic signal intensity patterns.
Specialized nuclear medicine scans, such as MIBG scintigraphy (Metaiodobenzylguanidine scan), are also employed. This scan uses a radioactive tracer absorbed by neuroendocrine cells, including those in pheochromocytomas and paragangliomas. MIBG scintigraphy is particularly useful for detecting tumors outside the adrenal glands or multiple tumors, and can help differentiate pheochromocytomas from other adrenal masses. Other functional imaging techniques, like PET scans, may also be used to further characterize or locate tumors.
Genetic Screening
Genetic screening plays an important role in the diagnosis and management of pheochromocytoma, as a substantial percentage have a hereditary basis. Identifying these genetic factors is important for patient care and assessing family risk.
Genetic testing helps determine if the tumor is part of a familial syndrome. This knowledge guides long-term surveillance, as some genetic conditions predispose individuals to other tumors or health issues. For instance, certain mutations increase the likelihood of developing multiple tumors or recurrent disease.
Several genes are commonly associated with hereditary pheochromocytomas and paragangliomas. These include mutations in the RET gene (linked to Multiple Endocrine Neoplasia type 2 or MEN2), VHL gene (associated with Von Hippel-Lindau syndrome), and NF1 gene (Neurofibromatosis type 1). Additionally, mutations in the SDHB, SDHC, and SDHD genes, part of the succinate dehydrogenase (SDH) complex, are frequently identified. Genetic testing can inform screening for at-risk family members, allowing for early detection and intervention if they carry the mutation.