Pheochromocytoma

Pheochromocytoma is a neuroendocrine tumor arising from the chromaffin cells of the adrenal medulla and is characterized by its ability to produce and release variable amounts of catecholamines, particularly norepinephrine and epinephrine, resulting in hemodynamic instability and a broad spectrum of systemic manifestations. Although rare in the general population, it is clinically relevant because it represents a potentially curable cause of secondary hypertension and, when unrecognized, may lead to hypertensive crises, arrhythmias, myocardial ischemia, stroke and severe perioperative events during invasive procedures or anesthesia.

In modern clinical practice, pheochromocytoma is considered together with paragangliomas within the group of chromaffin paraganglionic tumors, while retaining specific characteristics related to its adrenal location, secretory pattern and surgical management. A fundamental concept is that these tumors have a metastatic potential that cannot be reliably predicted by histology alone, and that genetic predisposition is common, with direct implications for family screening, long-term follow-up and the selection of more conservative surgical strategies in selected patients.

Pheochromocytoma is a rare neoplasm, but its clinical epidemiology is strongly influenced by the intensity of diagnostic investigation. An increasing proportion of cases is identified incidentally during abdominal imaging, in parallel with the growing use of CT and MRI for non-endocrine indications. In this setting, clinical observation has shifted from “classic” forms characterized by hypertensive crises and the typical symptom triad toward more heterogeneous presentations, in which catecholamine secretion may be intermittent, mild or masked by cardiovascular therapy.

Pheochromocytoma may occur at any age, but its distribution varies according to the underlying genetic component. In young patients and in multifocal or bilateral cases, the probability of hereditary predisposition is higher, whereas apparently sporadic forms predominate at older ages and are often diagnosed during investigation of an adrenal incidentaloma or resistant hypertension. Sex does not represent a consistent determinant of incidence, although some cohorts show differences related to recruitment setting and the type of genetic variant involved.

A central epidemiological feature is the high prevalence of genetic predisposition among chromaffin tumors. The proportion of patients carrying pathogenic germline variants in predisposing genes is sufficiently high to make genetic evaluation a structural component of management, with implications for identifying multiple tumors, anticipating recurrences and detecting associated paragangliomas. This aspect also changes the concept of a “risk factor,” because in many patients the main determinant is an inherited predisposition rather than a specific environmental exposure.

From a clinical perspective, patient vulnerability largely depends on the cardiovascular response to catecholamines and on organ reserve. Ischemic heart disease, heart failure, pre-existing arrhythmias, cerebrovascular disease and frailty increase the risk of acute complications. Pregnancy is also a high-risk setting because hemodynamic changes and the effects of labor may precipitate catecholaminergic crises, making timely diagnosis essential whenever clinical suspicion is justified.

Finally, an “iatrogenic” epidemiological factor concerns exposure to procedures and medications capable of triggering crises in undiagnosed tumors. Surgery, anesthesia, biopsies, acute stress and certain drugs that interfere with adrenergic regulation or catecholamine release may precipitate critical events. Rather than defining a risk of developing the disease, this observation emphasizes the importance of preoperative identification in patients with adrenal masses or suggestive clinical phenotypes, because preventing perioperative complications is a primary goal of management.

Pheochromocytoma arises from chromaffin cells of the adrenal medulla, which physiologically synthesize catecholamines from tyrosine through an enzymatic pathway involving tyrosine hydroxylase, DOPA decarboxylase, dopamine beta-hydroxylase and, for epinephrine production, phenylethanolamine N-methyltransferase. The adrenal gland integrates preganglionic sympathetic input and converts it into a systemic hormonal output, releasing epinephrine and norepinephrine into the circulation. The tumor disrupts this balance by producing an excessive and often episodic catecholaminergic signal, with widespread hemodynamic and metabolic consequences.

From an etiological perspective, pheochromocytoma may be sporadic or associated with a genetic predisposition. The hereditary component is particularly relevant and is associated with specific phenotypes, including bilateral disease, multifocality and the presence of extra-adrenal paragangliomas. Molecular abnormalities converge on distinct biological programs that influence growth, angiogenesis, cellular metabolism and secretory profile. This explains why some tumors are highly secretory and clinically conspicuous, whereas others produce more subtle signals while still carrying a risk of complications and requiring follow-up.

The pathophysiology is dominated by the effects of catecholamines on adrenergic receptors. Norepinephrine acts predominantly on alpha-adrenergic receptors, causing vasoconstriction and increased peripheral vascular resistance, whereas epinephrine has more balanced effects, including beta-adrenergic actions on heart rate and contractility. The combination of these signals produces a variable hemodynamic profile: sustained hypertension, paroxysmal crises, tachycardia, arrhythmias and, in some circumstances, orthostatic hypotension caused by volume depletion and receptor desensitization. This spectrum explains why blood pressure may fluctuate markedly, with intermittent symptoms and apparently normal periods.

At the cardiovascular level, catecholamines increase myocardial oxygen demand, promote coronary vasospasm and may induce ventricular dysfunction with phenotypes that include catecholamine-induced cardiomyopathy and Takotsubo-like syndromes. Adrenergic overstimulation facilitates supraventricular and ventricular arrhythmias, with increased risk during stress, anesthesia or tumor manipulation. This pathophysiology makes preoperative preparation a crucial phase, because reducing adrenergic instability before surgery substantially lowers intraoperative risk.

Catecholamine secretion also produces metabolic effects. Adrenergic activation promotes glycogenolysis and gluconeogenesis, reduces insulin secretion and increases lipolysis, creating a hyperglycemic and catabolic environment that may manifest as impaired glucose tolerance or diabetes, with possible improvement after tumor resection. Autonomic symptoms such as sweating, tremor, pallor, somatic anxiety and headache are the clinical expression of this systemic hyperactivation and are often the most recognizable signs in paroxysmal forms.

An important modern concept is that pheochromocytoma cannot be classified with certainty as “benign” on histological grounds alone, because metastatic potential exists along a biological continuum. Risk assessment is based on the integration of clinical factors, tumor size, location, genetics and behavior over time. This perspective affects management by supporting prolonged follow-up and an approach that recognizes the disease as potentially chronic, even after apparently complete resection.

The clinical presentation of pheochromocytoma is variable and depends on the amount, pattern and type of catecholamines secreted, as well as on individual sensitivity and cardiovascular reserve. In some forms, presentation is dominated by paroxysmal episodes described by the patient as sudden attacks of malaise with palpitations, tremor, profuse sweating and headache, often associated with marked increases in blood pressure. In other cases, secretion is more continuous and the phenotype consists of persistent hypertension with nonspecific symptoms, which may be interpreted as essential hypertension unless the associated pattern is recognized.

The medical history commonly reveals palpitations, exercise intolerance, dyspnea, chest pain, a sensation of somatic anxiety and sleep disturbances, in addition to adrenergic crises. Headache is typically severe and may be associated with pallor and sweating. Some patients report weight loss, nausea, abdominal or lumbar pain and, in rare cases, symptoms related to acute complications such as focal neurological deficits or syncope. Hyperglycemia may present as a sudden deterioration of pre-existing diabetes or as a new diagnosis in a patient without a significant metabolic history.

The physical examination may reveal sustained hypertension or a hypertensive crisis during the visit, tachycardia, pallor and diaphoresis. However, a relatively normal physical examination between attacks is not uncommon, particularly when secretion is episodic. Orthostatic hypotension may occur because of volume depletion and altered adrenergic regulation and should be actively assessed, as it has both diagnostic and therapeutic implications, particularly during preparation with alpha blockers.

In patients with greater catecholamine exposure, signs of target-organ damage may emerge, including arrhythmias, signs of heart failure, functional murmurs caused by a hyperdynamic circulation, or neurological abnormalities following ischemic or hemorrhagic events. During pregnancy, the presentation may be confused with gestational hypertension or preeclampsia, but the presence of adrenergic crises, severe headache and blood pressure instability should maintain a high level of suspicion, because management and prognosis change substantially when the correct diagnosis is made.

An important clinical consideration is that some pheochromocytomas may be minimally symptomatic and present only through complications, such as sudden cardiomyopathy, severe arrhythmias or a perioperative hypertensive crisis. Clinical presentation should therefore not be interpreted rigidly. Suspicion should arise from the combination of symptoms, blood pressure instability, cardiovascular comorbidities and the presence of an adrenal mass, because timely recognition allows appropriate preoperative preparation and markedly reduces morbidity.

Pheochromocytoma should be suspected in the presence of a compatible adrenergic phenotype, particularly when symptoms are episodic and associated with blood pressure instability. A combination of headache, palpitations and sweating during recurrent episodes is suggestive, but the diagnosis cannot be based solely on a “classic” pattern because many patients do not present with the complete triad or have milder symptoms. Suspicion should remain high in patients with paroxysmal hypertension, resistant hypertension, hypertensive crises triggered by stress, anesthesia or procedures, and orthostatic hypotension with supine hypertension, which reflects dysregulation of vascular control.

The setting of an adrenal incidentaloma is among the most important. When an adrenal mass is present, excluding a secreting chromaffin tumor is a priority because failure to identify it before surgery or biopsy may expose the patient to potentially fatal catecholaminergic crises. Even in patients with cancer, in whom the differential diagnosis includes metastasis, pheochromocytoma should not be overlooked when imaging and clinical findings are compatible, because perioperative and diagnostic management is radically different.

Suspicion should be particularly strong in young patients with severe hypertension or a family history of chromaffin tumors, and in cases with features suggesting a genetic predisposition, such as multifocality, bilateral disease or association with other endocrine tumors. In patients with sudden cardiomyopathy, complex arrhythmias or a Takotsubo-like syndrome without an evident trigger, catecholamine testing may be strategically important because the underlying cause is potentially correctable through tumor resection after adequate preparation.

Finally, suspicion should also include metabolic scenarios. Rapid deterioration in glycemic control, particularly when associated with adrenergic symptoms or blood pressure instability, may indicate catecholamine hypersecretion. Unintentional weight loss accompanied by labile hypertension and autonomic symptoms should also prompt targeted endocrine evaluation. Once raised, suspicion should rapidly lead to appropriate biochemical investigations and an orderly diagnostic sequence, because prevention of acute complications depends on timely identification.

The diagnosis of pheochromocytoma requires a structured pathway beginning with biochemical evidence of catecholamine hypersecretion and continuing with anatomical localization and, when indicated, functional and genetic characterization. The key principle is that diagnosis should not be based on isolated measurements of plasma or urinary catecholamines, because secretion may be episodic and false-positive results are common. International recommendations identify measurement of plasma free metanephrines or fractionated urinary metanephrines as first-line tests because metanephrines reflect intratumoral production and provide high sensitivity.

Preanalytical accuracy is crucial. Stress, non-standardized posture, interfering medications and acute illness may alter test results, and the choice between plasma and urine testing should be tailored to the patient and logistical circumstances. When values are markedly elevated, the diagnostic probability is high and localization may proceed. When elevations are mild or borderline, cautious interpretation is required, including repetition of testing under optimal conditions, review of medications and, in selected cases, second-line tests to reduce uncertainty.

Diagnostic evaluation of pheochromocytoma

• Biochemical confirmation: measurement of plasma free metanephrines or fractionated urinary metanephrines, with attention to preanalytical conditions and pharmacological interference.
• Anatomical localization: abdominal CT or MRI to define the location, size and characteristics of the adrenal mass, integrating structural imaging with the biochemical profile.
• Functional imaging when indicated: use of appropriate nuclear medicine techniques for staging, identification of multifocal or metastatic disease, and guidance of therapeutic decisions in selected cases.
• Genetic evaluation: systematic consideration of genetic testing and counseling, with implications for follow-up, screening for associated tumors and family assessment.

After biochemical confirmation, localization is based on structural imaging. CT is often the first step because of its availability and anatomical detail, whereas MRI is particularly useful in specific settings, including the need to reduce radiation exposure, pregnancy or more accurate characterization of tissues and anatomical relationships. Radiological features may be suggestive but do not replace biochemical assessment, because an adrenal mass may be non-secretory and perioperative management requires confirmation of a catecholaminergic phenotype before any manipulation.

Functional imaging is used when multifocal disease, extra-adrenal disease, recurrence or metastases are suspected, or when anatomical imaging is inconclusive. The choice of tracer depends on the clinical setting, biochemical phenotype and suspected genetic background because different biological variants display distinct metabolic behaviors. In selected cases, functional imaging also has a therapeutic role by directing radiometabolic treatment when the disease is unresectable or metastatic.

A fundamental diagnostic issue is assessment of the risk of persistent or metastatic disease, which cannot be completely excluded at the time of initial diagnosis. Staging should be individualized according to tumor size, location, clinical pattern, biochemical markers and genetic suspicion. This guides surgical planning and determines follow-up intensity because some patients will develop recurrences or new lesions over time, particularly in hereditary settings.

Finally, the diagnostic process must include preparation for therapeutic management. Once pheochromocytoma has been established, surgical planning and pharmacological preparation become integral parts of the diagnostic pathway because preoperative stabilization markedly reduces perioperative risk. Diagnosis is therefore not an isolated event but the beginning of a coordinated and sequential pathway that integrates biochemistry, imaging, genetics and treatment into a single clinical strategy.

The classification of pheochromocytoma is clinically useful when it connects tumor biology, risk and therapeutic strategy. A first distinction concerns the secretory pattern and catecholamine profile. Tumors with predominantly noradrenergic secretion tend to present with sustained hypertension and marked vasoconstriction, whereas those with a greater adrenergic component may cause more tachycardia, palpitations and blood pressure variability. This is not merely theoretical because it influences clinical presentation, tolerability and, to some extent, preoperative pharmacological management.

A second classification dimension concerns location and extent. Pheochromocytoma is, by definition, adrenal, but chromaffin disease may be multifocal and associated with paragangliomas. The presence of multiple lesions, bilateral disease or recurrences suggests a genetic predisposition and requires more complex surgical decisions, including cortical-sparing strategies in selected patients to reduce the risk of permanent adrenal insufficiency.

Clinical severity is primarily determined by cardiovascular impact and the presence of complications. Relatively stable forms, in which symptoms and blood pressure can be controlled, can be distinguished from high-risk forms characterized by recurrent hypertensive crises, arrhythmias, catecholamine-induced cardiomyopathy or cerebrovascular events. In these situations, treatment timing and the intensity of preoperative preparation become important prognostic determinants because rapidly reducing catecholamine burden and stabilizing hemodynamics lowers perioperative complications and mortality.

A modern conceptual point is that the adjective “benign” does not represent a reliable category. Current classification recognizes an intrinsic metastatic potential, and prognosis depends on the development of metastases in sites where chromaffin tissue is not normally present. Risk stratification is based on clinical and genetic characteristics and on behavior over time rather than on a single histological label. This perspective shifts attention toward long-term follow-up and identification of patients requiring more intensive surveillance.

Finally, classification must include the hereditary dimension. The presence of a pathogenic germline variant changes the probability of new lesions, the distribution of tumor sites, the risk of metastases in specific settings and the follow-up strategy. Severity therefore concerns not only the current event but also future risk and the need for structured, continuous surveillance capable of protecting the patient over time and enabling early diagnosis of new disease manifestations.

Treatment of pheochromocytoma is primarily surgical, but surgery must be preceded by careful pharmacological preparation to prevent intraoperative catecholaminergic crises and severe hypotension after resection. The therapeutic strategy is based on three pillars: preoperative adrenergic blockade, optimization of intravascular volume and complete resection of the lesion whenever possible. Management should take place in an experienced center because reduction of perioperative morbidity depends on the quality of preparation and anesthetic management.

The cornerstone of preparation is alpha-adrenergic blockade, which reduces vasoconstriction and stabilizes blood pressure. The choice between non-selective and selective agents depends on the clinical setting and the center’s experience, but the objective is the same: reducing blood pressure peaks, controlling symptoms and allowing intravascular volume expansion. After adequate alpha-blockade, a beta blocker may be added when required for tachycardia or arrhythmias. Beta-blockade should never be initiated without prior alpha-blockade because this may precipitate unopposed vasoconstriction and a hypertensive crisis.

Preoperative management also includes volume expansion through adequate sodium and fluid intake because chronic vasoconstriction often causes intravascular volume depletion. This measure reduces the risk of postoperative hypotension when the catecholaminergic signal is abruptly removed. In selected patients with marked hypersecretion or severe instability, specific drugs that reduce catecholamine synthesis may be considered to further lower intraoperative risk and improve clinical stability before surgery.

Minimally invasive adrenalectomy is the preferred approach for most adrenal pheochromocytomas when tumor size and characteristics do not suggest local invasion. An open approach is indicated when invasion is suspected or in large tumors with greater surgical complexity, and the choice should prioritize oncological safety and reduction of the risk of tumor rupture or incomplete resection. In patients with hereditary predisposition, bilateral disease or a high risk of new lesions, cortical-sparing surgery may be considered in experienced centers to reduce the likelihood of permanent adrenal insufficiency, balancing this benefit against the risk of local recurrence.

Metastatic or unresectable disease requires a multimodal treatment strategy. Management includes continued adrenergic blockade to control catecholamine-related symptoms, evaluation of systemic therapies and, in selected settings, radiometabolic approaches guided by functional imaging. The aim is to reduce tumor burden or secretory activity, improve quality of life and stabilize the disease. Treatment selection depends on the location of metastases, rate of progression, genetic profile and availability of therapeutic options within a specialist setting.

At every stage, treatment must include integrated management of cardiovascular and metabolic complications. Blood pressure control, treatment of arrhythmias, optimization of glycemic control and cardiological assessment when indicated are as integral to treatment as tumor resection. An effective therapeutic pathway is one that makes surgery safe and, after resection, supports the patient through monitoring of residual risk and prevention of recurrences or new lesions, particularly in hereditary settings.

Follow-up of pheochromocytoma is essential because there is a clinically meaningful risk of recurrence, new lesions and, in some patients, the development of metastases over time. Surveillance should be individualized according to risk factors such as age at diagnosis, tumor size, bilateral disease, multifocality, genetic profile and the presence of extra-adrenal disease. A fundamental principle is that surveillance should not be limited to the first few years after surgery because late events may occur, and prevention of complications depends on the ability to detect recurrent catecholamine secretion at an early stage.

Biochemical follow-up is based on monitoring metanephrines, with testing frequency tailored to the individual risk profile. After complete resection, biochemical normalization confirms the effectiveness of surgery, but subsequent testing is required to detect recurrence or new lesions. The choice between plasma and urine testing may follow practical and performance-related considerations, but consistency over time should be maintained to facilitate longitudinal comparison. When borderline results occur, interpretation should consider preanalytical conditions and pharmacological interference, avoiding premature conclusions while not delaying further investigation when suspicion is justified.

Radiological and functional follow-up depends on the clinical context. In low-risk patients with complete resection, imaging may be less frequent and guided by biochemical findings and clinical symptoms. In high-risk patients, particularly those with genetic predisposition, multifocality or features associated with metastatic risk, surveillance may include periodic imaging and, when appropriate, functional techniques to identify subclinical lesions and guide early treatment. The selected method should be consistent with the biological profile and with the need to minimize long-term radiation exposure when relevant.

The genetic component strongly influences follow-up. In patients with pathogenic germline variants, surveillance concerns not only the original tumor site but also the possibility of multiple tumors and associated manifestations. Follow-up should therefore be incorporated into a pathway that includes genetic counseling, assessment of relatives when indicated and structured surveillance plans. This approach enables earlier diagnosis and reduces the risk of catastrophic presentations caused by unrecognized tumors.

Finally, monitoring should include cardiovascular and metabolic status. Even after resection, recovery of blood pressure and glycemic control may take time and may not be complete, particularly when target-organ damage or long-standing hypertension was present. Cardiological assessment may be required in patients with catecholamine-induced cardiomyopathy or arrhythmias, and integrated management reduces long-term event risk. Effective follow-up combines disease surveillance with treatment of its consequences, ensuring clinical continuity and prevention of complications.

The prognosis of pheochromocytoma is generally favorable when diagnosis is timely, preoperative preparation is adequate and resection is complete. Most patients experience a substantial reduction in adrenergic symptoms and improvement in blood pressure. However, prognosis depends on factors including recurrence risk, the presence of a genetic predisposition and the development of metastases. Because metastatic potential cannot be definitively excluded at presentation, prognosis should be considered longitudinally, with structured follow-up forming an integral part of the outcome.

The most important complications are cardiovascular. Hypertensive crises may cause hemorrhagic or ischemic stroke, aortic dissection, myocardial ischemia and malignant arrhythmias. Catecholamine-induced cardiomyopathy may present as acute ventricular dysfunction and, in some cases, regress after tumor resection, but it may leave residual impairment when exposure has been prolonged or ischemic events have occurred. Atrial fibrillation and other arrhythmias may persist in patients with pre-existing heart disease, and management should be coordinated between endocrinology and cardiology to reduce thromboembolic risk and improve hemodynamic stability.

Metabolic complications include hyperglycemia and diabetes, which often improve after surgery, although reversibility depends on the duration of the abnormality and the presence of pre-existing insulin resistance. Weight loss and catabolism may also regress after removal of the catecholaminergic signal, but frail patients may require rehabilitation and nutritional optimization. From a neuropsychological perspective, somatic anxiety, insomnia and hypervigilance may persist for a period and affect quality of life, making integrated clinical support useful.

Perioperative complications represent a crucial category. Without diagnosis and preparation, tumor manipulation during surgery or anesthesia may trigger hypertensive crises and severe arrhythmias. Even with adequate preparation, postoperative hypotension may occur because of the abrupt removal of the catecholaminergic signal and pre-existing volume depletion, which is why immediate intensive monitoring is an integral part of treatment. In experienced hands, preparation with alpha-blockade and volume optimization markedly reduces these risks but requires rigorous adherence to the management pathway.

In the long term, the most relevant complication is recurrence or the development of new lesions, particularly in patients with a genetic predisposition. The possibility of metastases requires appropriate surveillance and, when necessary, multimodal management. In summary, pheochromocytoma is often curable, but optimal prognosis depends on accurate diagnosis, rigorous preoperative preparation, resection in experienced centers and follow-up tailored to individual risk, with particular attention to hereditary cases and patients with factors associated with future tumor-related events.