Pheochromocytoma

Pheochromocytoma is a rare neuroendocrine tumor arising from chromaffin cells of the adrenal medulla that secretes catecholamines, leading to potentially life-threatening hypertension and cardiovascular complications. Also called paraganglioma when it arises from extra-adrenal chromaffin tissue, the collective term PPGL ( pheochromocytoma and paraganglioma ) is now standard. Historical synonyms include the "10% tumor" (referring to approximate rates of bilaterality, extra-adrenal location, malignancy, and familial occurrence), though these proportions are now known to vary substantially by genetic background.

Terminology and Classification

Throughout this article, pheochromocytoma refers strictly to adrenal medullary tumors, while paraganglioma denotes extra-adrenal sympathetic or parasympathetic tumors. Malignant pheochromocytoma is defined by the presence of metastasis, not by histologic features alone. Hereditary PPGL syndromes include multiple endocrine neoplasia type 2 (MEN2A and MEN2B), von Hippel-Lindau disease (vHL), neurofibromatosis type 1 (NF1), and succinate dehydrogenase (SDHx) germline mutations ^[7]D5. Catecholamine crisis describes a paroxysm of severe hypertension, arrhythmia, or myocardial ischemia triggered by tumor catecholamine release.

Epidemiology

Pheochromocytoma is rare, with a reported incidence of 2 to 8 cases per million person-years globally, though this likely underestimates true prevalence due to frequent underdiagnosis ^[5]B2c. The tumor accounts for fewer than 10% of adrenal incidentalomas in endocrine referral populations ^[1]A1c. Incidence rises with age, peaking in the fourth to fifth decades, with no clear sex predominance ^[5]B2c[11]D5. In children, pheochromocytoma is even rarer and is more often associated with hereditary syndromes such as vHL or SDHx mutations ^[7]D5.

Geographic variation is poorly characterized, but population-based studies from Europe and North America report similar incidence rates ^[5]B2c. Mortality data are limited; however, undiagnosed or untreated pheochromocytoma carries a high risk of fatal hypertensive crisis, myocardial injury, and stroke ^[9]D5. Malignant PPGL (approximately 10-15% of cases) has a 5-year survival of 40-50%, though this topic is detailed in the Prognosis section.

Clinical Significance

Although most pheochromocytomas are benign, their catecholamine secretion can provoke severe hypertensive crises, myocardial injury, and death if unrecognized ^[9]D5. Early diagnosis and resection are curative in the majority of sporadic cases, making pheochromocytoma a rare but curable cause of secondary hypertension.

Pearl: Pheochromocytoma is a rare but curable cause of hypertension; a high index of suspicion is essential because delayed diagnosis carries a high risk of cardiovascular morbidity and mortality ^[5]B2c[9]D5.

The annual incidence of pheochromocytoma and paraganglioma (PPGL) is estimated at 0.6 to 1.0 per 100,000 person-years, though detection rates have risen with the widespread use of cross-sectional imaging ^[12]A1c. PPGLs account for approximately 0.1% to 0.2% of all hypertensive patients, but this proportion increases to 1% to 2% among those with resistant or paroxysmal hypertension ^[15]D5[22]C4. The median age at diagnosis is 40 to 50 years, with a slight female predominance (approximately 55% female) ^{[16]B2b[21]C4}. No consistent seasonal variation has been reported.

Genetic Risk Factors

Up to 40% of PPGLs are hereditary, driven by germline mutations in at least 20 susceptibility genes ^[20]B2b. The most common include VHL, RET, NF1, SDHB, SDHD, SDHA, TMEM127, MAX, and SDHAF2 ^[7]D5[20]B2b. These mutations confer varying degrees of risk and age-related penetrance. For example, SDHB mutations carry a high lifetime risk of metastatic disease (up to 50%), while SDHA mutations have lower penetrance but still warrant surveillance ^[20]B2b. The table below summarizes key genetic risk factors.

Hereditary Syndromes and Penetrance

Penetrance is age-dependent and gene-specific. For VHL, pheochromocytoma typically presents in the third to fourth decade, but surveillance starting in childhood is recommended because tumors can occur before age 10 ^[7]D5[19]B2b. In MEN2, pheochromocytoma often develops after medullary thyroid carcinoma, with a median age of 30 to 40 years ^[12]A1c. SDHB mutation carriers have a cumulative risk of PPGL of approximately 30% by age 60, with a high proportion of malignant disease ^[20]B2b. Genetic testing is recommended for all patients with PPGL, and cascade testing of at-risk relatives enables early detection and prevention ^{[12]A1c[20]B2b}.

Prevention and Screening

Prevention centers on identifying at-risk individuals through genetic counseling and initiating surveillance before clinical symptoms arise. The NCCN and Endocrine Society guidelines recommend that all patients with PPGL undergo germline genetic testing ^{[12]A1c[20]B2b}. For mutation carriers, surveillance includes annual biochemical testing (plasma or urinary metanephrines) and imaging (MRI or CT) every 1 to 2 years ^[7]D5[12]A1c. Whole-body MRI is increasingly used for hereditary syndromes with multisite tumor risk, such as VHL and SDHx, because it avoids radiation exposure ^[14]B2b. The USPSTF does not recommend population-based screening for PPGL, as the low prevalence and lack of evidence for benefit in asymptomatic individuals do not support it. However, targeted screening in patients with suggestive symptoms, resistant hypertension , or a family history of PPGL is strongly advised ^[15]D5[22]C4.

Pearl: Up to 40% of PPGLs are hereditary; genetic testing in all patients and surveillance of mutation carriers with annual metanephrines and imaging every 1-2 years can prevent hypertensive crises and detect tumors at an early, curable stage ^{[7]D5[12]A1c[20]B2b}.

All pheochromocytomas harbor metastatic potential, but histologic features and underlying molecular drivers stratify risk and guide therapeutic decisions ^[25]D5[34]D5. Routine hematoxylin and eosin staining reveals the characteristic Zellballen pattern: nests of polygonal chief cells surrounded by sustentacular cells ^[27]D5. Cytologic atypia, necrosis, vascular invasion, and increased mitotic activity are key features that raise concern for aggressive behavior ^[27]D5[34]D5.

Histologic Grading Systems

The Pheochromocytoma of the Adrenal Gland Scaled Score (PASS) uses 12 histologic criteria; a score of ≥4 identifies higher-risk tumors, though interobserver variability limits its standalone use ^[35]C4. The Grading of Adrenal Pheochromocytoma and Paraganglioma (GAPP) system incorporates Ki67 proliferation index, catecholamine type, and histologic pattern, providing a more reproducible risk assessment ^[34]D5. Ki67 >3% is an independent predictor of metastatic behavior ^[28]D5[34]D5.

Immunohistochemistry and SDH Deficiency

Immunohistochemistry for succinate dehydrogenase subunit B (SDHB) is a critical surrogate for SDHx mutations: loss of SDHB expression indicates a germline or somatic alteration in SDHA, SDHB, SDHC, SDHD, or SDHAF2 ^[26]D5[39]D5. SDH-deficient tumors are associated with a pseudohypoxic phenotype and higher metastatic risk, particularly with SDHB mutations ^[28]D5[39]D5. Other markers include chromogranin A, synaptophysin, and GATA3, which confirm neuroendocrine differentiation ^[27]D5.

Molecular Classification

Pan-genomic studies classify pheochromocytomas into three main clusters ^[29]D5:

Genotype-Phenotype Correlations

Germline mutations account for approximately 40% of pheochromocytomas ^[30]C4. SDHB mutations carry the highest metastatic risk (up to 50% for abdominal paragangliomas) ^[28]D5. RET mutations in MEN2 typically produce bilateral, low-risk pheochromocytomas ^[37]D5. VHL mutations are associated with multiple, often synchronous tumors ^[29]D5. Rare drivers include MDH2, which disrupts the Krebs cycle and induces pseudohypoxia ^[30]C4.

Implications for Prognosis and Therapy

Histologic grading and molecular profiling are complementary: PASS ≥4 or GAPP high-risk combined with SDHB loss identifies patients needing intensive surveillance ^[28]D5[35]C4. In metastatic disease, cluster 1 tumors may respond to radionuclide therapy (177Lu-DOTATATE) or hypoxia-directed agents, while cluster 2 tumors may benefit from kinase inhibitors ^[36]D5. RET-mutated tumors are candidates for selective RET inhibitors (e.g., selpercatinib) ^[37]D5.

Pearl: Histologic grading (PASS ≥4) and SDHB immunohistochemistry are essential for risk stratification; molecular cluster classification guides systemic therapy selection in metastatic disease ^{[28]D5[35]C4[36]D5}.

Headache, palpitations, and diaphoresis constitute the classic triad, but fewer than half of patients present with all three symptoms ^[48]D5. The clinical spectrum ranges from incidentally discovered adrenal masses to life-threatening hypertensive crises, with symptom severity reflecting the pattern and magnitude of catecholamine excess rather than tumor size ^[46]D5.

Presenting Symptoms

Paroxysmal symptoms, sudden-onset headache, palpitations, diaphoresis, pallor, and anxiety, are the hallmark, often triggered by physical activity, micturition (for bladder paragangliomas), or certain medications ^[48]D5. Sustained hypertension occurs in 50-60% of patients, while 10-20% are normotensive ^[46]D5. Orthostatic hypotension may result from chronic vasoconstriction and volume contraction. Symptoms typically progress over weeks to months, but some patients remain asymptomatic for years, with tumors discovered incidentally on imaging ^[23]D5.

Neurological Examination Findings

Between paroxysms, the examination may be entirely normal. During a crisis, findings include systolic BP > 180 mmHg, tachycardia, pallor, and diaphoresis. Hypertensive retinopathy (arteriolar narrowing, hemorrhages, papilledema) may be present in chronic cases. Mass effect from large adrenal tumors can cause abdominal tenderness; head and neck paragangliomas may present as a pulsatile neck mass with cranial nerve deficits (e.g., Horner syndrome, vocal cord palsy) ^[52]C4.

Phenotypic Variants

The genetic background strongly influences presentation. A table summarizes key variants:

Bilateral adrenal involvement is a strong clue for hereditary disease, particularly MEN2 and VHL ^[41]B2b.

Red Flags

Pheochromocytoma crisis is a medical emergency characterized by severe hypertension, arrhythmias, myocardial ischemia, stroke, or pulmonary edema. Triggers include surgery, anesthesia, contrast media, and glucocorticoids, methylprednisolone has been reported to precipitate cardiac arrest ^[53]C4. Any patient with unexplained hemodynamic instability after such triggers should be evaluated for pheochromocytoma. Plasma metanephrines > 4-fold the upper reference limit are highly suggestive and warrant urgent imaging ^[23]D5.

Atypical Presentations

Atypical presentations are common and lead to misdiagnosis. Pheochromocytoma may mimic panic disorder, hyperthyroidism, or preeclampsia ^[48]D5. Rarely, it presents solely with progressive lower extremity necrosis, as in a case misdiagnosed as allergic vasculitis for 24 years ^[44]C4. In pregnancy, symptoms overlap with gestational hypertension, delaying diagnosis and increasing maternal-fetal risk ^[45]D5. Asymptomatic incidentalomas account for up to 30% of cases, underscoring the need for biochemical screening in all adrenal masses ^[23]D5.

Pearl: The classic triad of headache, palpitations, and diaphoresis is present in fewer than half of patients; a high index of suspicion is needed for atypical presentations, and any patient with unexplained hypertensive crises or incidental adrenal mass should undergo plasma metanephrine testing ^[23]D5[48]D5.

Percutaneous core needle biopsy plays a limited role in the routine diagnosis of pheochromocytoma and paraganglioma (PPGL). Biochemical confirmation of catecholamine excess and cross-sectional imaging (CT/MRI) establish the diagnosis preoperatively with high confidence in most patients ^[25]D5. Biopsy is reserved for specific scenarios: suspected metastatic disease requiring tissue for molecular profiling, technically unresectable tumors where tissue diagnosis guides systemic therapy, or atypical presentations where the imaging differential includes adrenocortical carcinoma , renal cell carcinoma , or metastasis from another primary ^[56]D5.

Catecholamine-Related Complications

The longstanding caution against biopsy stems from fear of a catecholamine crisis triggered by needle trauma. A systematic review and individual patient meta-analysis of 86 patients undergoing core needle biopsy for PPGL found no procedure-related deaths and a complication rate requiring intervention or hospitalization of 7% (6/86) ^[54]A1a. Among patients with metastatic disease (34% of the cohort), the complication rate was not significantly higher. Although the absolute risk is low, all patients should receive preoperative alpha-blockade (phenoxybenzamine 10-20 mg orally BID or doxazosin 2-8 mg daily, titrated to blood pressure) before biopsy, and the procedure should be performed with an 18-gauge or smaller needle under ultrasound or CT guidance using a coaxial technique to minimize tract trauma ^[54]A1a.

Histologic Hallmarks

On routine hematoxylin and eosin staining, PPGLs show characteristic Zellballen, nested clusters of polygonal chief cells with granular basophilic to amphophilic cytoplasm, separated by a delicate fibrovascular stroma containing sustentacular cells ^[56]D5. The nuclei are round to oval with coarse chromatin; pleomorphism can be marked but does not by itself indicate malignant potential. The 4th edition of the WHO classification reclassified all PPGLs as malignant neoplasms with variable metastatic potential, abandoning the terms "benign" and "malignant" ^[57]D5. Instead, the PASS (Pheochromocytoma of the Adrenal Scaled Score) or the GAPP (Grading System for Adrenal Pheochromocytoma and Paraganglioma) scoring systems are used to stratify risk of metastasis based on histologic features (capsular invasion, vascular invasion, necrosis, mitotic count, cellularity, and atypical mitotic figures) ^[57]D5.

Immunohistochemistry and Molecular Testing

Immunohistochemistry (IHC) is essential for both diagnosis and germline risk stratification.

SDHB IHC is particularly critical: negative (absent) staining signals an underlying germline mutation in one of the SDH subunit genes (SDHA, SDHB, SDHC, SDHD, or SDHAF2), which has major implications for surveillance of synchronous or metachronous paragangliomas, renal cell carcinoma, and gastrointestinal stromal tumors ^[59]D5[60]D5. SDHB-deficient PPGLs also show distinctive vacuolated eosinophilic cytoplasm on H&E, mirroring the morphology of SDH-deficient renal cell carcinoma ^[59]D5.

Composite Pheochromocytoma

A rare variant, composite pheochromocytoma, contains both conventional pheochromocytoma and a neuroblastic component (most commonly ganglioneuroma, seen in 75.5% of reported cases) ^[55]C4. It accounts for fewer than 3% of all adrenal pheochromocytomas. Diagnosis requires identification of both components; the neuroblastic portion should be graded separately for risk stratification. Composite tumors are associated with neurofibromatosis type 1 in 13.6% of cases, and SDHB IHC is typically retained ^[55]C4.

Pearl: Biopsy of suspected PPGL is rarely necessary but can be performed safely with preoperative alpha-blockade and a coaxial 18-gauge needle; histology should always be paired with SDHB and PHOX2B immunohistochemistry, as SDHB loss identifies a heritable syndrome with high metastatic risk and directs surveillance for syndromic tumors ^{[54]A1a[56]D5[60]D5}.

Anatomic imaging with CT or MRI is the first step in localizing a suspected pheochromocytoma, but functional imaging with PET tracers is essential for staging, detecting multifocal disease, and guiding therapy ^[64]A1c.

Anatomic Imaging

Adrenal protocol CT includes noncontrast, contrast-enhanced, and delayed phases. Pheochromocytomas typically show precontrast attenuation >10 Hounsfield units (HU), avid enhancement, and washout <50% (unlike lipid-rich adenomas) ^[69]B2b. On MRI, they appear T2 hyperintense (the "light bulb" sign), though this is not pathognomonic ^[74]C4. For initial staging, CT of the chest, abdomen, and pelvis with intravenous contrast is recommended by the ACR Appropriateness Criteria ^[64]A1c. MRI of the abdomen and pelvis without and with contrast is an alternative, particularly for patients with contraindications to iodinated contrast or for radiation-sensitive populations ^[64]A1c.

Functional Imaging

68Ga-DOTATATE PET/CT is now the preferred functional imaging modality for staging pheochromocytoma/paraganglioma (PPGL), with per-lesion sensitivity exceeding 95% in SDHB-associated metastatic disease ^[73]B2b. It targets somatostatin receptor 2 (SSTR2), which is overexpressed in PPGL, and outperforms 18F-FDG, 18F-FDOPA, and 123I-MIBG in head -to-head comparisons ^{[71]D5[73]B2b}. 18F-FDG PET/CT is complementary, showing higher uptake in aggressive, rapidly growing, or SDHB-mutant tumors; it also detects metabolically active brown adipose tissue, a common incidental finding in PPGL patients ^{[65]A1a[68]B2b}. 18F-FDOPA PET/CT has high sensitivity for head and neck paragangliomas but lower sensitivity for metastatic SDHB-related disease (per-patient sensitivity ~80%) ^{[66]B2a[67]A1a}. 123I-MIBG scintigraphy remains useful for selecting patients who may benefit from 131I-MIBG targeted radionuclide therapy ^[72]D5.

Surveillance Imaging

For patients with hereditary syndromes (e.g., SDHB, VHL, MEN2, MAX, TMEM127), whole-body MRI (WB-MRI) every 2-3 years is recommended for surveillance of multifocal disease, avoiding cumulative radiation exposure ^[14]B2b. For sporadic cases, CT or MRI of the abdomen and pelvis every 1-2 years is appropriate ^[64]A1c. Functional imaging (68Ga-DOTATATE PET/CT) is reserved for suspected recurrence, rising biomarkers, or metastatic progression ^[64]A1c.

Pearl: For initial staging of pheochromocytoma/paraganglioma, 68Ga-DOTATATE PET/CT is the preferred functional imaging modality, particularly in SDHB mutation carriers, while whole-body MRI is recommended for surveillance in hereditary syndromes ^{[14]B2b[64]A1c[73]B2b}.

Plasma free metanephrines provide the highest diagnostic sensitivity for PPGL, but molecular biomarkers now extend beyond diagnosis to prognostication and therapeutic targeting.

Biochemical Diagnostics

Plasma free metanephrines (normetanephrine, metanephrine, and methoxytyramine) are the first-line diagnostic test, with sensitivity exceeding 96% ^[47]B2b. However, false positives are common due to medications (tricyclic antidepressants, beta-blockers) and chronic illness ^[47]B2b. The clonidine suppression test (CST) can confirm PPGL when plasma normetanephrine is elevated but metanephrine is normal; a post-clonidine normetanephrine level >0.71 nmol/L has 100% specificity ^[80]B2b. Chromogranin A (CgA) is an adjunctive serum marker with pooled sensitivity 82% and specificity 88% for PPGL, though it is less specific than metanephrines ^[81]A1a.

Immunohistochemical Biomarkers

Immunohistochemistry (IHC) on tumor tissue provides diagnostic and prognostic information. SDHB IHC is a surrogate for SDHx mutation status: loss of SDHB expression indicates an SDH-deficient tumor, which carries higher metastatic risk ^[82]B2b. CA9 overexpression also correlates with SDH deficiency and pseudohypoxic signaling ^[82]B2b. Ki-67 proliferation index is a component of the GAPP (Grading System for Adrenal Pheochromocytoma and Paraganglioma ) score; a Ki-67 >3% is associated with metastatic progression ^[86]B3b. INSM1 is a sensitive and specific neuroendocrine marker that reliably distinguishes pheochromocytoma from adrenal cortical lesions (sensitivity 97%, specificity 100%) ^[89]B3b.

DNA Methylation and Genomic Markers

Genome-wide DNA methylation profiling reveals distinct clusters associated with metastatic behavior. Hypermethylation of specific CpG islands, including TERT promoter methylation, is enriched in metastatic PPGL and can be detected by pyrosequencing ^{[82]B2b[87]B3b}. These epigenetic markers may complement histologic grading to identify high-risk patients.

Predictive Biomarkers for Targeted Therapy

Molecular profiling guides therapeutic decisions. SDH-deficient tumors (SDHB IHC loss) are sensitive to hypoxia-inducible factor (HIF) inhibitors and may respond to belzutifan (HIF-2alpha inhibitor) ^[82]B2b. Tumors with RET or NF1 mutations may be candidates for tyrosine kinase inhibitors. MIBG avidity on scintigraphy predicts response to high-dose [131I]MIBG therapy, which achieved a 22% objective response rate in metastatic PPGL ^[79]C4.

NCCN/CAP Testing Recommendations

The NCCN recommends germline genetic testing for all patients with PPGL, given the high prevalence of hereditary syndromes (up to 40%) ^[25]D5. The College of American Pathologists (CAP) endorses SDHB IHC as a first-line screening tool for SDHx mutations, with reflex to germline sequencing if IHC is lost ^[82]B2b. Tumor molecular profiling (including SDHB, ATRX, and TERT promoter methylation) is recommended for all resected PPGL to stratify metastatic risk and identify actionable targets ^{[25]D5[82]B2b}.

Pearl: Plasma free metanephrines remain the diagnostic gold standard, but SDHB immunohistochemistry and TERT promoter methylation are emerging as key biomarkers for metastatic risk stratification and targeted therapy selection ^{[82]B2b[87]B3b}.

Metastatic spread is the only definitive criterion for malignancy in pheochromocytoma and paraganglioma (PPGL); no histologic grading system can reliably predict behavior. The first official tumor, node, metastasis ( TNM ) staging classification for PPGL was published by the American Joint Committee on Cancer ( AJCC ) in its 8th edition, replacing decades of ad hoc descriptors ^[98]D5. This system unifies terminology across institutions and directly informs prognosis and treatment planning.

AJCC 8th Edition TNM Classification

The staging applies separately to pheochromocytoma and paraganglioma (see table below). The T category is site-specific because tumor size and invasion patterns differ between adrenal and extra-adrenal primary sites. N and M categories are identical for both. Metastases (M1) automatically define Stage IV, regardless of T or N status, underscoring the primacy of metastatic detection ^[98]D5.

Source: AJCC Cancer Staging Manual, 8th edition (2017), as referenced in the staging discussion by Jimenez et al. ^[98]D5.

Stage Grouping

• Stage I: T1 N0 M0 (pheochromocytoma only; paraganglioma is always ≥stage II at diagnosis) ^[98]D5.
• Stage II: T2 N0 M0 (any primary with negative nodes and no metastases).
• Stage III: T1-T2 N1 M0 (any size with regional nodal involvement).
• Stage IV: Any T, any N, M1 (distant metastases). Stage IV is metastatic disease and carries the worst prognosis ^[91]D5[98]D5.

Clinical Implications of Staging

Staging determines the extent of required surgery, the need for adjuvant therapy, and the intensity of follow-up. For localized (Stage I-II) PPGL, complete surgical resection is curative in most cases. For Stage III disease, locoregional lymphadenectomy is essential because nodal involvement increases recurrence risk ^[92]A1c. Stage IV (metastatic) disease is incurable; management focuses on control of catecholamine excess, tumor debulking, and systemic therapy such as 131I-MIBG therapy or chemotherapy (e.g., cyclophosphamide - vincristine -dacarbazine) ^{[98]D5[103]C4}.

Approximately 10-20% of pheochromocytomas and 30-40% of paragangliomas (especially extra-adrenal, SDHB-mutated) are metastatic at presentation ^[100]D5. The risk of metastasis is higher in tumors harboring SDHB or FH mutations, large primary tumors (>5 cm), and those with ATRX mutations or TERT activation ^[101]C4.

Pitfalls in Staging

• No histologic prediction: Unlike many carcinomas, PPGL cannot be graded as "benign" or "malignant" by histology alone, only the presence of metastases establishes malignancy ^[91]D5.
• Imaging sensitivity: Anatomic imaging (CT/MRI) may miss small peritoneal or bone metastases. 18F-DOPA PET/CT or 68Ga-DOTATATE PET/CT are more sensitive for detecting nodal and distant disease and should be part of staging workup whenever feasible ^{[93]B2b[99]D5}.
• Extra-adrenal primary: Paragangliomas are often larger at diagnosis and more likely to be metastatic (Stage IV) at presentation than adrenal primaries ^[100]D5.

Pearl: The AJCC 8th edition TNM staging is the only validated classification for PPGL; Stage IV (any M1) is the only category that defines malignant disease and requires systemic rather than locally curative therapy ^[98]D5[91]D5.

Management of pheochromocytoma centers on three sequential phases: preoperative medical preparation to prevent intraoperative hypertensive crisis, complete surgical resection, and long-term surveillance for recurrence or metastasis. The approach is guided by tumor size, genetic background, and disease extent, with metastatic disease requiring a multimodal strategy.

Step 1: Preoperative Alpha-Adrenoceptor Blockade

Initiate a noncompetitive α1-blocker (phenoxybenzamine 10 mg PO twice daily, titrated to 20-40 mg three times daily) or a competitive α1-blocker (doxazosin 2-16 mg daily) at least 7-14 days before surgery ^[2]B2a. The goal is to achieve blood pressure <130/80 mmHg, heart rate 60-80 bpm, and orthostatic hypotension without symptoms. A systematic review confirms that α-blockade reduces intraoperative hemodynamic instability and is uniformly recommended by all international guidelines ^[2]B2a (2a). Add a β-blocker (e.g., propranolol 20-40 mg three times daily) only after adequate α-blockade to prevent unopposed α-mediated vasoconstriction. Do not use β-blockers first ^[2]B2a. For patients with paraganglioma, the same protocol applies, though some centers use a shorter duration ^[2]B2a.

Step 2: Surgical Resection

Laparoscopic adrenalectomy is the standard for tumors ≤6 cm without evidence of invasion ^{[106]A1b[13]A1a}. A randomized trial (N=100) found no significant difference in operative time between laparoscopic and robotic adrenalectomy (mean 95 vs 90 min, p=0.3), but robotic approach reduced blood loss (50 vs 80 mL, p=0.04) and hospital stay (2 vs 3 days, p=0.02) ^[106]A1b (1b). A GRADE-assessed meta-analysis of prospective RCTs confirms that robotic adrenalectomy offers shorter hospital stay and lower conversion rates, though operative time and costs are similar ^[13]A1a (1a). Retroperitoneal laparoscopic adrenalectomy is preferred for posterior tumors; a meta-analysis of 52 studies (N=9,218) showed shorter operative time (WMD -12 min, 95% CI -18 to -6) and less postoperative pain compared to transabdominal approach ^[111]A1a (1a). Partial adrenalectomy (cortical-sparing) is recommended for bilateral tumors or hereditary syndromes (e.g., MEN2, VHL) to preserve adrenal function; a meta-analysis of 19 studies (N=3,165) found similar recurrence rates (2.1% vs 1.8%) but lower adrenal insufficiency (0% vs 100%) with partial vs total adrenalectomy ^[8]B2a (2a). Open adrenalectomy is reserved for tumors >6 cm or with suspected invasion ^[119]B3b.

Step 3: Postoperative Monitoring

Monitor blood glucose hourly for 24 hours because hypoglycemia occurs in 15-30% of patients after tumor resection due to sudden catecholamine withdrawal ^[16]B2b. A nomogram incorporating preoperative metanephrine level and tumor size predicts risk (AUC 0.82) ^[16]B2b (2b). Check blood pressure every 15 minutes for the first 2 hours, then hourly for 24 hours; hypotension may require volume resuscitation. Do not discharge until blood pressure is stable without vasopressors.

Step 4: Management of Metastatic Disease

For unresectable or metastatic pheochromocytoma/paraganglioma, treatment is palliative and guided by tumor genotype and receptor expression.

Targeted radionuclide therapy (TRT) is first-line for somatostatin receptor (SSTR)-positive or MIBG-avid disease.

• High-specific-activity ¹³¹I-MIBG (Azedra): FDA-approved for metastatic pheochromocytoma/paraganglioma; a phase II study (N=50) reported objective response rate 22% (95% CI 12-36) and disease control rate 68% ^[79]C4 (4). Dose: 12 mCi/kg (range 492-1,160 mCi) with autologous stem cell support for doses >12 mCi/kg ^[79]C4.
• ¹⁷⁷Lu-DOTATATE (PRRT): A phase II trial (N=46) showed median progression-free survival (PFS) 20 months (95% CI 14-26) and overall survival 48 months (95% CI 36-60) ^[63]A1b (1b). Preferred for SSTR-positive tumors, especially SDHB-mutated ^[72]D5 (5).

Systemic therapies for progressive disease after TRT or if TRT-ineligible:

Emerging therapies under investigation:

• Pharmacologic ascorbic acid (high-dose IV vitamin C) targets redox imbalance in SDHB-mutated tumors; preclinical models show growth inhibition ^[114]D5 (5).
• PARP inhibitors (e.g., olaparib) exploit DNA repair dependency in cluster I tumors; a phase II trial is ongoing ^[115]D5 (5).
• ALK inhibitors (brigatinib) for ALK-mutant pheochromocytoma; a case report showed dramatic remission ^[112]D5 (5).

What NOT to do:

• Do not use β-blockers without prior α-blockade - risk of hypertensive crisis ^[2]B2a.
• Do not perform percutaneous biopsy of suspected pheochromocytoma - risk of catecholamine storm and hemorrhage.
• Do not use bicarbonate for intraoperative acidosis unless pH <7.1 - no evidence of benefit.

Controversies and Guideline Disagreement

Pearl: Preoperative α-blockade for 7-14 days is mandatory to prevent intraoperative hypertensive crisis; for metastatic disease, select TRT (¹³¹I-MIBG or ¹⁷⁷Lu-DOTATATE) based on receptor imaging, and consider belzutifan or cabozantinib-based combinations for progressive disease ^{[2]B2a[79]C4[63]A1b[105]B2b[107]B2b}.

Prognosis in pheochromocytoma hinges on two distinct outcomes: the immediate perioperative risk from catecholamine excess and the long-term risk of metastatic progression. With modern preoperative α-blockade and experienced surgical teams, perioperative mortality is <2% ^[120]A1b. Complete tumor resection achieves biochemical cure in >95% of patients with localized disease ^[123]B2a. However, 5-year overall survival for metastatic pheochromocytoma ranges from 40% to 60% ^[124]B3b, with anatomic site independently influencing prognosis: thoracic primaries carry the best outcomes, while abdominal extra-adrenal tumors have the worst ^[124]B3b.

Overall Survival and Recovery

Recovery from surgery typically occurs over 4-6 weeks, with normalization of catecholamine levels within days. Long-term surveillance is recommended for at least 10 years due to risk of late recurrence. For patients with metastatic disease, median progression-free survival is approximately 12-18 months with systemic therapy, though responses to belzutifan (HIF-2α inhibitor) have shown promise: in a phase 2 trial, the objective response rate was 25% and median PFS was 13.8 months ^[105]B2b. Peptide receptor radionuclide therapy ( PRRT ) with ¹⁷⁷Lu-DOTATATE yields disease control rates of 80-90% and median PFS of 20-30 months in selected patients ^[63]A1b. High-dose MIBG therapy achieves a 5-year survival of 45-55% in those with MIBG-avid disease ^[79]C4.

Prognostic Factors

The strongest predictor of metastatic behavior is a germline SDHB mutation, which confers a 30-50% lifetime risk of metastasis ^[101]C4. Other molecular markers include ATRX mutations and TERT promoter activation, both independently associated with metastatic progression (HR 3.2 and 4.1, respectively) ^[101]C4. A prospective study (COMETE-TACTIC) identified that a combination of SDHB immunohistochemistry loss, TERT promoter methylation, and metabolomic profiling (succinate accumulation) improved prediction of metastatic status with an AUC of 0.89 ^[82]B2b. Age >50 years at diagnosis is associated with worse survival (HR 1.8) ^[126]B3b. Tumor size >5 cm, extra-adrenal location, and high Ki-67 index (>3%) are also adverse features ^[124]B3b.

Long-Term Sequelae and Recurrence

Even after successful resection, 10-20% of patients have persistent hypertension requiring ongoing antihypertensive therapy ^[123]B2a. Fatigue, anxiety, and post-traumatic stress related to hypertensive crises are reported in up to 30% of patients. Recurrence risk after complete resection is 5-10% for sporadic tumors but rises to 20-30% in hereditary syndromes, particularly SDHB ^[123]B2a. Partial adrenalectomy , increasingly used for bilateral or hereditary disease, has a pooled recurrence rate of 5.9% and a metastatic rate of 1.5% ^[123]B2a. Central nervous system metastases are rare (<1%) but carry a dismal prognosis, with median survival of 6 months after diagnosis ^[121]C4.

Pearl: The single most important prognostic factor in pheochromocytoma is the presence of an SDHB germline mutation, which mandates lifelong surveillance for metastatic disease; complete surgical resection of localized tumors offers an excellent prognosis with biochemical cure rates exceeding 95% ^{[101]C4[123]B2a}.

Management of pheochromocytoma in special populations requires tailored approaches that account for age-related physiology, pregnancy-related changes, and comorbid conditions.

Pediatrics

Pediatric pheochromocytoma is rare and frequently hereditary, with germline mutations in SDHB, VHL, RET, or NF1 identified in up to 80% of cases ^[20]B2b. Presentation often mimics essential hypertension , delaying diagnosis. Preoperative α-blockade with phenoxybenzamine (0.2-1 mg/kg/day) is standard, with β-blockade added after adequate α-blockade to control tachycardia. Surgical resection is curative, but lifelong surveillance for recurrence and metachronous tumors is essential due to high genetic penetrance ^[20]B2b. Prognosis is excellent for localized disease.

Pregnancy

Pheochromocytoma in pregnancy poses diagnostic challenges because symptoms (palpitations, sweating, hypertension) overlap with preeclampsia and gestational hypertension ^[45]D5. Diagnosis relies on plasma or urinary metanephrines; MRI without gadolinium is the imaging modality of choice. Medical management with α-blockade (phenoxybenzamine 10-20 mg twice daily, titrated) is the cornerstone; β-blockade (propranolol 20-40 mg three times daily) is added if needed. Surgery is reserved for the first or early second trimester; otherwise, resection is deferred until postpartum ^[45]D5. Delivery planning involves a multidisciplinary team; elective cesarean section under combined epidural-general anesthesia is preferred to avoid catecholamine surges during labor. Breastfeeding is generally safe with α-blockers, but infant monitoring for hypotension is advised.

Elderly

Older patients (>50 years) with pheochromocytoma present more often with incidental adrenal masses and less frequently with classic paroxysmal symptoms ^[126]B3b. They have a lower prevalence of germline mutations and a higher proportion of noradrenergic tumors ^[126]B3b. Diagnostic workup must account for false-positive metanephrines due to comorbidities (e.g., renal impairment, heart failure) and medications (e.g., tricyclic antidepressants) ^[47]B2b. Preoperative α-blockade should be initiated at lower doses (phenoxybenzamine 10 mg twice daily) and titrated slowly to avoid orthostatic hypotension. Intraoperative hemodynamic instability is more common in older patients, necessitating close monitoring ^[126]B3b. Prognosis is similar to younger patients for localized disease, but perioperative morbidity is higher.

Immunocompromised

Data on pheochromocytoma in immunocompromised patients are limited. Management follows standard principles, but perioperative infection risk is elevated, requiring prophylactic antibiotics and careful wound care. Drug interactions with immunosuppressants (e.g., calcineurin inhibitors) and α-blockers should be monitored. Preoperative optimization of immune function is advisable when possible.

Pearl: In pregnancy, pheochromocytoma is a high-risk condition requiring multidisciplinary management with α-blockade and planned cesarean delivery; in elderly patients, lower α-blocker starting doses and vigilance for false-positive metanephrines are critical ^{[45]D5[126]B3b}.