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KEY FACTS

Terminology
- Tumor arising from chromaffin cells of adrenal medulla or extraadrenal paraganglia
Imaging
- Adrenal medulla (90%)
- Extraadrenal (10%) - Along sympathetic chain: Anywhere from neck to urinary bladder - Subdiaphragmatic (98%) or thoracic (1-2%) - Organ of Zuckerkandl and near urinary bladder are relatively common sites
- Hereditary pheochromocytomas - Small, bilateral adrenal lesions in younger patient
- Sporadic pheochromocytoma - Large (> 3 cm), unilateral adrenal mass in older patients
- US: Hypoechoic suprarenal lesion ± cystic change - Cystic components may be identified
- NECT: > 10 HU
- CECT: Heterogeneous enhancement - Delayed washout kinetics typically similar to adrenal carcinoma and metastases, but rapid washout (like adenoma) possible - Heterogeneous enhancement: Necrosis, cystic degeneration, and hemorrhage
- MR - Variable T1/T2 signal due to hemorrhage, cystic degeneration, and necrosis - Traditional classic imaging feature: T2 ("light bulb") hyperintensity - Hypervascular solid components
- Ga-68 DOTATATE: Ectopic, recurrent, and metastatic tumors
Pathology
- Autosomal dominant familial syndromes - von Hippel-Lindau, multiple endocrine neoplasia 2, neurofibromatosis type 1
Diagnostic Checklist
- Pheochromocytoma is not distinguished from other tumors by imaging appearance alone - Clinical history and lab values are necessary for diagnosis - Urinary and plasma fractionated metanephrines and catecholamines

TERMINOLOGY

Definitions
- Tumor arising from chromaffin cells of adrenal medulla or sympathetic nervous system - Extraadrenal pheochromocytoma: Paraganglioma, ganglioneuroma

IMAGING

General Features
- Best diagnostic clue
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- Adrenal mass with appropriate clinical history and supporting biochemical studies (elevated catecholamines)
- Characteristic T2 hyperintensity described in very early literature, though imaging appearance varies at MR (and other modalities)
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- Location
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- Adrenal medulla (90%) or extraadrenal (10%)
- Extraadrenal, along sympathetic chain: Neck to urinary bladder
        - Subdiaphragmatic (98%) or thoracic (1-2%)
        - Organ of Zuckerkandl and near bladder are relatively common sites
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- Size
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- Usually larger (> 3 cm) in sporadic (nonsyndromic) or clinically silent cases
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- Morphology
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- Well-circumscribed, encapsulated tumor
        - Solitary (sporadic) or multiple (familial)
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- Key concepts - Classic teaching: Rule of 10s (or 10% tumor) - 10% extraadrenal (paraganglioma) - 10% bilateral - 10% malignant - 10% extraabdominal - 10% familial - 10% pediatric - 10% silent - 10% autosomal dominant transmission - Demographics evolving - ↑ detection of incidental, clinically silent adrenal lesions (including pheochromocytoma) on CT - Large imaging series: 23-58% of pheochromocytomas clinically occult - Prompts aggressive biochemical evaluation of incidental adrenal lesion - Larger percentage of syndromic tumors likely: More aggressive screening for predisposing hereditary conditions - Multiple endocrine neoplasia 2 (MEN2), von Hippel-Lindau (VHL) - Neuroectodermal disorders: Neurofibromatosis type 1 (NF1), Sturge-Weber syndrome, Carney triad - 25% of patients with apparent sporadic pheochromocytomas are carriers of gene mutations - Extraadrenal tumors arise from sympathetic ganglia - Neck, mediastinum, pelvis, or urinary bladder - Aortic bifurcation (organ of Zuckerkandl): Ganglia at origin of inferior mesenteric artery - Imaging: Difficult to distinguish benign from malignant - Distant metastases indicate malignancy

CT Findings

NECT

- Attenuation ranges from low density to soft tissue attenuation
- Attenuation almost always > 10 HU and usually ≥ 40 HU, though rare intracellular lipid-containing pheochromocytomas reported
- ± areas of ↑ density (hemorrhage)
- ± areas of ↓ density (cystic degeneration, necrosis)
- ± areas of curvilinear or mural calcification

CECT

- Heterogeneous enhancement due to tissue necrosis, cystic degeneration, and hemorrhage
        - Modified criteria: 1 min ≥ 160 HU; 15 min ≥ 70 HU; or intralesional cystic degeneration at both 1 min and 15 min
- Solid components briskly enhance
        - Hyperenhancement (> 110 HU) on late arterial phase may suggest pheochromocytoma
        - Early, marked enhancement also possible with vascular metastases (hepatocellular carcinoma, renal cell carcinoma)
- Initial literature suggested pheochromocytoma washout characteristics similar to adrenal carcinoma and metastases 
        - Recent work suggests large percentage of pheochromocytomas with washout percentages similar to adenomas
- Theoretical risk of induction of hyperadrenergic symptoms with iodinated contrast administration discounted by retrospective series utilizing nonionic material

MR Findings

T1WI

- Isointense to muscle and hypointense to liver
- Heterogeneous signal
        - Due to areas of hemorrhage and necrosis
- ± areas of ↑ signal
        - Due to acute or subacute hemorrhage

T2WI

- T2 heterogeneity typical
        - Due to ↑ water content as result of necrosis, cystic degeneration
        - Markedly hyperintense ("light bulb") characteristic in early MR series, later discounted
        - ↓ T2 signal does not exclude pheochromocytoma

DWI

- Unlike lesion size, ADC values generally not useful for differentiating benign vs. malignant

T1WI C+

- Characteristic salt and pepper pattern (due to ↑ tumor vascularity)
        - Salt: Represents enhancing parenchyma
        - Pepper: Represents flow void of vessels
- Can show marked early as well as prolonged contrast enhancement

Ultrasonographic Findings

Grayscale ultrasound

- Variable echogenicity: Majority iso- to hypoechoic
        - Intralesional hemorrhage may be echogenic
- Round and well-circumscribed mass
- Cystic components may be identified
- Malignant features include large size, irregular shape, poorly defined margins, heterogeneity, and hypervascularity
        - 75% of malignant pheochromocytomas are hypoechoic; 20% show mixed echogenicity and cystic necrosis

Angiographic Findings
- Conventional - Hypervascular tumor
Nuclear Medicine Findings
- I-131 or I-123 MIBG - Most common and available technique - MIBG is norepinephrine analogue: Uptake proportional to number of neurosecretory granules within lesion - I-123 MIBG has largely replaced I-131 MIBG (lower radiation dose, improved image quality) - I-123 MIBG sensitivity: 77-90%; specificity: 95-100% - Hybridized MIBG SPECT/CT improves diagnostic accuracy - Particularly useful for extraadrenal paraganglioma detection, malignant pheochromocytoma staging
- In-111 pentetreotide (somatostatin analog): Potentially useful for dedifferentiated pheochromocytoma
- PET - Ga-68 DOTATATE: Largely replaced MIBG as primary imaging modality - Neuroendocrine tumors express somatostatin receptors - F-18: Can be utilized in imaging of faster-growing pheochromocytomas
Imaging Recommendations
- Helical NE + CECT - Hypertensive crises not documented with IV administration of nonionic contrast material - Routine premedication (α and β blockade) isnot recommended
- MR ± contrast
- Ga-68 DOTATATE PET/CT - For ectopic, recurrent, and metastatic tumors

DIFFERENTIAL DIAGNOSIS

Adrenal Adenoma
- NECT: Well-defined mass < 10 HU (lipid rich)
- CECT: Enhancing mass that washes out rapidly - Early hyperenhancement and marked wash out of pheochromocytomas are reported and may mimic adenomas
- Adenoma with hemorrhage or necrosis may resemble pheochromocytoma
Adrenal Carcinoma
- Rare; usually unilateral
- Large, unilateral adrenal mass with invasive margins - ± calcification (30% of cases); variable enhancement - Metastatic tumor spread: Lungs, liver, nodes, and bone - Inferior vena cava tumor thrombus
Adrenal Metastases and Lymphoma
- Adrenal metastases - e.g., lung, breast, renal cell carcinoma, and melanoma - Unilateral or bilateral; central necrosis ± hemorrhage - History of primary malignancy
- Adrenal lymphoma - Usually as part of diffuse disease - Rarely limited to adrenals - Non-Hodgkin most common; usually bilateral - CECT: Mild enhancement (hypovascular)
Adrenal Myelolipoma
- Rare benign tumor (fat + hematopoietic elements)
- Unilateral fatty adrenal tumor (-100 to -30 HU)
- T1WI: Typically hyperintense; size varies (2-10 cm)
- Signal loss on T1WI with fat suppression
Adrenal Hemorrhage
- Etiology: Septicemia, burns, trauma, stress, hypotension, and hematological abnormalities
- CT findings - Usually bilateral - Old hemorrhage: Soft tissue attenuation (20-35 HU) - Recent hemorrhage: ↑ attenuation values
- MR findings: T1WI and T2WI - Varied signal depending on hematoma age - Subacute phase: Usually ↑ signal (methemoglobin) - Perilesional dark ring (hemosiderin or ferritin)
Adrenal Tuberculosis and Fungal Infection
- e.g., tuberculosis, histoplasmosis, other fungal diseases
- Usually bilateral, heterogeneous, poorly enhancing (acute)
- Chronic: Small and calcified adrenals
- Diagnosis: Clinical history and lab data

PATHOLOGY

General Features

Etiology

- Chromaffin cells of adrenal medulla or extraadrenal paraganglioma
        - Adrenal medulla: Pheochromocytoma
        - Extraadrenal: Paraganglioma

Associated abnormalities

- Classic associated syndromes
        - VHL syndrome
                  - Pheochromocytoma may be only manifestation of VHL or occur along with other tumors
        - NF1
        - MEN syndromes types 2A and 2B
        - Tuberous sclerosis; Sturge-Weber syndrome
        - Carney triad
                  - Functional extraadrenal paraganglioma, pulmonary chondroma, gastric leiomyosarcoma
- Adage that only 10% of pheochromocytomas are hereditary discounted with recent advances in molecular studies
- 25% of patients with previously considered sporadic pheochromocytomas are carriers of gene mutations

Embryology/anatomy - Neoplasm of chromaffin cells derived from neural crest or neuroectoderm

Gross Pathologic & Surgical Features
- Round, tan-pink to violaceous, encapsulated mass
- ± cystic, mucoid, serosanguineous hemorrhage
Microscopic Features
- Large cells: Granular cytoplasm and pleomorphic nuclei
- Chromaffin reaction: Cells stained + chromium salt

CLINICAL ISSUES

Presentation
- Most common signs/symptoms
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- Symptoms may be episodic or paroxysmal
- Crisis: Headaches, hypertension, palpitations, diaphoresis, tremors, arrhythmias, pain
- Classic triad: Headache, palpitations, diaphoresis
        - 90% specific but uncommon presentation (10-36%)
- Atypical: Labile hypertension, myocardial infarction, stroke
- Often clinically silent
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- Clinical profile
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- Young patient with paroxysmal attacks of headache, palpitations, sweating, and tremors
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- Lab data - 24-hour urine-fractionated metanephrine evaluation often initial biochemical test - Excretion of metanephrine, normetanephrine, and 3-methoxytyramine (dopamine metabolite) measured - Sensitivity: 90-97%; specificity: 69-98% - Plasma-fractionated metanephrines also measured, though low positive predictive value and ↓ specificity results in high false-positive rates

Demographics

Age

- Sporadic pheochromocytoma: Older patients (mean: 44 years)
- Hereditary pheochromocytoma: Younger patients (mean: 25 years)
- Pheochromocytomas are exceedingly rare in pediatric patients
        - Higher genetic predisposition and malignancy incidence

Sex
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- F > M
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Epidemiology

- Incidence
        - 0.13% in autopsy series; accounts for 0.1-0.5% of patients with hypertension
        - Prevalence likely underestimated

Natural History & Prognosis
- Complications: During hypertensive crisis - Cerebrovascular accidents - Pregnancy + pheochromocytoma: Mortality (48%) - Malignancy in 2-14% cases
- Prognosis - Noninvasive and nonmetastatic: Good prognosis - Malignant and metastatic: Poor prognosis - 5-year survival rate: < 50%
Treatment
- Medical therapy: Before, during, and after surgery - α-adrenergic blockers - Phenoxybenzamine, phentolamine - β-adrenergic blocker: Propranolol
- Surgical resection: Benign and malignant - Laparoscopic resection preferred - Posterior retroperitoneoscopic adrenalectomy associated with ↓ morbidity compared to transabdominal laparoscopic approach - Partial adrenalectomy may be performed with bilateral pheochromocytomas - Cortical-sparing adrenalectomy in patients with hereditary pheochromocytoma shows survival similar to total adrenalectomy but recurrence in 13%
- HSA I-131 MIBG and tumor debulking for metastatic, unresectable, or locally advanced malignant pheochromocytomas
- Combination chemotherapy: Cyclophosphamide + vincristine + dacarbazine

DIAGNOSTIC CHECKLIST

Consider
- Clinical history, supporting biochemical data ultimately drive diagnosis
Reporting Tips
- CT and MR features (vascularity, cystic change, T2 heterogeneity) may suggest pheochromocytoma, but overlap precludes definitive diagnosis solely by imaging
- Possibility of pheochromocytoma should be raised, but lab analysis confirms or excludes diagnosis

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References

Selected References

Images

Selected Images

Coronal CECT in a 74-year-old man with neurofibromatosis type 1 (NF1) shows a 10-cm, cystic and solid right adrenal mass , surgically proven to be a pheochromocytoma. ~ 1-6% of patients with NF1 develop pheochromocytoma. Note IVC filter .

Axial T2 FS MR in an 80-year-old man with sporadic pheochromocytoma shows a rounded right adrenal mass with heterogeneous signal. Sporadic pheochromocytoma occurs more often in older patients. Note incidental hepatic cyst .

Axial T2 FS MR in a 40-year-old woman with headaches, palpitations, and chronic diaphoresis shows an intermediate-signal, 5-cm left adrenal mass with internal areas of hyperintensity suggesting cystic degeneration or necrosis.

Axial T1 C+ FS MR in the same patient shows heterogeneous enhancement of the left adrenal mass with cystic degeneration or necrosis . Surgical pathology showed pheochromocytoma, which was sporadic in this patient with no family history.

Coronal CECT shows a heterogeneous right adrenal mass in a 51-year-old woman with abdominal pain, headaches, and markedly elevated 24-hour urine metanephrines. The mass was surgically proven to be pheochromocytoma.

Axial CECT in a 44-year-old man with hypertension shows an incidental right adrenal mass following motor vehicle collision. The mass was resected via right posterior retroperitoneoscopic adrenalectomy and pheochromocytoma was confirmed.

Axial T2 FS MR in a 66-year-old woman with ↑ 24-hour metanephrines shows a heterogeneous mass in the hepatorenal space . Heterogeneous T2 signal is often seen due to varying degrees of hemorrhage and necrosis.

Axial T1 FS C+ MR in the same patient shows heterogeneous enhancement of the surgically proven pheochromocytoma . The patient was treated with alpha-blockade (phenoxybenzamine) for 1 month prior to intervention.

Axial CECT in a 79-year-old man with locally recurrent pheochromocytoma shows an irregular, enhancing mass in the left adrenal fossa abutting the anterior left kidney . Note incidental chronic aortic dissection .

Axial Ga-68 DOTATATE PET/CT in the same patient shows avid tracer uptake in the left adrenal fossa , corresponding to the enhancing mass on CT and consistent with locally recurrent pheochromocytoma.

Axial CECT shows bilateral, centrally necrotic adrenal masses in a 10 year old with von Hippel-Lindau (VHL) syndrome and pheochromocytomas. Cortical-sparing adrenalectomy was performed on the left mass. Up to 30% of patients with VHL develop pheochromocytoma.

Axial Cu-61 DOTATATE PET/CT in the same patient shows minimal peripheral uptake by the bilateral adrenal masses due to extensive necrosis. Note physiologic uptake in the left kidney .

Axial T2 FS MR in a 21-year-old man with neurofibromatosis type 1 (NF1) shows a heterogeneous right adrenal mass proven to be pheochromocytoma. While classically described as "light bulb bright," the T2 signal of this neoplasm is highly variable.

Axial CECT shows a heterogeneously enhancing right adrenal mass in a 55-year-old man with elevated 24-hour urine metanephrine and pheochromocytoma shown at surgical pathology.

Transverse US of the RUQ for pleuritic chest pain in a 20-year-old man shows a round mass posterior to the right hepatic lobe with centrally decreased echogenicity suggesting necrosis.

Axial CECT in the same patient shows a centrally necrotic right adrenal mass , surgically proven pheochromocytoma. Multiple pancreatic cysts are also noted, and the diagnosis of familial VHL syndrome was subsequently confirmed.

Additional Images

Axial I-123 MIBG SPECT/CT in a 79-year-old man with locally recurrent pheochromocytoma shows avid tracer uptake in the left adrenal fossa extending to the perisplenic space , consistent with recurrent pheochromocytoma.

Axial CECT in a 36-year-old woman shows a 7-cm, heterogeneous left adrenal mass . The differential includes adrenal carcinoma, pheochromocytoma, and metastasis. Urinary metanephrines were ↑, and laparoscopic resection (after α and β blockade) confirmed hemorrhagic pheochromocytoma.

Axial T2 MR in the same patient shows a hyperintense ("light bulb") left adrenal lesion . Although this appearance was historically thought to be characteristic of pheochromocytoma, it is neither sensitive nor specific. Elevated 24-hour urine metanephrines confirmed pheochromocytoma in this case.

Axial T1 C+ MR in a 52-year-old woman to evaluate an incidental adrenal lesion previously identified on CT shows a 2-cm, vascular left adrenal mass .

Axial T2 MR in the same patient shows a slightly intense right adrenal lesion and adjacent renal/hepatic cysts . Elevated 24-hour urinary metanephrines indicated (sporadic) unilateral pheochromocytoma, although the imaging appearance is nonspecific.

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KEY FACTS

Terminology

Imaging

Pathology

Diagnostic Checklist

TERMINOLOGY

Definitions

IMAGING

General Features

Best diagnostic clue

Location

Size

Morphology

CT Findings

NECT

CECT

MR Findings

T1WI

T2WI

DWI

T1WI C+

Ultrasonographic Findings

Grayscale ultrasound

Angiographic Findings

Nuclear Medicine Findings

Imaging Recommendations

DIFFERENTIAL DIAGNOSIS

PATHOLOGY

General Features

Etiology

Associated abnormalities

Gross Pathologic & Surgical Features

Microscopic Features

CLINICAL ISSUES

Presentation

Most common signs/symptoms

Clinical profile

Demographics

Age

Sex

Epidemiology

Natural History & Prognosis

Treatment

DIAGNOSTIC CHECKLIST

Consider

Reporting Tips

References

Selected References

Images

Selected Images

Additional Images

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