What imaging modalities are recommended to investigate a possible pheochromocytoma?

Imaging for Suspected Pheochromocytoma

For suspected pheochromocytoma after biochemical confirmation, start with CT or MRI of the abdomen and pelvis, then proceed to 123I-MIBG scintigraphy for sporadic cases, reserving advanced PET imaging for MIBG-negative cases, hereditary syndromes, or metastatic disease. 1

Initial Anatomical Imaging

CT or MRI of the abdomen and pelvis should be performed first after biochemical diagnosis is established. 2, 3, 4

• CT without contrast is preferred to avoid the risk of hypertensive crisis from IV contrast administration. 5, 2
• MRI offers superior soft tissue contrast and is particularly useful when CT contrast is contraindicated or for detecting lesions missed on CT. 2
• Both modalities should image from the diaphragm through the pelvis to capture adrenal and extra-adrenal locations. 1

When Initial Imaging is Negative

If abdomen/pelvis imaging is negative but biochemical evidence remains positive, extend imaging to include the chest and neck to search for extra-adrenal paragangliomas. 2, 6

• Paragangliomas can occur in atypical locations including the thorax, head and neck regions, and other sites not covered by standard abdominal imaging. 1, 2

Functional Imaging Strategy

For Apparently Sporadic Non-Metastatic Pheochromocytoma

123I-MIBG scintigraphy is the first-line functional imaging modality. 1

• MIBG has sensitivity equal to PET imaging for localizing non-metastatic sporadic pheochromocytoma. 1
• It provides whole-body screening to rule out extraadrenal disease and guide additional anatomical imaging. 1
• Reserve PET tracers for MIBG-negative cases, multifocal tumors on MIBG, or patients taking drugs that interfere with MIBG accuracy. 1

For Head and Neck Paragangliomas

18F-FDOPA PET is the most sensitive imaging tool with sensitivity approaching 100%. 1

• If 18F-FDOPA is unavailable, use SSTR scintigraphy with 111In-pentetreotide SPECT/CT as first-line evaluation. 1
• 68Ga-conjugated peptide SST analogues show high sensitivity and are increasingly available. 1
• 123I-MIBG and 18F-FDA PET are not sufficiently sensitive for head and neck paragangliomas. 1

For Metastatic or Hereditary Disease

The choice of functional imaging depends on genetic status: 1

• SDHB-related metastatic disease: 18F-FDG PET is the imaging modality of choice. 1
• Non-SDHB metastatic disease or unknown genetic status: 18F-FDOPA PET/CT is preferred. 1
• 18F-FDA PET has the highest sensitivity and specificity across all genetic subtypes but suffers from limited availability (currently only at NIH). 1
• 123I-MIBG alone significantly underestimates metastatic disease and should not be used as the sole modality. 1

For MEN2-Related Pheochromocytoma

Many patients do not need functional imaging if the tumor is confined to the adrenal gland with characteristic metanephrine elevation. 1

• If functional imaging is needed, 18F-FDOPA PET is useful due to absent uptake in normal adrenal glands. 1
• 123I-MIBG has suboptimal sensitivity and specificity in this setting. 1
• 18F-FDG PET is not sufficiently sensitive for MEN2-related disease. 1

Imaging Algorithm Summary

1. Confirm biochemical diagnosis first with plasma free metanephrines or 24-hour urinary fractionated metanephrines. 2, 6
2. Perform CT (unenhanced) or MRI of abdomen and pelvis as initial localization. 2, 3, 5
3. If negative, extend to chest and neck imaging. 2, 6
4. Add functional imaging based on clinical scenario:
   • Sporadic non-metastatic: 123I-MIBG scintigraphy 1
   • Head/neck paraganglioma: 18F-FDOPA PET 1
   • SDHB-related metastatic: 18F-FDG PET 1
   • Other metastatic/unknown genetics: 18F-FDOPA PET 1
5. Consider SPECT/CT or PET/CT hybrid imaging to improve diagnostic accuracy by combining anatomical and functional data. 1, 2

Critical Pitfalls to Avoid

• Never perform fine needle biopsy of suspected pheochromocytoma due to risk of hypertensive crisis. 2, 6
• Do not rely solely on CT imaging without biochemical confirmation. 2
• Do not fail to consider extra-adrenal locations when adrenal imaging is negative. 2, 6
• Do not use 123I-MIBG as the sole imaging modality for metastatic disease as it significantly underestimates disease burden. 1
• Avoid IV contrast CT when possible due to risk of precipitating hypertensive crisis. 5, 2
• Do not overlook the need to image from skull base to pelvis when searching for paragangliomas, as they can occur in atypical locations. 1