Imaging of Pheochromocytoma

In this video lecture, we discuss the diagnosis and imaging appearance of pheochromocytoma on ultrasound, CT, MRI, and nuclear medicine studies.

Key points include:
1) Pheochromocytoma is a biochemical diagnosis.
2) Symptoms are variable, and patients may present with headache, palpitations, sweating, hypertension or be asymptomatic.
3) Most cases are sporadic with mean age of presentation in the 40s.
4) Hereditary pheochromocytoma can be seen in the setting of Von Hippel-Lindau disease, multiple endocrine neoplasia (MEN) type II, neurofibromatosis type I, and pheochromocytoma-paraganglioma syndromes associated with succinate dehydrogenase gene mutations.
5) Pheochromocytoma is the “10%” tumor, as approximately 10% are bilateral, extra-adrenal, contain calcification, occur in children, or are malignant.
6) Most pheochromocytomas are solid, but they can also appear as mixed cystic and solid with varying degrees of complexity.
7) The ultrasound appearance is nonspecific, and tumors may contain echogenic hemorrhage or be hypervascular on Doppler imaging.
8) Any mass that enhances to a density greater than 110 HU on an arterial phase CT scan should raise suspicion for pheochromocytoma.
9) On CT, most pheochromocytomas will have noncontrast density greater than 10 HU and absolute washout less than 60%, findings similar to adrenal metastases and adrenocortical carcinoma.
10) However, pheochromocytoma can rarely have noncontrast density less than 10 HU and absolute washout greater than 60%, thus mimicking adrenal adenoma.
11) Studies have shown that pheochromocytoma is not a contraindication to modern nonionic IV contrast media.
12) On MRI, the “light bulb” T2 bright appearance classically associated with pheochromocytoma may or may not be present.
13) If intratumoral hemorrhage is present, pheochromocytomas may show T1 hyperintensity or susceptibility artifact on T1-weighted in-phase images depending on the age of blood.
14) Pheochromocytomas usually do not show signal dropout on T1-weighted opposed-phase images but rarely do and can mimic adrenal adenomas.
15) MIBG scans have nearly 100% specificity for pheochromocytoma and are useful to confirm clinically suspected pheochromocytoma and for detection of metastatic disease.
16) Extra-adrenal pheochromocytomas (paragangliomas) usually occur in abdomen, typically at the organ of Zuckerkandl or in the retroperitoneum.

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