Extraadrenal Pheochromocytoma: MRI

Fig. 1: Axial T2-weighted MR image with fat suppression shows a well circumscribed retroperitoneal soft tissue mass below the aortic bifurcation with heterogeneous high T2 signal intensity.
Fig. 2: Post contrast MR image shows heterogeneous enhancement of the mass.

Facts: Extraadrenal Pheochromocytoma

• 10% of all pheochromocytoma
• Most in the abdomen (98%)
• Along prevertebral and paravertebral ganglia, including the organ of Zuckerkandl (which is the only macroscopic extraadrenal sympathetic paraganglia located at the origin of inferior mesenteric artery)
• Benign or malignant difficult to determine by histology. If there is local invasion or metastasis to non-chromaffin tissues --> malignant
• Extraadrenal pheochromocytoma metastasizes more often than adrenal counterpart

MR Imaging Appearance

• High T2 signal intensity, classic "salt-and-pepper" pattern on T2WI
• Enhancing, usually heterogeneous
• No lipid content (lack of signal dropout on opposed-phase images)

Our case - extraadrenal pheochromocytoma below the aortic bifurcation incidentally found on MRI, confirmed with I-123 MIBG and serum catecholamines. It should be noted that half of all pheochromocytomas are now discovered incidentally on imaging.

Reference:

Elsayes KM, Narra VR, Leyendecker JR, et al. MRI of adrenal and extraadrenal pheochromocytoma. AJR 2005;184:860-867.

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