April 21, 2010

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.

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

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