OBJECTIVETo evaluate the CT and MR findings of retroperitoneal ectopic pheochromocytoma.

METHODSTo analyze retrospectively the CT and MR images of 32 patients with retroperitoneal ectopic pheochromocytoma proved by pathology.

RESULTSThe lesions (benign=28, malignant=4) were located in the anterior pararenal space (ARS) (n=12), the perirenal space (PS) (n=13) and the posterior pararenal space (PRS) (n=7). The tumors showed heterogeneous density on unenhanced CT (n=25). Among the 23 cases with enhanced CT imaging, 19 cases had marked contrast and 4 had mild contrast. The enhancement patterns included whole enhancement (n=9), solid area enhancement (n=12), peripheral enhancement (n=1), and spotted enhancement (n=1). The tumors had heterogeneous signal on unenhanced MR (n=23), and usually showed enhancement at arterial, portal and delayed phases on 22 enhanced MR, while cystic area with no enhancement. The lesions usually had cystic changes (n=18), septa (n=16), vessels inside (n=9), hemorrhage (n=3), and calcification (n=3). Besides that the morphology had statistical significance (P=0.013), other indexes had no statistical significance (P>0.05) in differential diagnosis of benign and malignant retroperitoneal ectopic pheochromocytomas.

CONCLUSIONSRetroperitoneal ectopic pheochromocytomas have some CT and MR features, usually revealed as an oval mass, growing along the paravertebral axis, and often with cystic changes. Those signs combined with hypertension and elevated catecholamine level may lead to a correct diagnosis.