Figures 1 and 2: Axial in and out of phase images demonstrate a large well defined mass (6.2 x 5.3
cm) in the left adrenal gland which abuts the left crus, the kidney and the pancreas
without evidence of invasion. The splenic vein is draped over the anterior portion of the mass and there is no vascular invasion. This adrenal mass does not demonstrate drop-out signal in the out of phase image (Figure 2).

Figure 3: Coronal HASTE image demonstrates that the adrenal mass is mildly heterogeneous in
signal intensity and contains areas of T2 hyperintensity.

Figure 4: Axial contrast enhanced image demonstrates that the adrenal mass has a heterogeneous
enhancement pattern and contains areas of hypervascularity.

Pheochromocytoma.

Pheochromocytomas are rare cateholamine producing neoplasms most commonly found in the adrenal medulla (90%). Most tumors are unilateral and frequently greater than 3 cm in diameter at presentation. Pheochormocytomas are extra-adrenal or bilateral 10% of the time. Extra-adrenal sites include the retroperitoneal ganglia, organ of Zuckerkandl, urinary bladder, chest, skull base, vagina, anus, and spermatic cord. Ten percent of pheochromocytomas are malignant, with metastatic spread occurring most commonly to lymph nodes, bone, and liver. Extra-adrenal origin tumors are malignant in a greater percentage of cases (40%). Although most commonly sporadic, approximately 10% of pheochromocytomas are associated with other syndromes including multiple endocrine neoplasia (MEN) type II, von Hippel-Lindau disease, and neurofibromatosis. Multiple pheochromocytomas are more often associated with syndromic lesions.

Pheochromocytomas occur at all ages but are more common in the fourth through the sixth decades of life. Women and men are equally affected. Patient presentation can be variable, with most patients presenting with hypertensive crisis, proxsymal symptoms suggestive of seizure disorder, anxiety attacks (palpitations, headache, nausea, sweating), or essential hypertension that responds poorly to conventional treatment. Hypertension may be sustained or paroxysmal and the hypertensive episodes can be severe or malignant and respond poorly to standard treatments for essential hypertension. Even though hypertension is one of the hallmark clinical findings (detected in 61-100% of patients), pheochromocytoma accounts for the cause of hypertension in less than 1% of patients. A great majority of symptomatic patients have elevated levels of urinary catecholamines and their metabolites, principally vanillylmandelic acid (VMA) and metanephrine. Entities that can present with signs and symptoms similar to those displayed by patients with pheochromocytoma include essential hypertension, renovascular hypertension, hypertension of pregnancy, anxiety attacks, pressor crises associated with the withdrawal of some antihypertensive agents, self-administration of sympathomimetic amines, intracranial tumors, and epilepsy.

The MR appearance of pheochromocytoma has classically been described as markedly hyperintense (“light bulbs”) on T2-weighted images. However, the majority of pheochromocytomas demonstrate variable signal on T2-weighted sequences, especially when they are greater than 5 cm in size. These lesions can have heterogeneous and moderately high signal intensity, and rarely, moderate signal intensity. On T1-weighted images, pheochromocytomas characteristically are hypointense. The imaging characteristics of pheochromocytoma on T1- and T2-weighted images reflects the large interstitial fluid space component of these lesions and in part may reflect necrotic, hemorrhagic, or cystic areas. Pheochromocytomas generally enhance minimally on immediate post-gadolinium images and demonstrate progressive enhancement of later interstitial phase images. However, early intense enhancement of these lesions can also be seen. In general, pheochromocytomas do not lose signal intensity on out-of-phase images. MR imaging is also useful in identifying extra-adrenal pheochromocytomas (paragangliomas) and detecting recurrences after resection, given their increased signal intensity on T2-weighted images. Our MR imaging findings for pheochromocytoma are not pathognomonic and in the absence of patient history, the differential for an adrenal mass includes: lipid-poor adenoma, metastatic carcinoma from an unknown primary malignancy, adrenal cortical carcinoma, and adrenal lymphoma.

References:

1. Semelka, Richard. Abdominal-Pelvic MRI. New York: Wiley-Liss Inc, 2002. pp. 728-730.
2. Israel GM and GA Krinsky. MR Imaging of the Kidneys and Adrenal Glands. Radiologic Clinics of North America. 2003; 41: 145-159.
3. Lockhart ME, Smith JK, and PJ Kenney. Imaging of Adrenal Masses. European Journal of Radiology. 2002; 41: 95-112.
4. Mayo-Smith WW, Boland GW, et al. From the RSNA Refresher Courses: State-of-the-Art Adrenal Imaging. RadioGraphics. 2001; 21: 995-1012.
5. Walther MM, Keiser HR, and WM Linehan. Pheochromocytoma: Evaluation, Diagnosis, and Treatment. World Journal of Urology. 1999; 17: 35-39.