Bilateral Pheochromocytoma- a Diagnostic Dilemma

Clinical History

A 24-year-old male patient presented with complaints of abdominal pain since 6 months.

Upon examination, the blood pressure recorded was 210/110 mm Hg.

Imaging Findings

A 16 slice plain CT showed large (>5cm), well defined heterogeneous lesions in the bilateral adrenal gland region with few calcifications on the left side. Adrenal glands were not separately visualized from the lesions on both sides. Both the lesions were showing 10-40 HU value. On contrast administration, both lesions showed peripheral thick irregular rim of arterial and early venous phase enhancement, more on early venous phase with HU value of 165-203 on right side and 163-195 on left side and a central non-enhancing area representing necrosis/ cystic area. There is complete washout of lesions on delayed phases (20min). The absolute and relative washout values of 74% and 58.3% on the right and 73% & 56.3% on left side respectively. Multiple small simple cysts were seen in the pancreas.
Plain MRI showed predominantly hyperintense lesions in the bilateral adrenal gland on T2 WIs. No loss of signal intensity was noted in out of phase images.

Discussion

Pheochromocytomas are a type of paragangliomas produced from chromaffin cells.
They present with hypertension and/or cardiac arrhythmia. They can be clinically silent when they grow to a larger size. Imaging is usually required for localization, characterization and staging of the adrenal lesion and also to identify extra-adrenal pheochromocytomas. A major importance lies in the noninvasive diagnosis of pheochromocytomas as any physical contact with these tumours can precipitate cardiac arrhythmia and malignant hypertension. Laboratory findings include elevated plasma metanephrines and increased catecholamines [1]. Most of these are located in the adrenal gland (pheochromocytoma) and a few in an extra adrenal location. A diagnostic dilemma arises due to varied imaging features noted in this tumour.

Ultrasonographic imaging features have a variable appearance ranging from solid to mixed cystic and solid lesions with necrotic/hemorrhagic components [2]. Acute haemorrhage in a pheochromocytoma may appear echogenic.

On computed tomography, pheochromocytomas may be homogeneous or heterogeneous, solid or cystic complex masses with attenuation higher than 10 HU. Few may show calcification. They enhance avidly but can be heterogeneous or show regions of no enhancement due to cystic changes/necrosis. They also tend to enhance more on the early venous phase than the arterial phase with contrast wash out similar to an adrenal adenoma, with absolute and relative contrast washout of >60% and 40%. [1, 3, 4].
On MR imaging, pheochromocytoma appears hypo-intense on T1WIs and intensely hyper-intense on T2-weighted imaging, classically described as light bulb sign. These lesions enhance avidly with gadolinium-based contrast material, however signal and enhancement pattern may vary according to the presence of fat, haemorrhage, cystic changes and necrosis [2].

I-123 Metaidobenzyl guanidine uptake noted in an adrenal nodule is highly suggestive of pheochromocytoma [2]. Dopamine positron emission tomography is also sensitive in detecting extra-adrenal pheochromocytoma.
Features that differentiate pheochromocytoma from adrenal carcinoma are well-defined, regular borders with no evidence of adjacent infiltration, no lymph nodal involvement and absolute and relative contrast washout of >60% and 40%. Though the contrast washout pattern was similar to adenoma, the larger size of the lesion, attenuation >10HU on plain CT and >125 HU value on early venous phase, heterogeneous contrast enhancement on CECT and absence of signal loss in out of phase images on MRI, helped to rule out the possibility of adrenal adenoma.

Differential Diagnosis List

Final Diagnosis

Bilateral pheochromocytoma and to rule out Von hippel lindau syndrome

URL:	https://www.eurorad.org/case/14203
DOI:	10.1594/EURORAD/CASE.14203
ISSN:	1563-4086