Paediatric extraadrenal pheochromocytoma

Clinical History

In a 12-year-old girl who consulted for obesity, physical examination revealed hypertension (160/110) with no associated symptoms. Further controls showed abnormal thyroid hormones with elevation of TSH, and elevated 24-hour urinary catecholamine levels (4-fold elevation of noradrenalin).

Imaging Findings

An abdominal ultrasound was performed and showed a 3-cm round, retroperitoneal, well circumscribed mass, which was mildly hyperechogenic with no evident involvement of the adrenal glands (Fig. 1).
On the MRI that followed, the lesion appeared isointense on T1-weighted images (Fig. 2), and hyperintense and heterogeneous in T2-weighted images. Furthermore, MRI showed restriction of the diffusion, and heterogeneous enhancement after injection of gadolinium-based contrast material, suggesting a paraganglioma. There were no signs of adjacent vascular involvement.
On MIBG scintigraphy the lesion showed no uptake of radiotracer. The PET/CT 18F-DOPA that was performed afterwards showed radiotracer uptake in the lesion compatible with a paraganglioma, with no other lesion suspicious of metastasis (Fig. 3).
Surgical resection was performed and histology confirmed the diagnosis of benign paraganglioma.
One month post surgery, the clinical control and the catecholamine levels were normal and the follow-up by MRI showed no recurrence.

Discussion

Pheochromocytomas are rare catecholamine-secreting neuroendocrine tumors that arise from the chromaffin cells of the adrenal medulla, or the extra-adrenal sympathetic and parasympathetic paraganglia, in the latter case referred to as paragangliomas (PGL). The most common location for sympathetic paragangliomas is the abdomen, mostly near the renal vessels or the organ of Zuckerkandl, and for parasympathetic paragangliomas the head and neck region [1]. In children, the incidence of extra-adrenal localisation varies between 8-43% [3].
The majority (88%) of pheochromocytomas and paragangliomas are benign [5]. In case of malignancy, local tumour invasion and/or distant metastases are present [3].
The clinical presentation in children may be variable. In most cases the symptoms are a result of the production of catecholamines, such as palpitations, headache, and sweatiness [2]. In children, non-specific symptoms like nausea, vomiting or anxiety are reported more often than in adults [3].
The diagnostic tests recommended by the Task Force of the Endocrine Society include the measurement of fractionated urine metanephrines (metanephrines and normetaneprhines) and plasma free metanephrines. All positive results should be further investigated by an imaging study [4]. Moreover, a genetic test should be performed, as nearly 40% of pheochromocytomas in children have a genetic origin [3, 4].
The imaging of choice for children is MRI, because of the lack of exposure to radiation [4]. As the majority of PGL is found in the abdomen, an MRI of the abdomen and the pelvis should be performed initially [3]. If the result is not conclusive, the diagnosis could be confirmed by a 123-metaiodobenzylguanidine (MIBG) scintigraphy [4]. On MRI, PGLs are hyperintense on T2-weighted sequences, isointense to muscle on T1-weighted series and show enhancement after gadolinium-based contrast injection. The presence of cystic or necrotic areas alters these classic imaging features [2].
The treatment of choice for paragangliomas is the open surgical resection. In the case of easily accessible paragangliomas, a laparoscopic resection could also be considered [4].
The prognosis depends on the presence, or not, of distant metastases and their location [1].
A long-term follow-up with annual biochemical screening and imaging is required to detect any recurrences or metastases [1].

Differential Diagnosis List

Final Diagnosis

Pediatric retroperitoneal paraganglioma

URL:	https://eurorad.org/case/14686
DOI:	10.1594/EURORAD/CASE.14686
ISSN:	1563-4086