Clinical History
Chest and abdominal X-ray were performed in a 31-year-old-woman with no relevant medical history in a routine medical check up. The radiological study revealed a large mass located in the upper abdomen.
She was admitted at our hospital to characterise the incidentally discovered mass.
Imaging Findings
An abdominal CT detected a well-defined, oval, hypodense, homogeneous mass in the retroperitoneum with extension into the posterior mediastinum. The lesion presented thin calcifications inside and a slight enhancement after administration of intravenous contrast medium and showed involvement of the great vessels with no luminal narrowing (Fig. 1).
On delayed phase of the abdominal CT, the mass demonstrated a little heterogeneous increase of contrast enhancement (Fig. 2).
Discussion
Abdominal neurogenic retroperitoneal tumours, although rare, must be taken into consideration in the differential diagnosis of retro-peritoneal masses. These infrequent tumours can be classified in three groups: Ganglion cell origin (ganglioneuromas, ganglioneuroblastomas, neuroblastomas), para-ganglionic system origin (pheochromocytomas, paragangliomas), or nerve sheath origin (neurilemmomas, neurofibromas, neurofibromatosis, malignant nerve sheath tumours).
Ganglioneuroma is a rare benign neoplasm which arises from the sympathetic ganglia. The most common locations for a ganglioneuroma are the retro-peritoneum (32%–52% of cases) and posterior mediastinum (39%–43%), followed by the cervical region (8%–9%) [1]. Histological studies show that they are conformed of mature Schwann cells, neuroganglions and nerve fibres with variable amount of myxoid stroma.
They are usually asymptomatic, and they are often discovered when an imaging procedure is done for other reasons. Sometimes, when they reach a very large size, they may present as palpable abdominal masses or with events of abdominal pain. A small percentage of these tumours can be hormonally active and secrete catecholamines, vasoactive intestinal polypeptides or androgenic hormones. This fact explains that some patients with ganglioneuromas could have diarrhoea, virilisation and hypertension [2].
CT and MRI are the most used imaging procedures to identify and diagnose retroperitoneal ganglioneuromas. On non-contrast CT, they usually appear as oval or lobulated, well-circumscribed, homogeneous, hypo-dense masses. They normally surround major blood vessels, narrowing them only slightly or not at all. They may have punctate and discrete calcifications in 20-30% of cases, rather than amorphous and coarse as in neuroblastoma [3]. In the cases where there is a high amount of mixoid stroma, these tumours present a higher enhancement rate of intravenous contrast on delayed phases [4].
With MRI, on T1-weighted images, ganglioneuromas use to have a homogeneous low signal and their intensity signal on T2-weighted images depends on the proportion of myxoid stroma to cellular components and collagen fibres they have, being more hyper-intense when the tumour has a high amount of myxoid [5].
Differential Diagnosis List
Retro-peritoneal ganglioneuroma
Pheocromocytoma
Neuroblastoma
Neurofibroma
Retroperitoneal sarcoma
Final Diagnosis
Retro-peritoneal ganglioneuroma
