Unusual location for a ganglioneuroma

A 20-year-old female presented in the Emergency Department with a five-week pelvic pain. A transvaginal ultrasound was performed which showed an isoechoic, vascularized mass measuring 5 cm located behind the rectum. Magnetic Ressonance Image (MRI) was performed later to further characterize this mass.

A pelvic MRI (Figure 1) was performed, which showed a well-bounded lesion within the presacral space, that presented avid enhancement after contrast and heterogeneous T2-hyperintensity. No fatty component was depicted. There were no signs of infiltration of adjacent organs or associated lymph node enlargement.

A Computed Tomography (CT) guided biopsy (Figure 2) was performed and the histopathologic diagnosis of ganglioneuroma was made. The mass was surgically removed and her symptoms resolved.

Ganglioneuroma is a rare and benign tumour of neural crest origin [1]. It is seen in or after the second decade of life [2] with no sex predilection[3]. They usually arise along the paravertebral sympathetic plexus. The two most common locations for a ganglioneuroma are the retroperitoneum and posterior mediastinum [3]. A presacral location of ganglioneuroma is very rare [1]. Less than twenty cases have been reported in the literature [1-3,4]. They are often asymptomatic, although nonspecific symptoms may occur due to local mass effects. Constipation, amenorrhea, neurogenic bladder, low back and leg pain have been reported in various studies as main symptoms in presacral ganglioneuromas [3].

CT and MR imaging are helpful in developing a differential diagnosis and determining the immediate local extent of the tumour.

Ganglioneuromas appear as well-circumscribed homogeneous solid masses that are hypoattenuating to muscle on CT [5]. Fine calcifications are seen in two-thirds of cases [2]. In our case, the CT didn´t show the presence of calcifications.

On MRI, they appear isointense on T1 and heterogeneous on T2-weighted images.[1] Their T2 signal intensity varies accordingly to the proportion of myxoid stroma to cellular components and on the amount of collagen fibers. Curvilinear bands of low signal intensity on T2-weighted images give the tumour a whorled appearance [5], as it is depicted on our case.

Foraminal widening is sometimes seen in these tumours. This finding may also be observed in schwannomas and neurofibromas arising in these region [1].

As far as differential diagnosis are concerned, there is a wide variety of benign and malignant presacral masses that may derive from osteochondral, neural or mesenchymal tissue.  Considering the differential diagnosis of neurogenic origin, one should keep in mind certain distinguishing features.

Neurofibromas usually have a characteristic target appearance at T2-weighted imaging which consists of a hyperintense rim of myxoid material and a central area of low signal intensity related to their fibrous core [6].

Schwannomas may remodel or erode through the sacral bone. They are heterogeneous at MR imaging, with low signal intensity on T1 and high signal intensity on T2-weighted images [6].

 Paragangliomas are highly vascular tumours and haemorrhage is common. A low-signal-intensity rim (the cap sign) may be seen. Intense contrast enhancement and flow voids are typical [6].

Chordomas are destructive lytic lesions with a large presacral soft-tissue component. They appear with high signal intensity on T2-weighted MR images and tend to show only mild contrast enhancement [6].

 Treatment of ganglioneuroma consists of surgical excision. As it is a benign tumour, no additional radiotherapy or chemotherapy is needed. Prognosis is excellent and recurrence is extremely rare [1].

Written informed patient consent for publication has been obtained.