British Journal of Radiology (2007) 80, e238-e240
© 2007 British Institute of Radiology
doi: 10.1259/bjr/97270791
Posterior mediastinal dumbbell ganglioneuroma with fatty replacement
S-M Ko, MD
1
D-Y Keum, MD
2 and
Y-N Kang, MD
3
Departments of 1 Radiology, 2 Thoracic Surgery and 3 Pathology, Dongsan Medical Center, Keimyung University College of Medicine, Daegu, Republic of Korea
Correspondence: SungMin Ko, Department of Radiology, Dongsan Medical Center, Keimyung University College of Medicine, 194 Dongsan-dong, Jung-gu, Daegu 700-712, Republic of Korea. E-mail: ksm9723{at}yahoo.co.kr
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Abstract
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We report a case of a posterior mediastinal dumbbell ganglioneuroma with fatty replacement on CT and MRI. Most dumbbell tumours are neurogenic in origin. Fatty replacement of non-lipomatous malignancies is rare. This report suggests that a ganglioneuroma with fatty replacement should be added to the differential diagnosis of fat-containing posterior mediastinal tumours.
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Introduction
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Ganglioneuromas typically occur in adolescents and young adults and represent the most common tumour arising in the posterior mediastinum in these age groups. These tumours may be diagnosed incidentally during imaging studies performed for other reasons [1, 2]. Fatty replacement in cases of ganglioneuroma is very rare and, radiographically, only one case has been reported in the literature [3]. Herein, we report a case of a posterior mediastinal dumbbell ganglioneuroma with fatty replacement in a middle-aged woman.
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Case report
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A 53-year-old woman presented with a chest radiograph abnormality. She had no neurological symptoms or signs. The initial chest radiograph taken 3 years previously showed a large right upper posterior mediastinal mass with no obvious destruction of the adjacent vertebral bodies or posterior ribs (Figure 1
). At that time the patient refused a core needle biopsy of the mass. She did not return to our hospital for the follow-up study until March 2005. There was no significant change in size and shape of the mass on chest radiography during the 3 year interval. Unenhanced chest CT showed a right paraspinal mass measuring approximately 9.0 x 4.5 x 10.0 cm that was well circumscribed and which contained mixed attenuation including fat and soft tissue elements. The tumour extended into the spinal canal through the enlarged right intervertebral foramen of T3–4 (Figure 2a). Contrast-enhanced CT revealed that the tumour crossed into the left posterior mediastinum and abutted on the descending thoracic aorta. The soft tissue component enhanced minimally (Figure 2b). Contrast-enhanced MR imaging of the thorax was performed to evaluate spinal cord compression. T1 weighted axial images showed that the mass had a mixed signal intensity with the same morphology as seen on thoracic CT (Figure 3a). T2 weighted axial images demonstrated that the mass encased the descending thoracic aorta without compression (Figure 3b). On axial contrast-enhanced T1 weighted images with fat saturation, the signal intensity of the areas of fat was reduced but the nodular and stranding soft tissue components were enhanced (Figure 3c).
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Figure 1. Chest radiograph obtained 3 years previously showing a large mass in the right side of the posterior mediastinum with no rib destruction(arrow).
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Figure 2. (a) Unenhanced CT scan obtained above the aortic arch shows the right paraspinal tumour composed of both fat and soft tissue attenuation. The mass has some stranding and nodular soft tissue density (arrow) within the fatty area. Note the growth into the neural foramen (arrowhead). (b) Contrast-enhanced CT scan obtained at the level of the carina shows the mass abutting on the descending thoracic aorta (arrow). The soft tissue component shows minimal enhancement.
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Figure 3. (a) The T1 weighted axial image shows that the mass has not only the low signal intensity of nodular and stranding soft tissue components but also the high signal intensity of the fatty areas. The dumbbell tumour enlarges the right intervertebral foramen of T3–4 and displaces the thecal sac to the left without compression of the spinal cord. (b) On the T2 weighted axial image, the mass extends through the pre-vertebral space to the left posterior mediastinum and encases the descending thoracic aorta without compression. (c) The axial contrast-enhanced T1 weighted image with fat saturation demonstrates that the signal intensity of the fatty areas is reduced but that the nodular and stranding soft tissue components are enhanced.
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The patient underwent surgery to remove the dumbbell tumour for prevention of spinal cord compression. The mass was removed using a right posterolateral thoracotomy incision. The tumour was tightly attached to the vertebral column and connected to the epidural mass through the T3–4 enlarged intervertebral foramen. Most of the epidural mass was removed; however, part of the mass tightly attached to the spinal cord was not removed completely. Microscopic examination of the surgical specimen (Figure 4) showed a large amount of adipose tissue surrounding the dense stromal elements composed of relatively mature ganglion cells, Schwann cells and nerve fibres. As a result, the pathological diagnosis of ganglioneuroma with fatty replacement was made.
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Figure 4. Microscopic findings of the specimen demonstrate an interlacing pattern of adipose tissue and fibrocellular tissue composed of relatively mature ganglion cells, Schwann cells and nerve fibres(inset).
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Discussion
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To our knowledge, radiographically, ganglioneuroma with fatty replacement has been described only once previously [3]. In our case the patient was a 53-year-old woman and the fat-containing mass was located in the right posterior mediastinum with extension into the spinal canal and the opposite posterior mediastinum. Fatty replacement of non-lipomatous malignancies is rare. Pathologically, a fat component is seen commonly in schwannoma but rarely in ganglioneuroma [4, 5]. Because ganglioneuromas represent the most common posterior mediastinal tumours in young patients, it is possible that this 53-year-old patient's tumour arose years earlier and subsequently experienced spontaneous degeneration with fatty replacement as described in the previous report [3].
Ganglioneuromas are well-encapsulated benign tumours that arise most commonly from the sympathetic ganglia in the posterior mediastinum. These tumours may grow through the adjacent intervertebral foramen and extend into the spinal canal with a "dumbbell" or "hourglass" configuration. Patients are usually asymptomatic despite the large tumour size. These tumours may be diagnosed incidentally during imaging studies performed for other reasons. On a chest radiograph they are seen as sharply marginated, oblong masses with a broad base along the anterolateral aspect of the spine with little mass effect relative to the size of the tumour. They may show low attenuation on unenhanced CT and little or moderate enhancement on contrast-enhanced CT. MRI usually shows a homogeneous, intermediate-signal intensity on all sequences, occasionally with a "whorled" appearance caused by curvilinear or nodular bands of low intensity on both T1 and T2 weighted images [1, 2].
The differential diagnosis of fat-containing posterior mediastinal masses includes lipoma, liposarcoma, angiolipoma, mediastinal lipomatosis, teratoma and neurogenic tumour with fatty replacement. Mediastinal liposarcomas are rare in adults older than 40 years but, when they occur, these tumours are usually located in the posterior mediastinum. On CT and MRI, liposarcomas show a unique mixture of fat interspersed with irregular strands or masses of soft tissue and poor definition of adjacent mediastinal structures with infiltration or invasion [6–8]. Posterior mediastinal angiolipomas are extremely rare, benign, fat-containing tumours and occur mainly in young adults. These tumours may have a dumbbell shape and show an inhomogeneous enhancement pattern according to the ratio of adipose to vascular tissue [9, 10]. A mature teratoma in a posterior mediastinal location would be very unusual in a patient of this age [11, 12]. Our initial working diagnosis of the tumour in this case was therefore a liposarcoma despite its growth into a single neural foramen. We favoured a well-differentiated liposarcoma over a poorly differentiated liposarcoma because there had been no change in the appearance of the tumour on chest radiography during the 3 year interval despite its nodular and stranding soft tissue components on CT and MRI. Given the size, extensive nature and fat component of the mass, a neurogenic tumour seemed unlikely, even though most dumbbell tumours are neurogenic in origin [13]. A ganglioneuroma was also not considered because of the age of our patient.
In conclusion, we report a case of a posterior mediastinal dumbbell ganglioneuroma with fatty replacement extending into the spinal canal and the opposite posterior mediastinum on CT and MRI. Ganglioneuroma with fatty replacement should be added to the differential diagnosis of fat-containing posterior mediastinal tumours.
Received for publication July 16, 2006.
Revision received October 23, 2006.
Accepted for publication November 6, 2006.
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References
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Abstract
Introduction
