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Findings:The chest radiograph shows a huge mass involving the upper two thirds of the right hemithorax. Its border with the adjacent lung is sharp, and it causes anterior deviation of the trachea on the lateral film. There is a marked thoracic scoliosis associated with this mass, but no gross bony invasion or significant neural foraminal widening. Of note, a chest radiograph three years previously showed this mass to be essentially stable.
Chest CT confirms a large posterior/middle mediastinal mass with invasion of the subcarinal space. There is peripheral calcification in the mass. There is the suggestion of more central low attenuation areas within the mass.
Diagnosis: Ganglioneuroma.
Discussion: This case illustrates many of the classic features of a posterior mediastinal mass. Its sharp interface with the lung, the associated spinal changes and the anterior tracheal deviation all point to a mediastinal origin. The stable appearance over three years further narrows the differential. In the setting of scoliosis, the possibility of neurofibromatosis should be considered. The most common lesion in the posterior mediastinum in patients with neurofibromatosis is a lateral meningocoele, though in this patient the large size of the mass also raises the question of a neurofibroma. Masses that attain this size have an increased risk for malignant degeneration into neurofibrosarcoma, and should be considered in the setting of increased pain, bony destruction or sudden increase in size.
Slow growing masses in the posterior mediastinum in adults often represent tumors of the peripheral nerves or sympathetic or parasympathetic chain, namely paragangliomas or ganglioneuromas.
Ganglioneuromas are a common cause of a posterior mediastinal mass in a young adult. They usually present in the second or third decade, and are seen equally in males and females. Histologically, they demonstrate mature ganglion cells. They are frequently calcified, as seen in this patient, a feature which can help differentiate them from neurofibromas and schwannomas.
References:
1. Naidich DP, Zerhouni EA, Siegelman SS. Computed Tomography and Magnetic
Resonance of the Thorax. New York. Raven Press 1991.
2. Kumar AJ, Kuhajda FP, et al. CT of Extracranial Nerve Sheath Tumors.
JCAT 1983;7:857-865
3. Kawashima A, et al. CT of Posterior mediastinal Masses. Radiographics. 11:1045-1067, 1991.
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