PMC3955859_01
PA CXR showing a right sided round soft tissue mass lesion probably in the right posterior mediastinum
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A PA chest X-ray showed a right sided large spherical shadow with clear-cut margins probably in the posterior mediastinum (Figure 1). 
Axial CT scan at the level of the carina shows a lobulated enhancing soft tissue lesion in the right posterior mediastinum
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The mass was located in the position of the azygos vein (Figure 2). 
MRI of the thoracic region showing signal void tubular structure in the right paravertebral space
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MRI study (Figure 3). Magnetic resonance angiography (MRA) showed an enhancing saccular right paravertebral vascular lesion draining to the azygos vein through a wide neck in the thoracic region.
Contrast enhanced MRA study of the thoracic aorta demonstrating a saccular enhancing vascular lesion with a wide neck connecting to the azygos vein on the right side
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With regards to the abovementioned findings, the impression was aneurysmal dilatation of the azygos vein (Figure 4). 
CT angiography after 3 months. No growth or thrombosis was detected.
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In CT angiography after 3 months, no growth or thrombosis was detected (Figure 5).