Welcome to health care magic. 
1.The report suggest dilatation  of the thoracic 
aorta - which is pathology for your age.
2.The possibilities mentioned are as mediastinal mass or density.  
3.In this case i would recommend to get a 
CT scan with contrast if necessary for further evaluation.
4.As x-ray is only a screening tool and it will give a over view, for definitive needs further evaluation. 
5. Unfolding of aorta is seen in hypertensive patients, if you are one please control your BP.  
Good luck.
Hope i have answered your query,
any thing to ask ? do not hesitate to ask.
http://doctor.healthcaremagic.com/doctors/dr-ganesh/62888