This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Radiology
Egg shell calcification seen in silicosis is due to 
Select and explain. 
A. Hilar lymphnode enlargement, B. Pleural thickening, C. Pulmonary edema, D. Dilated vessels
A: Hilar lymphnode enlargement
Answer: A: Hilar lymphnode enlargement 
Explanation: (a) Hilar lymphnode enlargement > Enlargement of the hilum is common with chronic and accelerated silicosis. In about 5-10% of cases, the nodes will calcify circumferentially, producingso-called "Eggshell" calcification.> This finding is not pathognomonic (diagnostic) of silicosis. In some cases, the pulmonary nodules may also become calcified.