Presentation
Known case of Hodgkin lymphoma.
Patient Data
There is a soft tissue mass which we can visualize pulmonary vessels through it. So, the mass is probably located either anterior or posterior to the hilum, but not at the hilum. This is known as the hilum overlay sign.
There is a soft tissue mass which we can visualize pulmonary vessels (red line) through it. So, the mass is probably located either anterior or posterior to the hilum, but not at the hilum. This is known as the hilum overlay sign.
Case Discussion
Pulmonary vessels and their silhouette will be obliterated if the mass arises from the hilum. On the other hand, if the edges of the vessels are appreciated, it can be concluded that the mass is not in contact with the hilum and is either anterior or posterior to it.