Thanks for your question on HCM. I can understand your situation and problem. By your description I think you are having isolated mediastinal lymphnode. In old age (your age group) causes for this are 1. Benign enlargement 2. Infection 3. Calcification due to old age 4. Rarely malignancy (lymphoma) etc. So in my opinion you should not worry much. As single lymphnode is benign mostly. But better to get done repeat CT scan after 6-7 months. If lymphnode is decreasing or static than it is benign. And if increase in size than you need to consult pulmonologist and get done bronchoscopic ultrasound guided biopsy of the lymphnode.