Your son could have both Sjogren’s syndrome and sarcoidosis. Sjogren’s Syndrome is a chronic inflammatory condition that causes dryness of the mucous membranes like the eyes and mouth. Sarcoidosis is a disease that causes small clusters of inflammation, called granulomas. The granulomas can occur in any area of the body, but are most common in the lungs, lymph nodes, eyes, and skin.
There is no easy way to rule out lymphoma as a cause of the hilar lymph node enlargement. If this is sarcoidosis, it is unlikely that there will be further enlargement of the nodes. If this is lymphoma, there probably will be further enlargement of the nodes. You must discuss your question of a safe period of watchful waiting with your son’s doctors.
If a biopsy is to be done, he should have a CT scan done to see if there is any mediastinal lymph node enlargement. He could then have mediastinascopy with biopsy. This is a relatively easy and safe procedure.