Understanding Mediastinal Findings After Breast Cancer Treatment: Should You Get a PET Scan?

Question
I had Stage1 IDC in 2005. SNB done and nodes were clean. I underwent chemo and radiation (lumpectomy)  I am not on any follow-up med such as Tomoxifen.  I am ER/PR+ Her2-.  My recent CT scan showed a 7-8mm soft tissue density seen along the anterior mediastinum. The anterior sternomanubrial region to be intact despite the subtle soft tissue attenuation.  Do I need to push for a PET scan on my next 6 month check?  Should I be concerned now or play the waiting game to see if the cancer has returned?  

Answer
I never understood the waiting game myself since I think the patient has a right to know as quickly as possible. So I think you should push for both a PET scan AND - if possible - a biopsy (should be possible I think with a mediasinoscopy).
Good luck! Please do keep me posted!
THANKS! Sorry I meant a mediastinoscopy.