Question about "abnormal soft tissue fullness".?

I had a chest x-ray due to coughing. My physician reviewed the x-ray and determined it was bronchitis and then prescribed medication. Now two days later I get a call from my physicians office and they stated they found an "abnormal soft tissue fullness" on the x-ray and they are scheduling me for a CT scan of my chest this week. Does anyone know what possible diagnoses it could be? Should I be worried? Thank you.....