The first step should be to attempt to locate any and all previously taken X-rays.
Based on the X-ray description, below, I would agree with the statement: “Impression:
Large calcified mass between chondral regions of righ 3rd and 4th ribs. No clear plane with sternum and pleural. differential diagnosis includes calcified chondroma, chondrosarcoma, fibrous dysplasia or calcified pleural mass. Calcification is often but not always a sign of a benign lesion.
My recommendation is, that given that the Radiologist said that “he has not seen this before”, that he/she seek a second opinion from a subspecialist, a Thoracic Radiologist. It may not be possible to make a diagnosis without a biopsy of this lesion.
Good luck
There is a typo. Supposed to be bone growth in lung