Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is within normal limits allowing for technique . Mediastinal and hilar contours are unremarkable . There is a small triangular opacity at the medial left base , similar in location . There is no evidence for new pulmonary consolidation , pulmonary edema , pleural effusion , or pneumothorax . There are mild degenerative changes in the thoracic spine . There is advanced bilateral glenohumeral osteoarthritis , as seen previously . Left posterior rib deformities are again noted . The bones are diffusely sclerotic .
    OUTPUT:
    
Stable left triangular retrocardiac opacity .