Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral chest radiographs . Left retrocardiac opacity continues to improve , but has not resolved . Nodular density overlying the anterior right 2nd rib is not seen on priors . Tracheomegaly is again noted . There is no pleural effusion or pneumothorax . The cardiomediastinal silhouette is normal .
    OUTPUT:
    
Persistent retrocardiac opacity slowly improving over the course of three months may represent scarring . Also , questionable nodular density in the right upper lobe may artifactual considering it appeared over the course of 4 weeks . Further charachterization of these findings with CT is reasonable . Findings were submitted to the radiology communications dashboard .