What does haziness is seen in left retrocardiac area mean? thanks

Interpretation xray: This retrocardiac area haziness sounds like a description on chest radiograph report. On the anterior posterior projection an indestinct density is seen behind the heart border in the left lower lobe, which could represent volume loss or atelectasis, pneumonitis, tumor etc. The relevance of this finding depends on clinical symptoms such as cough, fever, wheezing, etc.