Pleural mouse

Case contributed by Yi Tong


Shortness of breath, HIV+

Patient Data

Age: 55 years
Gender: Male

There is a rounded 16mm structure with central coarse calcifications in the dependent portion of the right hemithorax, located within the pleural space. Compared to a CT from 8 years prior, this structure has shifted in position (mobile) and demonstrates progression of central calcifications. There are unrelated bilateral pleural effusions and a right lower lobe airspace consolidation. 

CT Chest from 8 years prior


A CT Chest from 8 years prior demonstrates a lesion of similar size and containing central calcifications, in a different location (paravertebral, abutting the posterior pleura). 

Case Discussion

Pleural mouse (also known as pleural fibrin body or thoracolithiasis) refers to a calcified or non-calcified loose body in the pleural space. They can be single or multiple, and a pathognomonic feature is their mobile nature. Although the exact etiology is not known, they are theorized to represent sequelae of prior pleural effusion/hemothorax or necrosis of mediastinal/pericardial fat.  They are rarely symptomatic, and most often detected incidentally. 

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