CARTILAGINOUS DISORDERS OF THE CHEST

Cartilaginous disorders of the thorax can arise in the parenchyma, air ways, chest wall, and axial skeleton. At radiography, pulmonary hamart oma is characterized by ''popcorn'' calcification or fat density, eith er of which is diagnostic. Bronchiectasis is best demonstrated at high -resolution computed tomography (CT) and has a ''tramline'' or ''signe t ring'' appearance, Tracheopathia osteochondroplastica appears at CT as multiple sessile submucosal nodules with or without calcification a long the cartilaginous portion of the trachea. In relapsing polychondr itis, the trachea and mainstem bronchi have diffuse or focal thickenin g with luminal narrowing at radiography, Costochondritis of the chest wall has become more prevalent with increased intravenous drug abuse a nd may be demonstrated at CT as soft-tissue swelling along with underl ying cartilaginous fragmentation and bone destruction. Enchondromas ar e expansile and may display a calcified cartilaginous matrix at radiog raphy, In osteochondroma, the thickness of the cartilaginous cap deter mines the likelihood of malignant degeneration. At radiography, chondr oblastomas have a. round contour, sharp margins, and cortical scallopi ng, whereas chondrosarcomas are large masses with indistinct margins, cortical breakthrough, and soft-tissue extension. By identifying eithe r a process affecting a cartilage-containing structure or a cartilagin ous matrix within a lesion, the chest radiologist may be able to narro w the list of differential diagnostic possibilities substantially.