Other tumors, including lung cancer, pulmonary sarcoma, and mesothelioma, can present as large masses occupying most of the hemithorax, although these are usually accompanied by local or systemic features of malignancy such as pain, weight loss, anorexia, or paraneoplastic phenomena. Other radiologic features usually accompany malignant large-volume thoracic tumors, including significant adenopathy or a moderate-to-large pleural effusion, neither of which were seen in our patient. Benign and malignant solitary fibrous tumors of the pleura can also be very large at the time of presentation. Unlike the CT scan appearances of our patient in Figure 2, these rare tumors usually have an acute angle with the associated pleural surface from which they arise, demonstrate contrast enhancement because of considerable vascularity, and only rarely have calcified foci.10 The presence of radiographic calcification in chondroid hamartomas is related to the size of the tumor, and is observed in 75% of those that enlarge to ≥5 cm in diameter.10,12 The CT scan of our patient showed a well-circumscribed, smooth-edged (although very large), non–contrast-enhancing tumor featuring hypodense areas consistent with fat, and also areas of calcification associated with cartilage and bone formation, although difficulty remained in positively identifying the relationship between the mass and the pleural surface. In this situation, a combination of the clinical context and the radiologic findings made chondroid hamartoma the most likely diagnosis. When uncertainty remains about the origin of large thoracic masses, MRI can be helpful in differentiating intraparenchymal from pleural tumors. The rapidly declining cardiovascular status in the patient described precluded this type of potentially diagnostic imaging prior to definitive surgical intervention.