Abstract
BACKGROUND: Angiosarcomas are soft-tissue sarcomas of endothelial cells that can arise from any site in the body. Primary mediastinal angiosarcoma is rare, with an extremely poor prognosis and currently no established treatment. Mediastinal angiosarcoma is often detected as a tumor mass in the heart, lung, aorta, or pulmonary artery. However, in cases where no tumor mass is found, a definitive diagnosis is difficult without tissue biopsy, as the condition shows various, non-specific clinical findings. CASE PRESENTATION: A 49-year-old man had an episode of syncope while walking. Cardiac catheterization and computed tomography suggested constrictive pericarditis, aortic dissection, and coronary artery disease. Scheduled total arch replacement and coronary artery bypass grafting could not be completed because intraoperative findings indicated the presence of a malignant tumor. Only pericardiectomy was performed. Hyaluronic acid concentration in the pleural fluid was high. The diagnosis of mediastinal angiosarcoma was confirmed postoperatively. CONCLUSIONS: Mediastinal angiosarcoma might mimic multiple diseases within a single case. Hyaluronic acid concentration in the pleural fluid may be a useful indicator for mediastinal angiosarcoma diagnosis.