Angiosarcoma is one of the most common cardiac tumors, but early detection of this tumor is often difficult, as exemplified by our patient, a 55-year-old woman whose cardiac tumor was first detected by echocardiography. Surgical removal of the tumor was impossible due to its extensive pericardial invasion. Pathological diagnosis was not complete before autopsy because of the wide occupied necrotized area of the tumor. There is no diagnostic imaging technique available to detect such a necrotized area. An imaging technique more powerful than echocardiography and able to diagnose angiosarcoma earlier is needed.