Relapse of a cardiac tumor from myxoma to low-grade malignant myofibroblastic sarcoma: malignant transformation or metachronous lesion?

A 47-year-old woman, who had undergone cardiac myxoma removal surgery six years ago, was readmitted due to a 2-week history of chest distress, and dyspnea with the change of body position. Both the examinations and the surgery confirmed a cardiac tumor relapse. Histology demonstrated that the mass resected in surgery had a pathologic change from myxoma to a low-grade malignant myofibroblastic sarcoma. The patient received heart transplantation 2 years later due to tumor recurrence, and finally died of cerebral hemorrhage.