Case Report: Giant myxosarcoma involving both atria

Background Primary cardiac tumors are uncommon, with an incidence rate ranging from 0.001‰ to 0.3‰. Among cardiac tumors, 75% are benign and 25% are malignant. Approximately 50% of benign cardiac tumors are myxomas, while 75% of malignant cardiac tumors are sarcomas. Compared with myxomas, malignant cardiac tumors have a poorer prognosis. Cardiac myxosarcomas often have an insidious onset in young and middle-aged patients, with an overall survival period of 6 to 12 months. Similar to soft tissue tumors, cardiac sarcomas also consist of a range of histological subtypes. Among these, cardiac myxosarcomas are extremely rare, with only a few case reports documented in domestic and international literature to date. Due to similarities in imaging findings, they are often diagnosed as myxomas preoperatively, which may lead to insufficient resection during surgery. Owing to similarities in gross and histological features, coupled with the rarity of such cases, a small number of cases are misdiagnosed as myxomas in postoperative pathological examinations, and a definitive diagnosis is only made upon recurrence. This paper reports a case of a 23-year-old male patient with congenital heart disease and atrial septal defect, who had a history of interventional occlusion for atrial septal defect 12 years ago. The patient was admitted to the hospital for a rare giant myxosarcoma involving both atria, manifesting as rapidly progressive hemodynamic compromise. He underwent surgical resection of the cardiac tumor, and the pathological diagnosis was cardiac myxosarcoma. The tumor demonstrated highly malignant biological behavior. Rapid postoperative recurrence occurred, resulting in a short survival period. The patient eventually died of vena cava obstruction, heart failure and multiple organ failure secondary to tumor recurrence.