Liposarcoma–a mesenchymal malignant tumor that contains lipoblasts–is the most common soft tissue sarcoma and accounts for 20% of all mesenchymal tumors . The tumor occurs most frequently in the limbs and retroperitoneum and rarely originates in the heart . Peak incidence is between 40 and 60 years old, and there is a slight male predominance . Liposarcoma of the heart is an extremely rare sarcoma, with less than 35 cases reported in the literature according to literature . To our best knowledge, this is the first reported case of simultaneous atypical lipoma in the right atrium and pericardium.
Liposarcomas can be divided into four subtypes: Well-differentiated liposarcoma (or atypical lipoma), myxoid/round cell liposarcoma, pleomorphic liposarcoma, and dedifferentiated liposarcoma. Atypical lipoma was the most common subtype (50%), which had been observed in the atrium and the pericardium. The tumor usually grows slowly, insidious and remain asymptomatic until reach a giant size. Atypical lipomas can be asymptomatic or symptomatic depending on their size and location within the heart. They can invade adjacent organs, so they are more likely to be symptomatic than benign lipomas. Atypical lipomas have a mild biological behavior and do not generally metastasis, but there is a possibility of focal recurrence.
Although pathological diagnosis serves as a gold standard of diagnosis of atypical lipoma, echocardiography is still essential. Echocardiography is an ideal and important diagnostic modality since it can provide information of the tumor on the size, location, boundary, modality, amount blood flow and so on. Although echocardiography offers a simple and non-invasive approach, it cannot conclusively differentiate between atypical lipomas and other primary tumors of the heart. Computed tomography or magnetic resonance imaging may be of additional value.
There are several diseases should be differentiated from atrial atypical lipomas, namely myxoma, thrombus, benign lipoma. Atrial myxoma is the most frequent primary cardiac tumor in adults. It usually arises in the area of the fossa ovalis, grows on pedicles, has the manner of soft and polyps. The tumor may move towards the ventricle during diastole. Atrial thrombus is usually associated with a history of atrial fibrillation or rheumatic heart disease, and ventricular thrombosis usually occurs on the basis of abnormal wall motion. The base of the thrombus is wide and can have activity. As time progresses, the echo of the thrombus can gradually change. The size of the thrombus may change after anticoagulant therapy. Cardiac benign lipomas can originate either from the subendocardium (50%), subpericardium (25%), or myocardium (25%) and maybe located more frequently in the left ventricle or right atrium . Cardiac benign lipomas are most often detected incidentally and do not have specific ultrasound findings. The lipoma demonstrated typical loss of signal on fat suppressed magnetic resonance imaging sequence techniques.
Pericardial atypical lipomas may confuse with malignant mesothelioma, pericardial cyst, hemangiomas. The ultrasound manifestations of malignant mesothelioma usually include pericardial effusion, pericardial thickening, pericardial cavity mass. Pericardial cysts are usually congenial lesion or acquired . Echocardiography showed an isolated, unilocular, smooth-walled cystic mass adjacent to the heart. There was no communicating tract between mass and heart cavity, and no blood flow signal within the mass. Cardiac hemangiomas are extremely rare and account for approximately 2% of all primary resected cardiac tumors. They can locate in atrium、ventricle、pericardium and endocardium . Echocardiography usually presents as a hyperechoic mass with a well-defined boundary, and myocardial contrast echocardiography can demonstrate the vascularity of the mass.
In conclusion, we report a very rare case of a huge atypical lipomas located on the pericardium and right atrium. These tumors were easily detected by echocardiography and final diagnosed after surgical resection and pathological examination. He is under follow-up for the possibility of recurrence.