Mediastinal lipoma and well-differentiated liposarcoma usually grow slowly and remain asymptomatic. When these tumors reach a huge size, which compress the adjacent structures, they will cause symptoms such as superior vena cava syndrome, Horner’s syndrome, dysphagia, dyspnea, cough, spinal nerve paralysis, tachycardia, and heart failure [
3‐
6].
There are five histological types of liposarcomas: well-differentiated, mucus, dedifferentiated, pleomorphic, and round cell. Well-differentiated liposarcoma is the most common type of liposarcoma, which can be further classified into three types: lipoma-like, sclerosis, and inflammatory [
7]. Sometimes it is difficult to differentiate lipoma and lipoma-like well-differentiated liposarcoma, especially when the tumor is giant in size. On CT scan, both of these two tumors have homogeneous fat attenuation of approximately -100HU [
1], while the fibrous septa of well-differentiated liposarcoma may be thicker, more irregular, or more nodular than lipoma [
8]. MRI is more helpful to determine the soft tissue involvement, which has an 83% accuracy rate on diagnosing well-circumscribed liposarcomas [
9]. Molecular pathological examination of the MDM2, CDK4 and p16 gene in tumors provides the diagnostic gold standard in distinguishing well-differentiated liposarcoma from lipoma [
10]. MDM2 can inhibit the transcriptional activity of p53, which inhibits the tumor suppressor function of p53. CDK4 can promote the progression of cell cycle from G1 phase to synthesis phase, which accelerates cell proliferation. p16 can decelerate the cell cycle progression from G1 phase to synthesis phase, which acts as a tumor suppressor. Using the combination of MDM2, CDK4 and p16 is helpful in distinguishing well-differentiated liposarcoma from lipoma, and it had been suggested that the use of fluorescence in situ hybridization (FISH) to access MDM2 gene amplification is more sensitive and specific than immunohistochemistry in distinguishing well-differentiated liposarcoma from lipoma [
10].
Neither lipoma nor liposarcoma is sensitive to chemotherapy or radiotherapy, and complete surgical resection is the first-line treatment choice [
5]. When the tumor is enormous and solid, it is inadequate to use the thoracoscopic approach since complete tumor resection maybe difficult using this approach. Thus, extensive thoracotomy or standard median sternotomy is needed for this situation to provide a better exposure. In some cases when a large tumor compressing the heart, extracorporeal circulation can be used to ensure the safety and reliability [
4].
In this case, the essential of the operation was to expose the tumor clearly and to resect it completely. In order to achieve those purposes, we chose extensive thoracotomy through the 3th intercostal instead of thoracoscopic approach to provide a better exposure and to ensure the safety of the surgery. The technical key point of excising such a huge mass is to find the pedicle of the tumor in the first place, and then isolate the tumor along the pedicle.