Liposarcoma Preoperatively Diagnosed as Lipoma: 10-Year Experience at a Single Institution

BACKGROUND On rare occasions, a lesion preoperatively diagnosed as a lipoma is ultimately diagnosed as a liposarcoma. It is important to differentiate liposarcomas from lipomas preoperatively. OBJECTIVE To examine characteristic features of liposarcomas preoperatively diagnosed as lipomas. METHODS Patients (n = 637) who underwent resection of tumors preoperatively diagnosed as lipomas from January 2006 to October 2016 were retrospectively reviewed. RESULTS Based on pathological examination, 8 of 637 lesions were diagnosed as liposarcomas postoperatively. All the liposarcomas were well-differentiated liposarcomas. The rate of male patients was higher (87.5% vs 38.9%) and the size of tumors was larger (8.75 vs 4.64 cm) in these cases than in accurately diagnosed lipoma cases. On imaging, nonfatty septa were more frequently observed (71.4% vs 20.0%) and were thicker (2.22 vs 1.33 mm) than in true lipoma cases. CONCLUSION If the patient with a lipomatous tumor is male and the tumor is large, we should consider the possibility of it being a liposarcoma. A thick internal septum in the image findings is a good predictor of malignancy.