[Dedifferentiated liposarcoma of extremities: a clinicopathologic analysis].

Objective: To study the clinicopathologic features of dedifferentiated liposarcoma of extremities. Methods: Nine cases of dedifferentiated liposarcoma of extremities diagnosed at Beijing Jishuitan Hospital from 2009 to 2017 were selected. The histological features of cases of dedifferentiated liposarcoma of extremities were evaluated by HE and immunohistochemistry, together with the clinical and radiological features. Flourescence in situ hybridization(FISH) was used to detect MDM2 amplification. Results: They were located in the thigh (6 cases), calf (2 cases) and buttock (1 case). There were six females and three males. Patients' age ranged from 61 to 79 years (mean 68 years). Histologically, there were two components, well-differentiated liposarcoma and dedifferentiated sarcoma with or without transitional lesions between them. The histology of dedifferentiated liposarcoma included undifferentiated sarcoma and fibrosarcoma. Heterologous elements such as bone and cartilage were present in two cases. Immunohistochemical study showed the tumor cells expressed vimentin, CDK4 and p16. MDM2 were positive in 6 cases (6/9) and p53 was positive in one case(1/9). CKpan was positive in the epithelioid differentiation area. S-100 protein was positive in the well-differentiated liposarcoma component. FISH showed the amplification of MDM2(6/9). Conclusions: Dedifferentiated liposarcoma of extremities is very rare. The diagnosis should be combined with the histological characteristics and immunohistochemical results and differentiated from the other tumors and tumor-like lesions.