Dedifferentiated liposarcoma of retroperitoneum with extensive osteosarcomatous component

Dedifferentiated liposarcoma (DDLS) is a rare subtype of liposarcoma composed of 2 components: a well-differentiated liposarcoma (WDLS) and a nonlipogenic sarcoma (dedifferentiation component), represented in >90% of cases by a high grade undifferentiated pleomorphic sarcoma, in the form of both small microscopic foci and/or grossly recognizable nodular masses. The paper reports a rare case of a retroperitoneal DDLS, in which approximately half of a tumor mass is composed of a high-grade osteosarcoma. A 68-year-old Caucasian woman affected by abdominal discomfort. Clinical examination showed a large, hard and fixed abdominal mass. Computed tomography scan revealed a huge retroperitoneal mass composed of 2 distinct components: the upper part showed a hypodense tissue, while the lower part showed a higher density and coarse calcifications. Patient underwent to a challenging surgical resection of the mass that, at histological examination, resulted to be a DDLS, in which a WDLS coexisted with an osteosarcoma. Presurgical diagnosis of DDLS is difficult due to the great morphologic variability of the dedifferentiated component, ranging from low to high-grade nonlipogenic sarcoma. The present case contributes to widen the morphological spectrum of DDLS, emphasizing the possibility that a retroperitoneal mass with a dual tissue component, one of which containing extensive areas with coarse calcifications, is highly suspected to be a DDLS with an osteosarcomatous component. This pre-operative finding should alert the surgeon because it has a significant impact on prognosis, increasing the risk of local recurrence and of death by disease in a few months after diagnosis.