Upper Extremity Dedifferentiated Liposarcoma With an Osseus Component: An Uncommon Pathology.

Liposarcomas are the most common soft tissue sarcoma primarily originating in deep soft tissues and the retroperitoneum. Sarcoma classification includes atypical lipomatous tumor/well-differentiated liposarcoma (WDL) and dedifferentiated liposarcoma (DDL), myxoid liposarcoma, and pleomorphic liposarcoma. DDL is most prevalent in the retroperitoneum and often has two distinct components, a well-differentiated lipomatous component and a dedifferentiated nonlipomatous component that could be morphologically similar to malignant fibrous histiocytoma (MFH) or fibrosarcoma. DDLs can undergo heterologous differentiation into multiple cancer types including rhabdomyosarcoma, chondrosarcoma, melanoma, and leiomyosarcoma. Rarely, DDLs can undergo metaplastic bone formation. We report a peculiar case of a DDL with an osseous component.