Retroperitoneal dedifferentiated liposarcoma with osteosarcomatous components: a case report.

[dedifferentiated liposarcoma]

We report a rare case of recurrent retroperitoneal dedifferentiated liposarcoma with osteosarcomatous components . An 82 -year -old male diagnosed with recurrent retroperitoneal liposarcoma underwent a tumor resection . Histologically , osseous matrix with osteoid and mature hyaline cartilaginous tissues with high cellularity were observed in a fibrous background through most of the tumor , and scattered MDM 2 - and CDK 4 -positive atypical hyperchromatic stromal cells were detected surrounding the dedifferentiated areas . Dedifferentiation occurs in up to 10 % of well-differentiated liposarcomas , frequently resembling a malignant fibrous histiocytoma -like pleomorphic sarcoma . In contrast , divergent differentiation with osteosarcomatous components is considered to be extremely rare .