Undiff. Pleomorphic Sarcoma : Differential Diagnosis

Comments:
Differential Diagnosis of Undifferentiated Pleomorphic Sarcoma (UPS):

Dedifferentiated Liposarcoma: The vast majority of tumors in the retroperitoneum that look like UPS are in fact dedifferentiated liposarcomas. Usually, foci of well-differentiated liposarcoma are present. There is evidence of MDM2 and/or CDK4 amplification by immunohistochemistry and/or molecular tecchniques.

Case History: This image is from a retroperitoneal tumor removed from an elderly patient who presented with vague abdominal discomfort and weight loss. An abdominal and pelvic CT showed a large retroperitoneal mass compressing the large bowel. Gross examination of the resected specimen showed a 20 cm, well-circumscribed, tan, lobulated mass with foci of hemorrhage and necrosis. MDM2 amplification was confirmed by molecular techniques, supporting the diagnosis of dedifferentiated liposarcoma.