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Case of the Month



Dedifferentiated liposarcoma

This case is from a 28 year old female who presents with a large 22 cm retroperitoneal mass. The differential diagnosis included: dedifferentiated liposarcoma, GIST tumor, and synovial sarcoma. Molecular studies showed a positive MDM2 and negative DOG1, CD34, CD117, cytokeratin, and desmin supported the diagnosis of dedifferentiated liposarcoma and not GIST tumor or synovial sarcoma.

Liposarcoma is the most common malignant tumor in the retroperitoneal soft tissue, and this tumor is classified according to the amount of lipid inside the cells, the mucoid lipid and the degree of cell differentiation. This tumor is classified into the well differentiated, myxoid, round cell, pleomorphic and dedifferentiated types, and the pleomorphic type is known to be the most common type. The dedifferentiated liposarcoma refers to a condition in which well and poorly differentiated liposarcoma and non-lipomatous sarcoma coexist in one tumor. This type has a vague prognosis compared to other types of sarcoma, and making the histological diagnosis can be difficult.

Dedifferentiated liposarcoma commonly develops in the retroperitoneum, limbs, testis and spermatic cord.

The microscopic images show a spindle cell neoplasm with 3-4 mitoses per 10 high power fields. No necrosis and no evidence of well differentiated liposarcoma.