Dedifferentiated Liposarcoma

Differential Diagnosis

Pleomorphic Liposarcoma	Dedifferentiated Liposarcoma
Pleomorphic sarcoma exhibits fatty differentiation	Contains non-lipogenic sarcoma
Cellular pleomorphic sarcoma throughout	Atypical lipomatous areas present
MDM2 and CDK4 negative	MDM2 95% and CDK4 92%

Rare tumors containing both pleomorphic liposarcoma and atypical lipomatous tumor should be designiated as a mixture of the two processes

Lipomatous Hemangiopericytoma	Dedifferentiated Liposarcoma
Cytologically bland	High grade dedifferentiated areas
No areas of atypical lipomatous tumor	Areas or history of atypical lipomatous tumor
Circumscribed	Usually non-circumscribed

Independently Arising Nono-lipogenic Sarcoma vs Atypical Lipomatous Tumor

Must be ruled out by adequate pathologic and surgical sampling
There should be a high level of suspicion for tumors arising in the retroperitoneum
Prior specimens should be examined

Radiographic evidence should be sought of a non-sampled fatty component

	MDM2	CDK4
Dedifferentiated Liposarcoma	95%	92%
MFH	11	3
Myxofibrosarcoma	42	17
Leiomyosarcoma	6	1
Maligant peripheral nerve sheath tumor	64	12