Surgical Pathology Criteria

Dedifferentiated Liposarcoma

Differential Diagnosis

Pleomorphic Liposarcoma Dedifferentiated Liposarcoma
Cellular pleomorphic sarcoma throughout Atypical lipomatous areas present
MDM2 and CDK4 negative MDM2 95% and CDK4 92%
Classically, pleomorphic liposarcoma was not permitted as the dedifferentiated component, but it appears that it rarely occurs in this guise, associated with atypical lipomatous tumor and expressing MDM2 (see Boland 2010).

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

Dedifferentiated Liposarcoma GIST (spindled, cytologically malignant)
Frequently markedly pleomorphic Pleomorphism infrequent, even in malignant lesions
CD117, DOG1 negative CD117, DOG1 85-95%
CD34 may be positive in both

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