Case Number : Case 2428- 21 October 2019 Posted By: Raul Perret

Pleomorphic Liposarcoma.

agreed Pleomorphic liposarcoma

Agree. Because the last figure appears to show a fibrous septa with atypical cells, I would like to see MDM2 to make sure that this is not a dedifferentiated liposarcoma.

Great comments. This was a case of a high grade pleomorphic liposarcoma. This is the rarest variant of liposarcoma, representing around 5% of cases. The key diagnostic features are the presence of pleomorphic cells  and lipoblasts, which may or may not be pleomorphic. Importantly, by definition lipoblasts are mono or multivacuolated cells with hyperchromatic and indented nuclei, this features MUST be present for calling a cell a lipoblast. Pleomorphic liposarcoma is mainly an HE diagnosis but MDM2 immunohistochemistry and eventually FISH should be performed in order to rule out a dedifferentiated liposarcoma with "homologous" lipoblastic dedifferentiation. This distinction is crucial as pleomorphic liposarcoma and dedifferentiated liposarcoma have very different prognosis. The former is an aggressive type of sarcoma which metastasizes in 50-60% of cases while the latter is generally a rather indolent sarcoma metastasizing 15-20% of cases.

Thanks for this great case, Raul, and especially for the helpful comments!

Agree wonderful case.