Almost all primary retroperitoneal liposarcomas can be classified as well-/dedifferentiated liposarcoma. Rarely, however, primary retroperitoneal liposarcoma is classified as myxoid/round cell liposarcoma, based on the presence of myxoid areas and vascular crow’s feet pattern, which has resulted in a debate on the classification of liposarcoma in the retroperitoneum.
Genetically, myxoid/round cell liposarcoma and well-/dedifferentiated liposarcoma are different diseases.
Myxoid/round cell liposarcoma is characterized by a translocation causing FUS-CHOP or EWSR1-CHOP fusion, whereas well-/dedifferentiated liposarcoma is characterized by an amplification of the 12q13-15 region, including MDM2 and CDK4 genes.
As myxoid/round cell liposarcoma is highly radio- and chemosensitive, differentiation between subtypes is important to optimize treatment. We studied whether primary retroperitoneal liposarcomas diagnosed as myxoid/round cell liposarcoma represent molecularly true myxoid/round cell liposarcoma or are histopathological mimics and represent well-/dedifferentiated liposarcoma.
References
de Vreeze RS, de Jong D, Tielen IH, Ruijter HJ, Nederlof PM, Haas RL, van Coevorden F. Primary retroperitoneal myxoid/round cell liposarcoma is a nonexisting disease: an immunohistochemical and molecular biological analysis. Mod Pathol. 2008 Sep 26. PMID: 18820664
Hisaoka M, Morimitsu Y, Hashimoto H, Ishida T, Mukai H, Satoh H, Motoi T, Machinami R. Retroperitoneal liposarcoma with combined well-differentiated and myxoid malignant fibrous histiocytoma-like myxoid areas. Am J Surg Pathol. 1999 Dec;23(12):1480-92. PMID: 10584701