Liposarcoma round cell

Liposarcoma is easily recognized by most pathologists in its prototypical differentiated forms. Nevertheless, myxoid and round cell variants of this neoplasm often contain few if any discernible lipoblasts and may therefore be difficult to identify. 

Round cell liposarcoma is a morphologic variant of high grade MLPS that may resemble extraskeletal chondrosarcoma, cellular peripheral nerve sheath tumors, or even metastatic poorly differentiated carcinomas. S-100 protein and vimentin are seen in all these tumor types. MPNSTs that are similar microscopically to round cell liposarcoma may express CD56 or myelin basic protein, unlike adipocytic lesions. 

As mentioned earlier in this discussion, CDK4 and MDM2 immunostains can be utilized to help confirm the adipocytic nature of some problematic soft tissue tumors (namely, dedifferentiated liposarcoma). However, de Vreeze and colleagues have shown that MLPS and round-cell liposarcoma of the extremities typically lack these determinants immunohistochemically. This reflects the fact that such lesions manifest karyotypic abnormalities that are different from well-differentiated and dedifferentiated liposarcomas. ... 

The type 1 TLS/CHOP chimeric transcript is a result of the above-mentioned t(12 16) and is a very sensitive and specific molecular alteration for the myxoid/round cell liposarcoma entityOikawa and colleagues have developed a monoclonal antibody to this fusion transcript, which they claim is highly specific and sensitive with formalin-fixed paraffin-embedded tissue. However, there is no literature on its use. As a diagnostic tool, this is a good example of a genomic application of me. 

De Vreeze RS, de Jong D, Tielen IH, et al. Primary retroperitoneal myxoid/round cell liposarcoma is a nonexisting disease An immunohistochemical and molecular biological analysis. Mod Pathol. 2008 E-pub. 

Oda Y, Yamamoto H, Takahiira T, et al. Frequent alteration of pl6 (INK4a/pl4 (ARE) and p53 pathways in the round cell component of myxoid/round cell liposarcoma p53 gene alterations and reduced pl4 (ARE) expression both correlate with poor prognosis./ Pathol. 2005 207 410-421. 

Hisaoka M, Tsuji S, Morimitsu Y, et al. Detection of TLS/FUS-CHOP fusion transcripts in myxoid and round cell liposarcomas by nested reverse RT-PCR using archival paraffin embedded tissue. J Diagn Mol Pathol. 1998 7 96-101. 

Oikawa K, Ishida T, Imamura T, et al. Generation of the novel monoclonal antibody against TLS/EWS-CHOP chimeric oncoproteins that is applicable to one of the most sensitive assays for myxoid and round cell liposarcomas. Am J Surg Pathol. 2006 30 351-356. 

The t(12 16)(ql3 pll) translocation is the most common translocation, described in more than 90% of myxoid and round cell liposarcoma, mainly those arising within the thigh soft tissue. Myxoid liposarcoma arising elsewhere seems to be not related to this specific genetic abnormality. The t(12 16)(ql3 pll) translocation is caused by the fusion of the TLS gene and the CHOP gene. 

Some studies show that there is no significant association between the fusion variant and the tumor behavior but other studies reported that the poorly differentiated round cell type of myxoid liposarcoma is mainly associated with the fusion transcript type 1. 

As the two above-described translocations are specific for myxoid and round cell liposarcoma, they can be used as sensitive molecular markers to distinguish both liposarcoma types from other neoplastic or nonneoplastic lesions with similar morphologic features. This method can be also used for the examination of surgical margins after surgical resection or for the detection of micrometastases. Additionally,... 

NCT00579501 Safety and Efficacy Study of Trabectedin for the Treatment of Localized Myxoid / Round Cell Liposarcoma... 

Table VII Genomics of Myxoid/Round Cell Liposarcoma (MyLSrc)...

Demicco EG, Tiorres KE, Ghadimi MP, Colombo C, Bolshakov S, Hoffman A, Peng T, Bov6e IV, Wang WL, Lev D, Lazar AJ. Involvement of the PI3K/Akt pathway in myxoid/round cell liposarcoma. Mol Pathol. 2012 25 212-21. 

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