Gene expression profiling of myxoid liposarcomas (validation set INT-B)

FUS-CHOP and EWS-CHOP balanced translocations characterize myxoid liposarcoma which encompasses myxoid (ML) and round cell (RC) variants initially believed to be distinct diseases. Currently, myxoid and RC liposarcoma are regarded to represent the well differentiated and the poorly differentiated ends, respectively, within spectrum of myxoid liposarcoma where the fusion proteins blocking lipogenic differentiation play a role in tumor initiation while molecular determinants associated to progression to RC remain poorly understood. Activation of AKT pathway sustained by PIK3CA and PTEN mutations and growth factor receptor signalling such as RET and IGF1R have been recently correlated with the increasing of aggressiveness and RC. Aim of the present study is to elucidate molecular events involved in driving round cell progression analyzing two small series of MLS selected to be representative of the two end of the gamut: the pure myxoid (0% of RC component) and RC with high cellular component (≥80%). The validation series (INT-B) consisted of cryopreserved samples obtained from 12 patients. Six cases were pure myxoid and six were pure RC. The diagnoses were confirmed by means of FISH analysis, which revealed CHOP rearrangement, or by RT-PCR searching for the transcript type. Different molecular variants of the fusion transcript have been described by Powers MP et al. (Mod Pathol. 2010).