Genomic alterations

Cytogenetic studies of these tumors have demonstrated the recurrent translocation t(11;22)(p13;q12), which has been characterized as a fusion of the WT1 and EWSR1 genes.[105,108] The EWSR1::WT1 fusion confirms the diagnosis of desmoplastic small round cell tumor. The average tumor variant burden is low for desmoplastic small round cell tumor (<1 variant per megabase), and recurring gene alterations other than the EWSR1::WT1 fusion are uncommon.[109] A small percentage of cases (approximately 3%) have activating variants in FGFR4, with amplification of FGFR4 observed at similar frequency.[109,110] Inactivating variants in TP53 and ARID1A are observed in a small percentage of desmoplastic small round cell tumor cases.[109,110]