Are EWSR1-NFATc2-positive sarcomas really Ewing sarcomas?

Abstract

Recently, Charville et al. [1] reported that EWSR1-rearranged fusion proteins mediate the expression of the pairedbox transcription factor PAX7 in Ewing sarcoma. Based on an analysis of a published gene expression microarray dataset (accession code GSE60740), they state having identified PAX7 to be significantly overexpressed in Ewing sarcoma in comparison to CIC-DUX4-positive round cell sarcomas [1]. In that microarray analysis they compared CIC-DUX4-positive sarcomas with EWSR1-NFATc2-positive sarcomas, assuming that EWSR1-NFATc2-positive sarcomas belong to the family of Ewing sarcomas [1], which are typically characterized by EWSR1-ETS fusion oncogenes [2]. Accordingly, Charville et al. [1] summarized in a schematic EWSR1-FLI1-, EWSR1-ERG-, and EWSR1-NFATc2-positive sarcomas as "Ewing sarcoma," referring to Szuhai et al. (2009) [3], and did not take into account more recent reports in the literature that EWSR1-NFATc2-positive

High Specificity of BCL11B and GLG1 for EWSR1-FLI1 and EWSR1-ERG Positive Ewing Sarcoma

“…Accordingly, in most institutions, the diagnosis of EwS is further validated by molecular pathology techniques, most commonly FISH to detect break-apart events in the EWSR1 gene [24]. Although a positive result is highly sensitive for EwS, some morphological mimics can exhibit break-apart events in the EWSR1 gene (e.g., DSRCT, AFH, and EWSR1-NFATc2-positive sarcomas) [39][40][41].…”

“…Hence, many groups have evaluated several potential diagnostic markers such as FLI1, NKX2-2, and PAX7 that could be used instead of the highly unspecific marker CD99 [40,57,58]. However, to the best of our knowledge, none of these proposed IHC markers completely fulfills the requirements of providing very high sensitivity and specificity for EwS at the same time.…”

“…However, to the best of our knowledge, none of these proposed IHC markers completely fulfills the requirements of providing very high sensitivity and specificity for EwS at the same time. While FLI1 is unable to confirm EwS cases with FET-non-FLI1 translocations [33,59], NKX2-2 and PAX7 lack specificity [60] and can be even strongly expressed in close morphological mimics such as EWSR1-NFATc2-positive sarcomas [40,57,58]. Besides, also Caveolin-1 [54,61], Cyclin-D1 [62], and NR0B1 [63] have been proposed as potential (auxiliary) IHC markers for EwS.…”

“…For instance, PCR analyses may fail to detect all FET-ETS variants unless multiplexed PCRs covering all known variants are employed [35,36]. In addition, fluorescence in situ hybridization (FISH) approaches, commonly used to detect EWSR1 break-apart, can miss EwS cases with FUS-ETS fusions [37], are often challenging in EWSR1-ERG-positive EwS [38], or can be misleading in morphological mimics, such as DSRCT harboring pathognomonic EWSR1-WT1 fusions [24,39,40] or EWSR1-NFATc2 fusion positive small-round-cell sarcomas [40][41][42].…”

PAX7 expression in sarcomas bearing the EWSR1-NFATC2 translocation

“…We thank Dr. Grunewald and colleagues for reading our manuscript [1], and we are happy to respond to their comments. In their letter, Grunewald et al [2] raise the question of whether EWSR1-NFATC2-positive sarcomas really are Ewing sarcomas. They provide information from their interesting publication that appeared in Oncotarget to support the idea that EWSR1-NFATC2-positive sarcomas are transcriptionally distinct from tumors with EWSR1-FLI1 translocation.…”