Ewing sarcoma with ERG gene rearrangements: A molecular study focusing on the prevalence of FUS‐ERG and common pitfalls in detecting EWSR1‐ERG fusions by FISH

Abstract

The genetics of Ewing sarcoma (ES) are characterized by a canonical fusion involving EWSR1 gene and a member of the ETS family of transcription factors, such as FLI1 and ERG. In fact, ERG gene rearrangements represent the second most common molecular alteration, with EWSR1-ERG being identified in 5–10% of cases, while only a handful of reports document a FUS-ERG fusion. In this study, we focus on ES with ERG gene abnormalities, specifically to investigate the prevalence and clinicopathologic features of FUS-ERG fusions in a large cohort of small blue round cell tumors (SBRCTs) and compare to the eight reported FUS-positive ES. Among the 85 SBRCTs tested, seven (8.2%) cases harbored FUS gene rearrangements; six fused to ERG and one with FEV. During this investigation we came across a number of ERG-rearranged ES lacking both EWSR1 and FUS abnormalities by FISH. In one case, RNA sequencing identified an EWSR1-ERG transcript despite the negative EWSR1 rearrangements by FISH. Additional 3-color FISH fusion assay demonstrated the fusion of EWSR1 and ERG signals in all four cases negative for break-apart EWSR1 FISH. These results emphasize a potential pitfall of relying on EWSR1 FISH assay alone for diagnosis of ES. In cases with classic morphology and/or strong CD99 and ERG immunoreactivity, additional molecular testing should be applied, such as ERG FISH or RT-PCR/next generation sequencing, for a more definitive diagnosis. Although our study group is small, there were no differences noted between the clinical, morphologic features and immunoprofile of the different subsets of ERG-rearranged SBRCTs.

Effective molecular targeting of CDK4/6 and IGF-1R in a rare FUS-ERG fusion CDKN2A-deletion doxorubicin-resistant Ewing's sarcoma patient-derived orthotopic xenograft (PDOX) nude-mouse model

“…There are over 50 known histological sub-types of sarcoma. Ewing's sarcoma is a rare malignancy in which EWS-FLI1 is considered to be the causal translocation for 90% of cases [1]. Treatment for Ewing's sarcoma uses surgery, radiation, and chemotherapy but with poor outcome.…”

“…In the present study, a Ewing's sarcoma patient with both FUS-ERG fusion [1, 32] and CDKN2A/B loss was studied. No patient with both these genetic alterations has been previously reported.…”

Combining Tumor-Selective Bacterial Therapy with <b><i>Salmonella typhimurium</i></b> A1-R and Cancer Metabolism Targeting with Oral Recombinant Methioninase Regressed an Ewing’s Sarcoma in a Patient-Derived Orthotopic Xenograft Model

“…To realize precision therapy for ES patients, we previously established a patient-derived orthotopic xenograft (PDOX) model of a rare ES tumor with both a FUG-ERG fusion and a loss of the cyclin-dependent kinase inhibitor 2A/B (CDKN2A/B) [7, 8]. Previously, we found optimal drugs for the bone marrow recurrence of this patient using the ES PDOX model [9, 10].…”

Head and Neck Round Cell Sarcomas: A Comparative Clinicopathologic Analysis of 2 Molecular Subsets: Ewing and CIC-Rearranged Sarcomas

“…Only cases that had either previous molecular confirmation or had available material for further molecular work-up were included in this study. The molecular confirmation of ES was based either on RT-PCR evidence of an EWSR1-FLI1/ERG fusion transcript or an EWSR1/FUS gene rearrangement by FISH, as previously described [10]. For CIC-rearranged sarcomas (CRS), the diagnosis was confirmed by CIC gene rearrangement by FISH, followed by further FISH-fusion assay investigation to determine a CIC-DUX4 fusion [13].…”

“…Ewing sarcoma (ES) is the prototypical round cell sarcoma characterized by pathognomonic gene fusions between the EWSR1 gene and member of the ETS transcription factor family (FLI1, ERG, ETV1, ETV4, or FEV) [1][2][3][4][5][6] and less commonly to a non-ETS family gene, such as NFATc2 [7]. In rare examples of ES, FUS gene can substitute for EWSR1 in the fusion, retaining a similar phenotype [8][9][10]. Other round cell sarcomas with specific translocations include alveolar rhabdomyosarcoma, myxoid/round cell liposarcoma, desmoplastic small round cell tumor and poorly differentiated monophasic synovial sarcomas.…”