Discovery of two novel EWSR1/ATF1 transcripts in four chimerical transcripts-expressing clear cell sarcoma and their quantitative evaluation

Abstract The most common recurrent translocation in clear cell sarcoma t(12;22)(q13;q12) results in an EWSR1/ATF1 chimeric gene. We present a molecular analysis of tumor overgrowing right proximal tibia with bone destruction metastatic to two groin lymph nodes. Fluorescent in situ hybridization analysis performed on paraffin-embedded tissue sections of primary tumor sample indicated one rearranged locus of EWSR1 gene and one additional red signal. Reverse transcription-polymerase chain reaction analysis revealed the presence of four different EWSR1 / ATF1 chimerical transcripts in the tumor sample as well as in both metastatic lymph nodes. Two previously described transcripts EWSR1exon7/ATF1exon5 and EWSR1exon8/ATF1exon4 , and two novel transcripts EWSR1exon7 / ATF1exon4 and EWSR1exon9 / ATF1exon4 were identified. Both novel transcripts were out-of-frame fusions and, therefore, most likely had limited biological impact in oncogenesis of clear cell sarcoma. Quantitative evaluation demonstrated unequal distribution of these transcripts, with EWSR1exon8/ATF1exon4 type being overexpressed.