Advances in sarcoma molecular diagnostics

Abstract

Sarcomas are cancers of mesenchymal origin with the potential to arise in diverse anatomic locations. With over 80 subtypes, which often demonstrate overlapping morphologies, sarcomas frequently require ancillary testing to enable accurate classification. Pathognomonic driver mutations can often be leveraged for diagnostic purposes and include fusion genes, amplification events, and recurrent point mutations.

Expanding the Use of an SS18-SSX Antibody for Molecular Assays in Synovial Sarcoma

“…One significant advantage of using the SS18-SSX antibody is that approximately 95% of all synovial sarcomas harbor the same fusion junction point, regardless of whether - SSX1 or - SSX2 is the 3′ partner 5. This is in contrast with many other translocation-associated sarcomas with multiple partners and/or alternative exonic fusion junction points that would compromise the sensitivity of any single chimeric junction-directed antibody for diagnostic use 27,33. As seen with our negative IHC cases, the antibody facilitates detection of alternative or novel fusion junction sites in synovial sarcoma patients by flagging cases for RNA sequencing.…”

“…Currently, molecular confirmation of a positive diagnosis of synovial sarcoma relies on RNA- or DNA-directed molecular techniques to detect the SS18-SSX fusion transcript and/or the t(X;18) chromosomal translocation. 27 Interphase fluorescence in situ hybridization is commonly used on formalin-fixed, paraffin-embedded samples to identify rearrangements of the SS18 and SSX genes. Further information comes from techniques including RT-PCR (sometimes supported by Sanger sequencing) to identify the involved exons, or by hybrid capture or anchored multiplex sequencing strategies.…”

“…Further information comes from techniques including RT-PCR (sometimes supported by Sanger sequencing) to identify the involved exons, or by hybrid capture or anchored multiplex sequencing strategies. 27 Our lab has developed a NanoString assay designed to specifically identify and quantify the presence of multiple known possible fusion junctions in translocation-associated sarcomas within a single experimental setup. 15 Compared to IHC tests, however, these molecular techniques require relatively expensive equipment, reagents, and trained personnel with sometimes lengthy turnaround.…”

“…Currently, molecular confirmation of a positive diagnosis of synovial sarcoma relies on RNA- or DNA-directed molecular techniques to detect the SS18-SSX fusion transcript and/or the t(X;18) chromosomal translocation 27. Interphase fluorescence in situ hybridization is commonly used on formalin-fixed, paraffin-embedded samples to identify rearrangements of the SS18 and SSX genes.…”

“…Interphase fluorescence in situ hybridization is commonly used on formalin-fixed, paraffin-embedded samples to identify rearrangements of the SS18 and SSX genes. Further information comes from techniques including RT-PCR (sometimes supported by Sanger sequencing) to identify the involved exons, or by hybrid capture or anchored multiplex sequencing strategies 27. Our lab has developed a NanoString assay designed to specifically identify and quantify the presence of multiple known possible fusion junctions in translocation-associated sarcomas within a single experimental setup 15.…”