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==Genetic Diagnostic Testing Methods==

==Genetic Diagnostic Testing Methods==

Ancillary studies such as immunohistochemistry and molecular tests are useful in differentiating soft tissue tumors. SFTs have historically been diagnosed by morphology and strong diffuse CD34 positivity. Additional immunohistochemical phenotype previously used for identification included expression of Bcl2, CD99, and vimentin and absence of expression of epithelial, muscle, and neural markers. However, the introduction of STAT6 (signal transducer and activator of transcription 6) immunostain now dominates due to its high sensitivity and specificity. STAT6 expression is demonstrated by nuclear staining. Molecular testing by next generation sequencing (NGS)-based mRNA sequencing is also highly useful in detecting the NAB2::STAT6 fusion. Breakapart fluorescence in situ hybridization (FISH) probe for STAT6 can detect rearrangement of this gene.  In the context of SFT, the rearrangement of the ''STAT6'' gene is highly suggestive for the presence of ''NAB2-STAT6'' fusion. [https://pubmed.ncbi.nlm.nih.gov/27802414/ A dual color dual fusion probe targeting both genes would be a direct confirmation for ''NAB2-STAT6'' fusion.]

Ancillary studies such as immunohistochemistry and molecular tests are useful in differentiating soft tissue tumors. SFTs have historically been diagnosed by morphology and strong diffuse CD34 positivity. Additional immunohistochemical phenotype previously used for identification included expression of Bcl2, CD99, and vimentin and absence of expression of epithelial, muscle, and neural markers. However, the introduction of STAT6 (signal transducer and activator of transcription 6) immunostain now dominates due to its high sensitivity and specificity. STAT6 expression is demonstrated by nuclear staining. Next generation sequencing (NGS) using mRNA is also highly useful in detecting the NAB2::STAT6 fusion. Breakapart fluorescence in situ hybridization (FISH) probe for STAT6 can detect rearrangement of this gene.  In the context of SFT, the rearrangement of the ''STAT6'' gene is highly suggestive for the presence of ''NAB2-STAT6'' fusion. [https://pubmed.ncbi.nlm.nih.gov/27802414/ A dual color dual fusion probe targeting both genes would be a direct confirmation for ''NAB2-STAT6'' fusion.]

==Familial Forms==

==Familial Forms==

Not Applicable

Not Applicable