The FUS gene is located on chromosome 16p11.2. The FUS Break Apart FISH probe is designed to label both ends of the FUS gene, respectively. A 700 Kb orange probe is designed at the 3′ end of the FUS gene, and a 800 Kb green probe is designed at the 5′ end of the FUS gene.

Myxoid liposarcomas (MLS) comprise 30% of liposarcomas and 10% of adult soft tissue sarcomas. Round-cell progression indicates poor prognosis. Most cases (95%) show t(12;16) translocation creating FUS-DDIT3 fusion, while 5% have t(12;22) generating EWSR1-DDIT3 fusion. FUS rearrangements also occur in low-grade fibromyxoid sarcoma, limiting specificity for MLS detection.