MLS is a translocation-related sarcoma, and over 90% of MLS cases are characterized by the chromosomal translocation t (12;16) (q13;p11), resulting in the fusion of the FUS (Fused In Sarcoma) and DDIT3 (DNA damage-inducible transcript 3) genes at 12q13 and 16p11 to form the fusion gene FUS::DDIT3 and to produce the FUS::DDIT3 fusion protein [4,5] (Figure 1A), although the relationship between FUS::DDIT3 and the round-cell components in MLS has not been found. The gene discussed is FUS; the disease is sarcoma.