A cDNA clone was produced using RNA purified from a confirmed "clear cell sarcoma" tumor. The cDNA contained the EWSR1/ATF1 fusion product of the t(12;22) chromosomal translocation typical of these tumors. This cDNA was inserted downstream of a floxed pgk-neomycin cassette and upstream of an IRES-EGFP. Stop codons in the neomycin cassette prevent EWSR1/ATF1 and EGFP expression.