This transgene contains a cDNA encoding the human tumor-associated NPM1/ALK fusion protein under control of the regulatory sequences of the human CD2 gene. The chimeric tyrosine kinase, comprising the N-terminal 40% of the ubiquitously expressed protein nucleophosmin (nucleolar phosphoprotein B23, numatrin) (NPM1) joined to the entire cytoplasmic tail of anaplastic lymphoma kinase (ALK), is expressed in human tumors from a fusion gene resulting from the t(2;5)(p23;q35) chromosomal translocation that is present in 40-50% of anaplastic large cell lymphomas. The NPM1/ALK cDNA was inserted into a CD2 expression cassette that includes 5 kb of 5' flanking sequence containing the promoter, transcription initiation site and first intron; and 5.5 kb of 3' flanking sequence containing the two polyadenylation signals and locus control region (LCR) of the human CD2 gene. Expression of the mRNA is detected by reverse transcription/polymerase chain reaction (RT-PCR) analysis and of the chimeric protein by western blot analysis only in tumors, and not in pre-cancerous thymocytes, of transgenic animals.