Genomic alterations in young ATLL cases. (A) Recurrent fusions and mutations identified in ATLL cases. The frequencies of each alteration are summarized in the middle panel comparing the current study with the previous study of 304 cases. (B) Validation of CTLA4-CD28 and ICOS-CD28 fusions by reverse transcription–polymerase chain reaction. (C) Schematic representations of CTLA4-CD28 and ICOS-CD28 fusions. C, C-terminal end; Ex, exon; ICOS, inducible costimulator; N, N-terminal end; SP, signal peptide; TM, transmembrane.