Representative pathology and schematics of in-frame fusion transcripts. (A) Representative BM histology (original magnification ×400; hematoxylin and eosin stain) (upper panel) and blast morphology on peripheral blood smear (original magnification ×1000; Wright-Giemsa stain) (lower panel) from patient 1. (B) Representative BM histology (original magnification ×400; hematoxylin and eosin stain) (upper panel) and blast morphology on peripheral blood smear (original magnification ×1000; Wright-Giemsa stain) (lower panel) from patient 2. (C) Schematic diagram of the in-frame ETV6-SCFD2 fusion identified in patients 1 and 2. Exon 1 of ETV6 is upstream of exons 5 through 9 of SCFD2, which includes part of the SEC1 domain sequence (exons 4-7). The fusion transcript does not contain the coding sequence for the PNT or ETS domains. (D) Schematic diagram of the in-frame ETV6-CHIC2 fusion identified in patient 3. Exon 1 of ETV6 is upstream of exons 4 through 6 of CHIC2, which includes the distal portion of the ERF4 domain sequence (exons 2-4). As above, the PNT and ETS domains are not included in the fusion transcript. +, positive strand gene; −, negative strand gene.