Characterization of tumors in the ETV6-mutated kindred. (A) Immunohistochemistry of the DLBCL tumor is consistent with mature B-cell lineage, with expression of CD20 and lack of expression of the immature markers CD34 and TdT and the T-cell marker CD3, which highlights admixed small T cells (original magnification ×40; scale bars, 50 μm). (B) Mutational analysis of WGS data showing distinct ALL and DLBCL mutational spectra of each sample. (C) Gene set enrichment analysis (GSEA) from RNA sequencing of tumor sample showing enrichment of B lymphoid progenitor genes in the B-cell ALL sample (D) and genes expressed in lymphoma in the DLBCL sample. Collectively, the pathologic and genomic features support a true DLBCL in case III.4 rather than a lymphomatous presentation of ALL. Tdt, terminal deoxynucleotidyltransferase.