Immunohistochemistry revealed that the blasts had detectable ICN1 (Fig. 5B), Sanger sequencing of DNA prepared from leukemic blasts confirmed that the tumor maintained the same genotype (data not shown), and flow cytometry confirmed an immunophenotype consistent with ETP-ALL, as the blasts were CD45(dim), CD34+, HLA-DR+, CD3+, CD5+, CD7+, CD13+, and CD33+. This evidence concerns the gene PTPRC and acute lymphoblastic leukemia.