We found CB leukemias to show mostly mono/oligoclonal TCR rearrangements with G+C+ leukemias tending to express rearranged TCRG and TCRD when of CD4− CD8− (DN) phenotype, and rearranged TCRB when of CD4+ CD8+ (DP) phenotype. Here, TRGC1 is linked to leukemia.