The t(12;21) is virtually undetectable by routine cytogenetics, but the chimeric transcript ETV6-AML1 has been detected in childhood ALL by molecular techniques in up to 36% of cases, making it the most common genetic abnormality in these patients.     ///    "ETV6-AML1 expression defined a subgroup of patients characterised by an age of between two and 12 years, B-lineage immunophenotype and non-hyperdiploid DNA content. "