ATM and B-cell chronic lymphocytic leukemia: FISH analysis of the four-probe set from Dohner’s hierarchical model is considered the gold standard for cytogenetic evaluation in CLL (10, 20), with five prognostic categories: the poorest prognosis is associated with a 17p deletion (TP53 gene), followed by an 11q22.3 deletion (ATM gene), trisomy 12 and normal FISH results.