This difference can be explained by the fact that pro-B ALL is the most frequent leukemia in children aged <1 year, and it is less common in older children and adults.(5) Pro-B ALL is characterized by negative CD10, and its most frequent molecular alteration is KMT2A t(4;11) rearrangement; this subtype has an unfavorable prognosis.(49,50) The frequency of negative CD10 in B-cell ALL cases was 8.3%, close to 11.36%, as reported by Haddad et al.(11). This evidence concerns the gene MME and leukemia.