BCR and B-cell chronic lymphocytic leukemia: However, the children (≤14 years old) had the highest percentage of precurso B-cell lymphoblastic leukemia cases (36.6%), and precursor cell lymphoblastic leukemia-NOS s (31.4%), while cases of B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma and chronic myelogenous leukemia (BCR/ABL positive) were the lowest percentage (0.1%).