There are two major populations within this stage. Blasts which are positive for CD19 and CD22, but not for CD10 (and thus very early) are common in infantile leukemia and are prognostically bad. Infantile leukemia is associated with high tumor burden, high white counts, organomegaly and CNS involvement. Those that are positive for CD10 are somewhat later in the lineage; these are termed common ALL (c-ALL) and make up more than half of all ALLs. CNS involvement is infrequent. These have a generally good prognosis.
The correlation of MyAg coexpression, the peculiar chromosomal translocation t(4;11), and poor prognosis in infant pre-pre B ALL has often been suggested.