Using single single-cell RNA-seq (scRNA-Seq) and proteomics, a recent paper has alluded to the existence of cellular heterogeneity present in the pre-BCR developmental pathway that could lead to distinct subsets of pre-BCR subtypes in B-cell acute lymphoblastic leukemia (B-ALL) [44]. This evidence concerns the gene BCR and precursor B-cell acute lymphoblastic leukemia.