Molecular diagnostics and immunophenotyping have become the basis for targeted therapy in ALL, as demonstrated by the use of tyrosine kinase inhibitors for BCR-ABL1-positive ALL, and rituximab for CD20-positive B-cell precursor ALL [16] or mature B-ALL/Burkitt lymphoma [19], which improved the prognosis of these previously highly adverse subtypes. Here, MS4A1 is linked to precursor B-cell acute lymphoblastic leukemia.