Among other B-cell markers, B-I and B-II ALL are often CD24 positive and 4G7 (pro- and pre-B surrogate light chain specific MoAb) positive;16 surface CD20 and CD22 are variably positive beyond stage B-I; CD13 and CD33 myeloid/cross lineage antigen can be expressed, as well as the CD34 stem cell antigen, particularly in Ph+ (Philadelphia chromosome-positive) ALL (often B-II with CD34, CD38, CD25 and CD13/33), but myeloid-specific CD117 should not be present and can be used to differentiate further between ALL and rare myeloid leukaemias with negative MPO expression. Here, KIT is linked to acute lymphoblastic leukemia.