In the old FAB classification systems, leukemia and lymphoma were a point of initial differentiation. A disease was called a lymphoma if it was initially or mostly affecting the lymphatic system (lymph nodes, spleen, etc.), although it could spread to the bone marrow and blood. The disorder was termed leukemia if the major site was the bone marrow and blood, although it could also affect the lymphatic system.
However, in the WHO classification, the initial differentiation is based on whether the lineage is that of a B cell or T cell which can be determined by cell surface markers using flow cytometry.
The WHO classification of acute lymphoblastic leukemia was revised in 2016, and includes the following types described in Table 10.
Table 10. WHO Classification of Acute Lymphoblastic Leukemia.| Category | Subcategory |
| B-cell lymphoblastic leukemia/lymphoma, not otherwise specified | |
| B-cell lymphoblastic leukemia/lymphoma with recurrent genetic abnormalities | B-cell lymphoblastic leukemia/lymphoma with hypodiploidy |
| B-cell lymphoblastic leukemia/lymphoma with hyperdiploidy |
| B-cell lymphoblastic leukemia/lymphoma with t(9;22)(q34;q11.2)[BCR-ABL-1] |
| B-cell lymphoblastic leukemia/lymphoma with t(v;11q23)[MLL rearranged] |
| B-cell lymphoblastic leukemia/lymphoma with t(12;21)(p13;q22)[ETV6-RUNX-1] |
| B-cell lymphoblastic leukemia/lymphoma with t(1;19)(q23;p13.3)[ZTCZX3-PBX1] |
| B-cell lymphoblastic leukemia/lymphoma with t(5;14)(q31;q32)[IL-3IGH] |
| B-cell lymphoblastic leukemia/lymphoma with intrachromosomal amplification of chromosome 21 (iAMP21) |
| B-cell lymphoblastic leukemia/lymphoma with translocations involving tyriosine kinases or cytokine receptors (BCR-ABL1-like ALL) |
| T-cell lymphoblastic leukemias/lymphomas | Early T-cell precursor lymphoblastic leukemia |
Notice that some of the chromosomal and genetic changes are similar to those seen in AML.
The image on the right is of a B Cell lymphoblastic leukemia.
