Diagnosing ALL begins with a thorough medical history, physical examination, complete blood count, and blood smears. While many symptoms of ALL can be found in common illnesses, persistent or unexplained symptoms raise suspicion of cancer. Because many features on the medical history and exam are not specific to ALL, further testing is often needed. A large number of white blood cells and lymphoblasts in the circulating blood can be suspicious for ALL because they indicate a rapid production of lymphoid cells in the marrow. The higher these numbers typically point to a worse prognosis. While white blood cell counts at initial presentation can vary significantly, circulating<unk> ells are seen on peripheral blood smears in the majority of cases. A bone marrow biopsy provides conclusive proof of ALL, typically with >20% of all cells being leukemic lymphoblasts. A lumbar puncture (also known as a spinal tap) can determine whether the spinal column and brain have been invaded. Brain and spinal column involvement can be diagnosed either through confirmation of leukemic cells in the lumbar puncture or through clinical signs of CNS leukemia as described above. Laboratory tests that might show abnormalities include blood count, kidney function, electrolyte, and liver enzyme tests. Pathological examination, cytogenetics (in particular the presence of Philadelphia chromosome), and immunophenotyping establish whether the leukemic cells are myeloblastic (neutrophils, eosinophils, or basophils) or<unk>  (B lymphocytes or T lymphocytes). Cytogenetic testing on the marrow samples can help classify disease and predict how aggressive the disease course will be. Different mutations have been associated with shorter or longer survival. Immunohistochemical testing may reveal TdT or CALLA antigens on the surface of leukemic cells. TdT is a protein expressed early in the development of pre-T and pre-B cells, whereas CALLA is an antigen found in 80% of ALL cases and also in the "blast crisis" of CML. Medical imaging (such as ultrasound or CT scanning) can find invasion of other organs commonly the lung, liver, spleen, lymph nodes, brain, kidneys, and reproductive organs. File:ALL - Peripherial Blood - Diagnosis - 01.acute<unk>  leukemia (ALL), peripheral blood of a child, Pappenheim stain, magnification x100 File:ALL-KM-2.bone marrow smear (large magnification) from a person with<unk>  File:ALL-KM-3.bone marrow smear from a person with<unk>  Immunophenotyping In addition to cell morphology and cytogenetics, immunophenotyping, a laboratory technique used to identify proteins that are expressed on their cell surface, is a key component in the diagnosis of ALL. The preferred method of immunophenotyping is through flow cytometry. In the malignant lymphoblasts of ALL, expression of terminal deoxynucleotidyl transferase (TdT) on the cell surface can help differentiate malignant lymphocyte cells from reactive lymphocytes, white blood cells that are reacting normally to an infection in the body. On the other hand, myeloperoxidase (MPO), a marker for the myeloid lineage, is typically not expressed. Because precursor B cell and precursor T cells look the same, immunophenotyping can help differentiate the subtype of ALL and the level of maturity of the malignant white blood cells. The subtypes of ALL as determined by immunophenotype and according to the stages of maturation. B cell Lineage T cell Lineage pre-pre-B ALL (pro-B-ALL) precursor T- ALL common ALL mature T-cell ALL pre-B ALL mature B-cell ALL (Burkitt leukemia – FAB L3) An extensive panel of monoclonal antibodies to cell surface markers, particularly CD or cluster of differentiation markers, are used to classify cells by lineage. Below are immunological markers associated with B cell and T cell ALL. Immunological Markers B cell Lineage T cell Lineage B cell Lineage CD19, CD22, CD79a + − CD10 − or + (common ALL) cytoplasmic Ig − or + (pre-B ALL) surface Ig − or + (mature B-cell ALL) TdT + + T cell Lineage CD2, CD3, CD4, CD5, CD7, CD8 − + TdT + + Cytogenetics Cytogenetic analysis has shown different proportions and frequencies of genetic abnormalities in cases of ALL from different age groups. This information is particularly valuable for classification and can in part explain the different prognoses of these groups. In regards to genetic analysis, cases can be stratified according to ploidy, a number of sets of chromosomes in the cell, and specific genetic abnormalities, such as translocations. Hyperdiploid cells are defined as cells with more than 50 chromosomes, while hypodiploid are defined as cells with less than 44 chromosomes. Hyperdiploid cases tend to carry a good prognosis while hypodiploid cases do not. For example, the most common specific abnormality in childhood<unk>  is the t(12;21) ETV6-RUNX1 translocation, in which the RUNX1 gene, encoding a protein involved in transcriptional control of hemopoiesis, has been translocated and repressed by the ETV6-RUNX1 fusion protein. Below is a table with the frequencies of some cytogenetic translocations and molecular genetic abnormalities in ALL. Cytogenetic translocation Molecular genetic abnormality % cryptic t(12;21) TEL–AML1 fusion 25.4% t(1;19)(q23;p13) E2A–PBX (PBX1) fusion 4.8% t(9;22)(q34;q11) BCR-ABL fusion(P185) 1.6% t(4;11)(q21;q23) MLL–AF4 fusion 1.6% t(8;14)(q24;q32) IGH-MYC fusion t(11;14)(p13;q11) TCR–RBTN2 fusion Classification French-American-British Historically, prior to 2008, ALL was classified morphologically using the French-American-British (FAB) system that heavily relied on morphological assessment. The FAB system takes into account information on size, cytoplasm, nucleoli, basophilia (color of cytoplasm), and vacuolation (bubble-like properties). FAB Subtype Cell Type Characteristics Comments ALL - L1 T cell or pre-B cell Small and homogeneous (uniform) cells ALL - L2 T cell or pre-B cell Large and heterogeneous (varied) cells ALL - L3 B cell Large and varied cells with vacuoles Mature B-cell ALL also named Burkitt leukemia. Typically, poor prognosis with standard therapy While some clinicians still use the FAB scheme to describe tumor cell appearance, much of this classification has been abandoned because of its limited impact on treatment choice and prognostic value. World Health Organization In 2008, the World Health Organization classification of<unk>  was developed in an attempt to create a classification system that was more clinically relevant and could produce meaningful prognostic and treatment decisions. This system recognized differences in genetic, immunophenotype, molecular, and morphological features found through cytogenetic and molecular diagnostics tests. This subtyping helps determine the prognosis and the most appropriate treatment for each specific case of ALL. The WHO subtypes related to ALL are: *B-lymphoblastic leukemia/lymphoma * Not otherwise specified (NOS) * with recurrent genetic abnormalities * with t(9;22)(q34.1;q11.2);BCR-ABL1 * with t(v;11q23.3);KMT2A rearranged * with t(12;21)(p13.2;q22.1); ETV6-RUNX1 * with t(5;14)(q31.1;q32.3) IL3-IGH * with t(1;19)(q23;p13.3);TCF3-PBX1 * with hyperdiploidy * with hypodiploidy * T-lymphoblastic leukemia/lymphoma *<unk>  leukemias of ambiguous lineage *<unk>  undifferentiated leukemia *Mixed phenotype<unk>  leukemia (MPAL) with t(9;22)(q34.1;q11.2); BCR-ABL1 * MPAL with t(v;11q23.3); KMT2A rearranged * MPAL, B/myeloid, NOS * MPAL, T/myeloid, NOS
Acute lymphoblastic leukemia
Aplastic anemia
Acute myeloid leukemia
Infectious mononucleosis
Prolymphocytic leukemia
Lymphoid leukemia
Myeloid leukemia
Chronic lymphocytic leukemia