Diagnosis of acute lymphoblastic leukemia

Diagnosis of acute lymphoblastic leukemia is based on the history, physical examination and laboratory studies.

Laboratory diagnostics

General blood count: the number of white blood cells can be normal, reduced or elevated; often, though not always, they reveal blast cells; hyporegenerative normochromic anemia and thrombocytopenia are characteristic.

Biochemical blood test: characterized by an increase in LDH activity; also determine the indicators of kidney and liver function.

Myelogram: bone marrow puncture should be performed at a minimum of two points (in children under 2 years old it is the heel bone or tuberosity of the tibia, in older children - the posterior and anterior awns of the iliac bones) for the collection of a sufficient amount of diagnostic material. It is desirable to take a material intake under general anesthesia. It is necessary to make 8-10 smears from each point, and also collect material for immunophenotyping, cytogenetic and molecular-genetic studies.

Spinal puncture is an obligatory diagnostic measure performed by a specialist in sedation and in the presence of platelets in the peripheral blood in an amount of not less than 30,000 in μl (if necessary, transfusions of platelet mass are performed prior to puncture). To prepare a cytopreparation, at least 2 ml of cerebrospinal fluid is necessary.

Instrumental diagnostics

It is desirable (and if there is neurological symptomatology - necessarily) CT of the brain.

Ultrasound examination allows to determine the size of infiltrated parenchymatous organs and enlarged lymph nodes of the abdominal cavity, small pelvis and retroperitoneal space, the size and structure of the testicles.

Radiography of the chest can detect an increase in the mediastinum, exudative pleurisy. Radiography of bones and joints is performed according to the indications.

To clarify the diagnosis and exclude heart disease, conduct electrocardiography and echocardiography. Consultations of the oculist, the otorhinolaryngologist (examination of an eye bottom, adnexal sinuses of a nose) are shown.

Special diagnostic methods

Diagnosis of acute lymphoblastic leukemia is based on evaluation of the tumor substrate - bone marrow, cerebrospinal fluid.

Cytological examination of the bone marrow allows to detect hypercellularity, narrowing of germs of normal hematopoiesis and infiltration by powerful cells - from 25% to total replacement of bone marrow with a tumor.

Morphological similarity of malignant lymphoblasts and normal progenitor cells requires the determination of the percentage of lymphoblasts in bone marrow smears stained according to Romanovsky-Giemsa. The morphological classification of acute lymphoblastic leukemia, according to the criteria of the FAB group (Franco-American-British Cooperative Group), provides for the subdivision of blasts into groups L1, L2 and L3, based on the size, structure of the nucleus, presence of inclusions and other signs More than 90% of cases of acute lymphoblastic leukemia children are referred to option L1, 5-15% to L2, less than 1% to L3. Currently, acute leukemia with a mature B phenotype (L3) is referred to the group of non-Hodgkin's lymphomas (this option is not considered in this section).

Cytochemical research is the next mandatory stage of diagnosis. With the help of cytochemical staining, the membership of cells to a certain line of differentiation is revealed. Mandatory staining for myeloperoxidase (the reaction of cells belonging to the lymphoid line of differentiation is negative). The Schick reaction to glycogen helps differentiate lymphoid blasts due to the characteristic granular staining of the cytoplasm. Color Sudan black is positive in myeloid cells with a typical arrangement of granules. Acid phosphatase is detected in T-cell leukemia.

Immunophenotyping is one of the main research that determines the cellularity of the blast population and the prognosis of the disease. Specific surface and cytoplasmic antigens of T and B lymphocytes are used as markers for identification, determination of origin and stage of differentiation of lymphoid cells. Using a panel of monoclonal antibodies to differentiation clusters and determining the percentage of their expression in an authoritative population allows one to indicate whether the leukemia clone in a given patient belongs to the T or B line. The results of immunophenotyping of imperious cells, according to modern classification, are based on the diagnosis of acute lymphoblastic leukemia.

Cytogenetic and molecular genetic methods have been widely used in recent years to study leukemia cells. The methods allow to assess the state of the chromosome apparatus - the number of chromosomes and their structural changes (translocations, inversions, deletions). Cytogenetic abnormalities and DNA index (the ratio of the amount of DNA in leukemic cells and in cells with a normal diploid karyotype) are significant prognostic factors. Detection of clonal anomalies characteristic for tumor cells of this patient allows one to track the number of these cells in the dynamics of the disease at the molecular genetic level and determine the minimal residual cell population. Identification and molecular characterization of genes, the regulation or function of which can be damaged as a result of chromosomal changes, contributes to an understanding of the molecular basis of malignant transformation.

An important prognostic factor is the evaluation of minimal residual disease. That is, an estimate of the amount of residual leukemia cells in a patient in remission. The technique for detecting a minimal residual disease lies in the determination of cells with karyotype anomalies using cytogenetic methods (one abnormal cell per 100 normal cells can be detected) or a polymerase chain reaction (PCR allows one pathological cell of 10 ⁵ normal cells to be detected ). A very sensitive method is flow cytofluorimetry, which allows detecting cells with an abnormal immunophenotype. A high level of minimal residual disease after remission induction or before maintenance therapy correlates with poor prognosis.

Prognostic factors of the outcome of acute lymphoblastic leukemia therapy

Factors	Favorable outlook	Adverse forecast
Age	Older than 1 year and under 9 years	Younger than 1 year and older than 9 years
Floor	Women's	Male
Leukocytosis	<50 000 in μL	> 50,000 volts
DNA Index	> 1.16	<1.16
The number of chromosomes in imperious cells	> 50	<45 (especially 24-38)
Response to the 8th day of treatment	No blasts in the blood	There are blasts in the blood
CNS-status	CNS1	CNS 2 or CNS 3
Cytogenetics	Trisomy (+4) or (+10)	T (4; 11), t (9; 22)
Molecular Genetics	TEL / AML1	MLL Re-Arrangement
Immunophenotype	B-precursors	T-cell

• CNS is the central nervous system.
• DNA - deoxyribonucleic acid.
• CNS 1 - absence of blast cells in CSF.
• CNS 2 - blast cells in CSF in the absence of cytosis (<5 cells in μL).
• CNS 3 - blast cells and cytosis in CSF (£ 5 cells in μL).

Neuroleukemia

Leukemic cells can enter the central nervous system from the systemic blood stream, through migration through the venous endothelium and from petechial hemorrhage (deep thrombocytopenia at the time of diagnosis is associated with a high incidence of neuronal leukemia). According to an alternative hypothesis, leukemia cells can spread directly from the bone marrow of the skull bones to the subdural space and further to the central nervous system for venen adventitia and nerve shells. Knowledge of the specific mechanism of cell penetration can have a clinical application: in cases of direct penetration of cells from the bone marrow into the CNS, local treatment is most effective, not only cranial irradiation, but also intrathecal administration of chemotherapy drugs. In the case of the spread of leukemia cells from systemic circulation, systemic polychemotherapy plays a greater role. The mechanism of penetration of tumor cells into the CNS depends on the type of leukemia cells, the amount of them in the systemic circulation and the presence of hemorrhagic syndrome, the age of the patient and the maturity of the hemato-encephalic barrier. It is in the central nervous system that the overwhelming majority of tumor cells are outside the mitotic cycle, these cells can persist in the CSF for a very long time - for dozens of years. The presence of just one blast cell in 1 μl of cerebrospinal fluid means that the number of these cells in the entire cerebrospinal space is at least 10 ⁵

[1], [2], [3], [4], [5], [6], [7]