07. CLINICAL LAB. DIAGNOSTICS OF HEMOBLASTOSIS.ppt

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CLINICAL LABORATORY DIAGNOSTICS OF HEMOBLASTOSISKrynytska Inna Yakivna

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Today’s Lecture1. Introduction to Leukemias. 2. Acute Leukemias. 3. Chronic Leukemias

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Definition of Leukemia Leukemia is a malignant disease characterized by unregulated proliferation of one cell type.(one clone of Immature cell) It may involve any of the cell lines or a stem cell common to several cell lines. Leukemias are classified into 2 major groups Chronic in which the onset is insidious, the disease is usually less aggressive, and the cells involved are usually more mature cells Acute in which the onset is usually rapid, the disease is very aggressive, and the cells involved are usually poorly differentiated with many blasts.

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TypesBoth acute and chronic leukemias are further classified according to the prominent cell line involved in the expansion: If the prominent cell line is of the myeloid series it is a myelocytic leukemia (sometimes also called granulocytic) If the prominent cell line is of the lymphoid series it is a lymphocytic leukemia Therefore, there are four basic types of leukemia Acute myelocytic leukemia – AML- (includes myeloblastic, promyelocytic, monocytic, myelomonocytic, erythrocytic, and megakaryocytic) Acute lymphocytic leukemia – ALL- (includes T cell, B cell, and Null cell) Chronic myelocytic leukemia – CML - (includes myelocytic and myelomonocytic)

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Acute & Chronic TypesChronic lymphocytic leukemia – CLL - (includes plasmocytic {multiple myeloma}, Hairy cell, prolymphocytic, large granular cell lymphocytic, Sezary’s syndrome, and circulating lymphoma) Etiology – the exact cause is frequently not known, but predisposing factors are known: Host factors Some individuals have an inherited increased predisposition to develop leukemia There is an increased incidence in those with an inherited tendency for chromosome fragility or abnormality or those with increased numbers of chromosomes (such as Down’s syndrome). Many of these diseases are characterized by chromosomal translocations.

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Incidence of leukemiaThere is an increased incidence in those with hereditary immunodeficiencies. There is an increased incidence in those with chronic marrow dysfunction such as those with myeloproliferative diseases, myelodysplastic syndromes, aplastic anemia, or paroxsymal nocturnal hemoglobinuria. Environmental factors: Exposure to ionizing radiation Exposure to mutagenic chemicals and drugs Viral infections

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Incidence of leukemiaIncidence Acute leukemias can occur in all age groups ALL is more common in children AML is more common in adults Chronic leukemias are usually a disease of adults CLL is extremely rare in children and unusual before the age of 40 CML has a peak age of 30-50

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Comparison Acute Vs ChronicComparison of acute and chronic leukemias: Acute Chronic Age all ages usually adults Clinical onset sudden insidious Course (untreated) 6 mo. or less 2-6 years Leukemic cells immature >30% blasts more mature cells Anemia prominent mild Thrombocytopenia prominent mild WBC count variable increased Lymphadenopathy mild present;often prominent Splenomegaly mild present;often prominent

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. Acute leukemia Acute leukemia – Is a result of: Malignant transformation of a stem cell leading to unregulated proliferation and Arrest in maturation at the primitive blast stage. Remember that a blast is the most immature cell that can be recognized as committed to a particular cell line. Clinical features Leukemic proliferation, accumulation, and invasion of normal tissues, including the liver, spleen, lymph nodes, central nervous system, and skin, cause lesions ranging from rashes to tumors.

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Evaluation of leukemiaFailure of the bone marrow and normal hematopoiesis may result in pancytopenia with death from hemorrhaging and infections. Lab evaluation The lab diagnosis is based on two things Finding a significant increase in the number of immature cells in the bone marrow including blasts, promyelocytes, promonocytes (>30% blasts is diagnostic) Identification of the cell lineage of the leukemic cells

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Evaluation of leukemiaPeripheral blood: Anemia (normochromic, normocytic) Decreased platlets Variable WBC count The degree of peripheral blood involvement determines classification: Leukemic – increased WBCs due to blasts Subleukemic – blasts without increased WBCs Aleukemic – decreased WBCs with no blasts Classification of the immature cells involved may be done by:

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Cell Morphology in LeukemiaMorphology – an experienced morphologist can look at the size of the blast, the amount of cytoplasm, the nuclear chromatin pattern, the presence of nucleoli and the presence of auer rods (are a pink staining, splinter shaped inclusion due to a rod shaped alignment of primary granules found only in myeloproliferative processes) to identify the blast type: AML – the myeloblast is a large blast with a moderate amount of cytoplasm, fine lacey chromatin, and prominent nucleoli. 10-40% of myeloblasts contain auer rods.

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Myeloid maturationMATURATIONAdapted and modified from U Va website

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Myeloblasts with auer rods

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LymphoblastsALL – in contrast to the myeloblast, the lymphoblast is a small blast with scant cytoplasm, dense chromatin, indistinct nucleoli, and no auer rods

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Lymphoblast

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AML

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Auer rods in AML

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ALL

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CytochemistryCytochemistry – help to classify the lineage of a leukemic cell (myeloid versus lymphoid) Myeloperoxidase – is found in the primary granules of granulocytic cells starting at the late blast stage. Monocytes may be weakly positive.

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Sudan blackSudan black stains phospholipids, neutral fats and sterols found in primary and secondary granules of granulocytic cells and to a lesser extent in monocytic lysosomes. Rare positives occur in lymphoid cells

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Nonspecific EsteraseNonspecific esterase – is used to identify monocytic cells which are diffusely positive. T lymphocytes may have focal staining

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Acid phosphataseAcid phosphatase may be found in myeloblasts and lymphoblasts. T lymphocytes have a high level of acid phosphatase and this can be used to help make a diagnosis of acute T-lymphocytic leukemia.

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Leukocyte Alkaline phosphataseLeukocyte alkaline phosphatase – is located in the tertiary granules of segmented neutrophils, bands and metamyelocytes. The LAP score is determined by counting 100 mature neutrophils and bands. Each cell is graded from 0 to 5. The total LAP score is calculated by adding up the scores for each cell.

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Leukocyte alkaline phosphatase

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Immunologic markersImmunologic markers (immunophenotyping) – these are used mainly for lymphocytes, i.e., for determining B cell or T cell lineage. These tests rely on antibodies made against specific surface markers. (Fluorescent Antibody Tagging) flow cytometer that will determine the number of cells that have a fluorescent tag and which are thus positive for the presence of the surface marker to which the primary antibody was made.

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Last Updated: 8th March 2018

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