Diseases of White Blood Cells(3).ppt

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Diseases of White Blood Cells(3)Lecturer :Yiran Ni, MD Department of Pathology China Three Gorges University Email:nyr1986@gmail.comDec.2012

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What we’ve learnedLeukopenia; Reactive leukocytosis; Lymphadenitis; General aspects and classification of neoplastic proliferation of white cell; Acute myeloid leukaemia

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What we’ve learnedMyelodysplastic Syndromes chronic myeloid leukaemia Ph chromosome histiocytoses splenomegaly

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Target of this classLymphoid neoplasms

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DefinitionLymphoid neoplasms encompass a diverse group of entities. In many but not all instances, the phenotype of the neoplastic cell closely resembles that of a particular stage of normal lymphocyte differentiation, a feature that is used in the diagnosis and classification of these disorders.

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DefinitionOne of the confusing aspects of the lymphoid neoplasms concerns the use of the descriptive terms "lymphocytic leukemia and lymphoma. Leukemia is used for lymphoid neoplasms presenting with widespread involvement of the bone marrow, usually accompanied by the presence of large numbers of tumor cells in the peripheral blood. Lymphoma, on the other hand, is used to describe proliferations arising as discrete tissue masses. Traditionally, these terms were attached to what were felt to be distinct entities. However, the line between the "lymphocytic leukemias" and the "lymphomas" often blurs. Many types of "lymphoma" occasionally present with a leukemic peripheral blood picture accompanied by extensive marrow involvement, and evolution to "leukemia" is not unusual during progression of incurable "lymphomas." Conversely, tumors identical to "leukemias" sometimes arise as soft tissue masses without evidence of bone marrow disease. Hence, when applied to particular neoplasms, the terms "leukemia" and "lymphoma" merely describe the usual tissue distribution of the disease at the time of clinical presentation.

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DefinitionLymphoma, on the other hand, is used to describe proliferations arising as discrete tissue masses. Traditionally, these terms were attached to what were felt to be distinct entities. However, the line between the "lymphocytic leukemias" and the "lymphomas" often blurs. Many types of "lymphoma" occasionally present with a leukemic peripheral blood picture accompanied by extensive marrow involvement, and evolution to "leukemia" is not unusual during progression of incurable "lymphomas." Conversely, tumors identical to "leukemias" sometimes arise as soft tissue masses without evidence of bone marrow disease. Hence, when applied to particular neoplasms, the terms "leukemia" and "lymphoma" merely describe the usual tissue distribution of the disease at the time of clinical presentation.

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DefinitionMany types of "lymphoma" occasionally present with a leukemic peripheral blood picture accompanied by extensive marrow involvement, and evolution to "leukemia" is not unusual during progression of incurable "lymphomas."

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DefinitionConversely, tumors identical to "leukemias" sometimes arise as soft tissue masses without evidence of bone marrow disease. Hence, when applied to particular neoplasms, the terms "leukemia" and "lymphoma" merely describe the usual tissue distribution of the disease at the time of clinical presentation.

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LymphomaLymphoma is a neoplasm of lymphocytes, including T and B cells. Primary sites of lymphoma may be lymphoid tissue or any organ of the body.

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The WHO Classification of the Lymphoid NeoplasmsPrecursor B-cell neoplasms (immature B cells) Peripheral B-cell neoplasms (mature B cells) Precursor T-cell neoplasms (immature T cells) Peripheral T-cell and NK-cell neoplasms (mature T cells and natural killer cells) Hodgkin lymphoma (Reed-Sternberg cells and variants).

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The WHO Classification of the Lymphoid Neoplasms

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The WHO Classification of the Lymphoid Neoplasms

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The WHO Classification of the Lymphoid Neoplasms

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ClassificationsWithin the broad group of lymphomas, Hodgkin lymphoma is segregated from all other forms, which constitute the non-Hodgkin lymphomas (NHL). As will be seen, Hodgkin lymphoma is clinically and histologically distinct from the NHLs. In addition, it is treated in a unique fashion, making the differentiation of Hodgkin lymphoma and NHL clinically important.

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ClassificationsThe other important category of lymphoid neoplasms encompasses the plasma-cell neoplasms, tumors composed of terminally differentiated B cells. Such tumors most commonly arise in the bone marrow, only rarely involving lymph nodes or producing a leukemic peripheral blood picture. In addition, as will be seen, much of their patho-physiology is related to the secretion of whole antibodies or immunoglobulin fragments by the tumor cells.

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ClassificationsThe other important category of lymphoid neoplasms encompasses the plasma-cell neoplasms, tumors composed of terminally differentiated B cells. Such tumors most commonly arise in the bone marrow, only rarely involving lymph nodes or producing a leukemic peripheral blood picture. In addition, as will be seen, much of their patho-physiology is related to the secretion of whole antibodies or immunoglobulin fragments by the tumor cells.

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ClassificationsThe clinical presentation of the various lymphoid neoplasms is dictated by the anatomic distribution of disease. Two-thirds of NHLs and virtually all cases of Hodgkin lymphoma present with nontender nodal enlargement (often greater than 2 cm) that can be localized or generalized. The remaining one-third of NHLs arise at extranodal sites (e.g., skin, stomach, or brain).

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ClassificationsIn contrast, the leukemic forms (lymphocytic leukemia) most commonly come to clinical attention owing to signs and symptoms related to suppression of normal hematopoiesis by tumor cells in the bone marrow. Lymphocytic leukemias also characteristically infiltrate and enlarge the spleen and liver. Finally, plasma cell neoplasms involving the skeleton cause local bony destruction and hence often present with pain due to pathologic fractures.

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Our focus will be on the subset of neoplasms listed belowPrecursor B- and T-cell lymphoblastic leukemia/lymphoma; Small lymphocytic lymphoma/chronic lymphocytic leukemia; Follicular lymphomaMantle cell lymphoma Diffuse large B-cell lymphomas; Burkitt lymphoma; Multiple myeloma and related plasma cell dyscrasias Hodgkin lymphoma.

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Principles(1)Before we discuss the specific entities described in the WHO classification, some important principles relevant to the lymphoid neoplasms need to be emphasized. 1. Lymphoid neoplasia can be suspected from the clinical features, but histologic examination of lymph nodes or other involved tissues is required for diagnosis.

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Principles(2)2. Antigen receptor genes rearrange during normal B- and T-cell differentiation through a mechanism that ensures that each developing lymphocyte makes a single, unique antigen receptor. In most lymphoid neoplasms, antigen receptor gene rearrangement precedes transformation; hence, the daughter cells derived from the malignant progenitor share the same antigen receptor gene configuration and sequence and synthesize identical antigen receptor proteins.

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Principles(2)In contrast, normal immune responses are polyclonal and thus comprise populations of lymphocytes expressing many different antigen receptors. As a result, analyses of antigen receptor genes and their protein products can be used to distinguish reactive and malignant lymphoid proliferations. In addition, each antigen receptor gene rearrangement produces a unique DNA sequence that constitutes a highly specific clonal marker that can be used to detect small numbers of residual malignant cells after therapy.

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Principles(3)3. The vast majority of lymphoid neoplasms (80% to 85%) are of B-cell origin, most of the remainder being T-cell tumors; only rarely are tumors of NK origin encountered. Most lymphoid neoplasms resemble some recognizable stage of B- or T-cell differentiation, a feature that is used in their classification.

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Principles(4)4. As tumors of the immune system, lymphoid neoplasms often disrupt normal architecture and function of the immune system, leading to immune abnormalities. Both a loss of vigilance (as evidenced by susceptibility to infection) and breakdown of tolerance (manifested by autoimmunity) can be seen, sometimes in the same patient.

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Principles(4)In a further, ironic twist, patients with inherited or acquired immunodeficiency are themselves at high risk of developing certain lymphoid neoplasms, particularly those caused by oncogenic viruses (e.g., EBV).

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Last Updated: 8th March 2018

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