Hematopoietic and Lymphatic Tissues



Hematopoietic and Lymphatic Tissues


Cells of the hematopoietic and lymphatic tissues serve vital functions of host defense, internal homeostasis, and bodily intactness. They all originate from the same stem cell population and in their functional activities interact in various ways (see chapter 1). Disorders in one cell population may thus cause reactions in the other. For this reason, the hematopoietic and lymphatic systems are discussed together. Just as there are a large number of different cell populations with various differentiation stages and functional activities, so are there a multitude of human diseases of the blood and lymphatic systems. The most common and important are discussed in this chapter. The most common leading symptoms of all these diseases are infection, hemorrhage or thrombosis, and anemia.






Neoplastic Lymphatic Disorders


Malignant neoplasias of the lymphatic tissues are collectively identified as malignant lymphomas (MLs) or, when malignant cells circulate in the blood, lymphocytic leukemias. There are 2 major groups of MLs: Hodgkin lymphomas (lymphogranulomatosis) and non-Hodgkin lymphomas (NHLs). Hodgkin lymphoma, or Hodgkin disease (HD), is distinguished from NHL by its polymorphic features, including certain inflammatory components such as fibrosis and occasional regression simulating nonneoplastic diseases, which eventually may progress to ML. Although it is a lymphatic malignancy, it is accompanied by a large number of associated nonneoplastic cells, which may influence the course and progression of the disease. NHL, by contrast, begins as malignant clonal proliferations. Transition from HD to NHL and combinations of HD with certain types of NHL have been observed (HD and chronic lymphocytic leukemia [CLL] or follicular center cell lymphoma [FCC]; see Table 10-4).


Along with diagnosing an ML as HD or NHL and determining the subclassification based on histologic, immunologic, and cytogenetic markers, staging of disease extent helps to determine the appropriate treatment and the life expectancy of the patient. Staging of all lymphomas is similar: stage I indicates involvement by lymphoma of 1 lymph node site (e.g., axillary, neck); stage II indicates involvement of 2 lymph node sites on the same side of the diaphragm (e.g., neck and axillary, or left and right inguinal); stage III indicates involvement of lymph nodes on both sides of the diaphragm; and stage IV indicates involvement of lymphatic and extralymphatic sites (e.g., liver, spleen, bone marrow). ML may arise from sites other than the lymph nodes. These are grouped together as extranodal lymphomas and have different staging.



TABLE 10-1


CLASSIFICATION OF ANEMIAS*

















































Category RBCs Characteristics
Blood loss, acute Initially: normochromic, normocytic
Later: hypochromic reticulocytosis
Acute volume depletion
RBC reduction secondary to fluid influx
Rapid RBC regeneration
Blood loss, chronic Hypochromic Reduced iron stores
Increased Destruction of Erythrocytes
Hemolytic anemias   Features of hemolysis and tissue siderosis
Bone marrow: significant erythropoietic hyperplasia
Splenomegaly
Immunologic Reticulocytosis Autoantibodies against RBC (infection or drug induced)
Isohemagglutinins (transfusion induced, erythroblastosis fetalis)
Mechanical Schistocytes Microangiopathic:
 Hemolytic uremic syndrome
 Thrombotic thrombocytopenic purpura
 Trauma by intracardiac artificial devices
 Multiple hemangiomas (e.g., hepatic)
Hereditary Spherocytosis
Elliptocytosis
Sickle cells
Hypochromic, microcytic
Heinz bodies
RBC membrane and cytoskeleton deficiencies
Hemoglobinopathies: sickle cell anemia, thalassemia
Enzyme deficiencies (e.g., of hexose monophosphate shunt)
Deficient Erythropoiesis
“Stem cell” defect Normochromic,
Normocytic to mildly macrocytic
Aplastic anemia (with pancytopenia), pure red cell aplasia secondary to myelofibrosis (with thrombocytopenia, splenomegaly)
Maturation defect Megaloblastic
Anisocytic
Hypochromic
Poikilocytic
Pernicious anemia (vitamin B12 deficiency), folate deficiency, anemia, iron deficiency (infection, tumor, chronic blood loss)
Hb synthesis defect Sideroblasts Sideroblastic anemia


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normochromic: normal color (i.e. normal Hb content); normocytic: normal size and shape of RBC; hemolytic: red cell lysis


*Hb indicates hemoglobin; RBC, red blood




TABLE 10-3


CLASSIFICATION IN SUBTYPES OF ACUTE MYELOPROLIFERATIVE DISEASES*


















































FAB Class Subtype Name Abbreviation Proportion of Acute Myeloproliferative Diseases (%)
M0 Acute myeloblastic leukemia, stem cell (i.e., minimal differentiation) AML 3-5
M1 Acute myeloblastic leukemia without maturation AML 15-20
M2 Acute myeloblastic leukemia with maturation AML 25-30
M3 Acute promyelocytic leukemia APL 5-20
M4 Acute myelomonocytic leukemia AMML 20-30
M5 Acute monoblastic leukemia AMOL 2-9
M6 Acute erythroleukemia AEL 3-5
M7 Acute megakaryoblastic leukemia   3-12


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FAB indicates French-American-British classification.


*Acute myeloproliferative diseases are clonal neoplastic disorders of hematopoietic stem cells, the classification of which is determined by their preferential cytologic differentiation.


Adapted from Hoffman R et al. Hematology. Philadelphia: Churchill-Livingstone; 2000.



TABLE 10-4


CLASSIFICATION OF LYMPHOMA (NHL) ENTITIES
Revised European American Lymphoma (REAL) Classification



















B-Cell Lymphomas T-Cell and NK-Cell Lymphomas
Precursor B-Cell Neoplasias Precursor T-Cell Neoplasia


Peripheral B-Cell Neoplasias Pewripheral T-Cell and NK-Cell Lymphomas


1. B-cell chronic lymphatic leukemia (B-CLL) or prolymphocytic leukemia (B-PLL)


2. Small cell lymphocytic lymphoma


3. Lymphoplasmacytoid lymphoma (LPL) or immunocytoma (IC)


4. Mantle cell lymphoma


5. Follicular center cell lymphoma, follicular pattern (FCCf)



6. Follicular center cell lymphoma, small cell, diffuse pattern (FCCd)


7. Marginal zone lymphoma (MZL)



8. Margonal zone lymphoma of the spleen (SLVL)


9. Hairy cell leukemia (HCL)


10. Plasmacytoma/multiple myeloma


11. Diffuse large cell B-cell lymphoma subtype: primary B-cell lymphoma of mediastinum (of thymic origine)


12. Burkitt lymphoma


13. B-cell lymphoma of high malignancy of Burkitt type




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Figure 10-1 Acquired Anemias
Classification of anemias by immediate cause is shown in Table 10-1. Acute blood loss initially causes blood volume depletion; normochromic anemia becomes overt 24 to 48 hours later, after some volume is replaced. Chronic blood loss (e.g., in intestinal ulcers, polyposis, hypermenorrhea) with depletion of the body’s iron stores causes hypochromic anemia. Erythrocyte destruction causes several anemias. Immunohemolytic anemia arises spontaneously after infection or drug treatment or in erythroblastosis fetalis, the incompatibility of erythrocyte antigens between an Rh-negative mother and her Rh-positive fetus. Microangiopathic hemolytic anemia (MAHA) is caused by mechanical shear forces from fibrin strands in small vessels (hemolytic uremic syndrome, disseminated intravascular coagulation, or multiple hemangiomas) or from artificial devices in the bloodstream (e.g., cardiac valvular prostheses). Peripheral blood smears show fragmented erythrocytes (schistocytes, fragmentocytes).

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Jun 28, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Hematopoietic and Lymphatic Tissues
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