White Blood Cell Pathology

NHL Subdivision Based on Cell Size

(focus on B-cells bc accounts for vast majority) *Small B-cells* are highly differentiated; look very similar to normal B-cells; can result in: -follicular lymphoma -mantle cell lymphoma -marginal zone lymphoma -small lymphocytic lymphoma (CLL cells involve tissue) *Intermediate B-cells* -resulting in Burkitt Lymphoma *Large B-cells* -resulting in diffuse large B-cell lymphoma

Chronic Lymphocytic Leukemia

CLL is a neoplastic proliferation of naive B-cells that *co-express CD5 and CD20* (CD5 is normally expressed by T-cells but aberrant expression by B-cells) -most common leukemia overall marked by increased lymphocytes and *smudge cells* involvement of lymph nodes leads to generalized lymphadenopathy and is called *small lymphoblastic lymphoma* complications of *hypogammaglobulinemia* in which infection is most common cause of death; bc neoplastic B-cells are NOT producing immunoglobulins *autoimmune hemolytic anemia* if neoplastic B-cells do attempt Ig synthesis they are autoimmune transformation to *diffuse large B-cell lymphoma* due to Richter Transformation (additional mutations) gives rise to more aggressive tumor (enlarging lymph node/spleen)

Essential Thrombocythemia

neoplastic proliferation of mature myeloid cells *especially platelets* associated with a *JAK 2 kinase mutation* clinical symptoms are due to *increase risk for bleeding and/or thrombosis* -must differentiate from iron-deficiency anemia differs from other myeloproliferative disorders bc it RARELY progresses to marrow fibrosis or acute leukemia also NO significant risk for hyperuricemia or gout (platelets lack nuclei so degradation does not increase uric acid)

Letterer-Siwe Disease

*malignant* proliferation of Langerhans cells classic presentation is *skin rash* and cystic skeletal defects presents typically in *infant < 2* multiple organs may be involved and can be rapidly fatal

Hand-Schuller-Christian Disease

*malignant* proliferation of Langerhans cells classic presentation is scalp rash, lytic skull defects, diabetes insipidus, and exopthalmos presents in a child (over age 3)

Polycythemia vs Reactive Polycythemia

*reactive polycythemia* is a secondary result of some other problem: ie Cardiovascular or Pulmonary disorders resulting in low O2 delivery to tissues (body compensates by producing more hemoglobin, ie more RBCs) 1. in PV the *EPO levels decrease* due to negative feedback of RBC overload, and *SaO2 is normal* 2. if reactive polycythemia is due to inadequate oxygenation the SaO2 is LOW and therefore EPO increased 3. if reactive polycythemia is due to ectopic EPO production (renal cell carcinoma) EPO is high while SaO2 is normal

Myelodysplastic Syndrome

pre-existing dysplasia which can give rise to *AML* especially associated with prior exposure to *alkylating agents or radiotherapy* usually clinically presents with *cytopenias*, hypercellular bone marrow, abnormal maturation of cells, and increased blasts (< 20%) most pts die from infection or bleeding, through some *progression to acute leukemia* (marked by increase to > 20% blasts)

Lymphopenia

specific type of *leukopenia* caused by decrease number of circulating *lymphocytes* causes include: *1. Immunodeficiency* such as HIV or DiGeorge Syndrome (lack of 3/4 pharyngeal pouches means no Thymus for T-cell maturation) *2. High Cortisol* either from exogenous corticosteroids or Cushing Syndrome; cortisol induces apoptosis of lymphocytes *3. Autoimmune Destruction* especially SLE produces antibodies towards blood cells *4. Whole Body Radiation* lymphocytes are the MOST sensitive cells to radiation; lymphopenia is earliest change to emerge after radiation

WBC Counts

via hematopoiesis, cells mature and are released from the bone marrow into the blood stream *normal* WBC count is around 5-10 K/microL *leukopenia* is a LOW WBC count < 5K *leukocytosis* is a HIGH WBC count > 10K a low or high WBC count is usually due to a decrease or increase in one particular cell lineage

Neutropenia

a specific type of *leukopenia* due to a decreased number of circulating *neutrophils* causes include *1. drug toxicity* such as chemotherapy with alkylating agents (targets rapidly dividing cells) and damage to stem cells results in decrease production of WBC's, especially neutrophils, and *2. severe infection* increases movement of neutrophils into tissues, decreasing amount in circulation (serum) *GM-CSF or G-CSF* used as treatment to boost granulocyte production (decrease risk of infection)

Acute Megakaryoblastic Leukemia

high yield subtype of AML based on lineage of immature myeloid cells proliferation of *megakaryoblasts* which lack MPO associated with *Down Syndrome* which usually arises BEFORE age 5 (different from leukemia arising after age 5 in down syndrome is usually ALL)

Acute Monocytic Leukemia

high yield subtype of AML based on lineage of immature myeloid cells proliferation of *monoblasts* usually lack MPO staining blasts characteristically infiltrate gums causing *gum swelling*

Infectious Mononucleosis Complications

increase risk for *splenic rupture* bc splenomegaly causes stretching of capsule -pts advised to avoid contact sports for 1 month *rash* if exposed to ampicillin *dormancy* of virus in B-cells leads to increased risk for both recurrence and B-cell lymphoma (EBV associated with lymphomas), especially if immunodeficiency develops

Neutrophilic Leukocytosis

increased circulating neutrophils caused by: *1. bacterial infections or necrotic tissue* are the 2 driving forces of inflammation: induces release of marginated pool and bone marrow neutrophils, including immature forms (left shift) characterized by *decrease CD16 (Fc receptor)* expression (have lower functioning) *2. high cortisol state* impairs leukocyte adhesion; leading to release of marginated pools of neutrophils (population that hangs out in vessels; fall out into blood stream)

Acute Myeloid Leukemia

neoplastic accumulation of *immature myeloid cells* > 20% in the bone marrow myeloblasts characterized by *positive cytoplasmic staining for myeloperoxidase (MPO)* -crystal aggregates of MPRO may be seen as *Auer Rods* most commonly arises in older adults (avg 50-60) subclassification is based on cytogenetic abnormalities, lineage of immature myeloid cells, and surface markers

Chronic Myeloid Leukemia

neoplastic proliferation of myeloid cells, *especially granulocytes* and their precursors and characteristically increased *basophils* driven by the Philadelphia Chromosome, *t(9;22)* which generates a *BCR-ABL* fusion protein with *increased tyrosine kinase activity* resulting in cell overgrowth -first line treatment is *imatinib* which blocks tyrosine kinase activity 1. Chronic Phase: marked by *splenomegaly* is common 2. Accelerated Phase: marked by actively enlarging spleen is often shortly followed by malignant transformation: 3. Transformation Phase: *acute leukemia* -2/3 of cases result in AML -1/3 of cases result in ALL

Nodular Sclerosis

*most common* subtype of HL (70% of all cases) classic presentation is an enlarging cervical or mediastinal lymph node in a young adult, usually female lymph node is divided by *bands of sclerosis* RS cells are present in lake-like cells termed *lacunar cells*

Follicular Lymphoma vs Reactive Follicular Hyperplasia

*reactive follicular hyperplasia* is a potential normal response to infection that is NOT neoplastic 1. lymphoma results in *disruption of normal lymph node architecture* marked by follicles extending beyond cortex 2. lack of *tingible body macrophages* in germinal centers in lymphoma (creates white space marking apoptosis normally present in reactive hyperplasia) 3. *Bcl2 positive* expression in lymphoma 4. lymphoma is *monoclonal* vs reactive hyperplasia is polyclonal (alpha/kappa chain ratio of 3:1)

Lymphocytic Leukocytosis

refers to increased circulating lymphocytes, caused by: *1. Viral Infections* associated with CD8+ T-cells; causes T-lymphocytes to undergo hyperplasia in response to virally infected cells (presentation of MHC-I) *2. Bordetella pertussis Infection* (the one bacterial exception) bc microbe produces lymphocytosis-promoting factor which BLOCKS circulating lymphocytes from leaving blood to enter the lymph node

Basic Principles of Chronic Leukemia

refers to neoplastic proliferation of *mature circulating lymphocytes* characterized by a high WBC count usually insidious in onset; pt typically asymptomatic often presents in older adults

Multiple Myeloma

*malignant proliferation of plasma cells* in the bone marrow this is the most common primary malignancy of bone BUT metastatic cancer of bone is most common malignant lesion of bone overall *high serum IL-6* often present; stimulates plasma cell growth and immunoglobulin production clinical symptoms are dependent on the products of the plasma cells

Clinical Presentation of Multiple Myeloma

*1. Bone Pain with Hypercalcemia* with production of osetoclast activating factor, activating *RANK receptor* on osteoclasts leading to bone destruction -lytic punched out skeletal lesions on xray, especially on vertebrae and skull (increase risk for fracture) *2. Elevated Serum Protein* with production of immunoglobulin creates *M-spike* on serum protein electrophoresis (SPEP) often *monoclonal IgG or IgA* *3. Increase Risk for Infection* bc monoclonal Ab lacks antigenic diversity; infection is mc cause of death *4. Rouleaux Formation* of RBC's (stacking up) due to decrease charge between cells as result of increase protein *5. Primary AL Amyloidosis* as free light chains circulate in serum and deposit in tissues *6. Proteinuria* as free light chains are excreted in urine as *Bence Jones Protein* or deposited in kidney tubules increasing risk for kidney failure *(myeloma kidney)*

ALL Subtypes

*B-ALL* is the most common type -characterized by lymphoblasts that express *CD10, CD19, CD20* -excellent response to chemotherapy (but cant pass thru testes and blood brain barrier; scrotum and CSF prophylaxis required) -prognosis is based on cytogenetic abnormalities *t(12;21)* has a GOOD prognosis; more common in children *t(9;22)* has POOR prognosis; more commonly seen in adults (Philadelphia + ALL) *T-ALL* -characterized by lymphoblasts that express markers ranging from *CD2-CD8* (but NEVER CD10) -usually present in teenagers as mediastinal (thymic) mass; therefore referred to as *acute lymphoblastic lymphoma*

Waldenstrom Macroglobulinemia

*B-cell lymphoma with monoclonal IgM production* results in generalyed LAD absence of lytic bones lesions (NOT MM) increase serum protein *M spike of monoclonal IgM* (differs from MM has monoclonal IgG) clinical presentations are result of *hyperviscosity of serum* bc increase IgM (large pentamer) -visual and neurologic deficits (ie retinal hemorrhage or stroke) -bleeding bc viscous serum results in defective platelet aggregation acute complications treated with *plasmapheresis* to remove IgM from pt serum

Basic Principles of Langerhans Cell Histiocytosis

*Langerhans Cells* are specialized dendritic cells found predominantly in the skin -derived from bone marrow monocytes -present antigens to naive T-cells langerhans cell histiocytosis is a *neoplastic proliferation* results in characteristic *Birbeck granules* (look like tennis rackets) on electron microscopy cells are *CD1a+ and S100+* on immunohistochemistry

Other Leukocytosis Types

*Monocytosis* -increased circulating monocytes -due to chronic inflammatory states (autoimmune and infectious) and malignancy *Eosinophilia* -increased circulating eosinophils -causes include allergic reactions (Type I HSR), parasitic infections, and Hodgkin Lymphoma (increase IL-5 is the eosinophil chemotactic factor) *Basophilia* -increased circulating basophils -classically seen in Chronic Myeloid Leukemia (CML)

Infectious Mononucleosis Diagnosis

*Monospot Test* is used for screening: -detects *IgM* antibodies that cross-react with horse or sheep red blood cells (heterophile antibodies; have affinity to bind RBCs of another animal) -usually turns positive within 1 week after infection -negative test may suggest CMV as possible cause *Serologic Testing* for EBV viral capsid antigen must be used as confirmatory test for definitive diagnosis

Eosinophilic Granuloma

*benign* proliferation of Langerhans cells in bone classic presentation is *pathologic fracture* in an adolescent; skin often NOT involved biopsy shows Langerhan cells with mixed inflammatory cells including numerous *eosinophils* (note that osteosarcoma is NOT the only cause of pathologic fractures in adolescents)

Lymphadenopathy

*enlarged lymph nodes* can either result in: 1. *Painful LAD* usually seen in lymph nodes that are draining a region of *acute infection* (acute lymphadenitis) 2. *Painless LAD* usually seen in *chronic inflammation*, metastatic carcinoma, or lymphoma during inflammation the lymph node enlargement is due to *hyperplasia of particular regions* of the lymph node: 1. *Follicular Hyperplasia* involves the B-cell region -seen in RA and early stages of HIV infection -follicles extend beyond the layer of the cortex 2. *Paracortex Hyperplasia* involves the T-cell region -seen in viral infections (infectious mononucleosis) 3. *Hyperplasia of Sinus Histiocytes* involve medulla -usually seen in nodes draining a tissue with cancer

Monoclonal Gammopathy of Undetermined Significance (MGUS)

*increase serum protein with M spike on SPES* BUT all other features of multiple myeloma are absent (no lytic bone lesions, no hypercalcemia, no AL amyloidosis, no Bence Jones proteinuria, etc) common in elderly 1% of these pts go on to develop multiple myeloma each year (possible pre-myeloma/dysplasia like state)

CML vs Leukemoid Reaction

*leukemoid reaction* is the natural reaction of infection, also termed reactive neutrophilic leukocytosis 1. CML is negative for *leukocyte alkaline phosphatase* LAP stain (enzyme present in granulocytes fighting infection) 2. CML has characteristic increased *basophils* vs infection produces left shift (increase neutrophils) 3. the *t(9;22)* is absent in leukemoid reaction

Infectious Mononucleosis

*lymphocytic leukocytosis caused by EBV infection* -leukocytosis comprised of reactive CD8+ T-cells -CMV is a less common cause -EBV transmitted by saliva (kissing disease) infection is primarily of oropharynx causing pharyngitis liver involvement results in hepatitis with hepatomegaly and elevated liver enzymes virus can also infect B-cells *CD8+ T-cell Response Manifested As...* 1. generalized lymphadenopathy due to T-cell hyperplasia in the LYMPH NODE PARACORTEX 2. splenomegaly due to T-cell hyperplasia in the PERIARTERIAL LYMPHATIC SHEATH (PALS) 3. high WBC count with ATYPICAL lymphocytes (reactive CD8+ Tcells) look like monocytes with with large nucleus and abundant blue cytoplasm

Acute Lymphoblastic Leukemia

ALL is a neoplastic accumulation of *lymphoblasts* > 20% in the bone marrow lymphoblasts characterized by *positive nuclear staining for Tdt* a DNA polymerase which is absent in myeloid blasts (differentiates AML) and mature lymphocytes most commonly arises in *children* and associated with Down Syndrome, usually arising AFTER age 5 ALL can be further classified into B-ALL and T-ALL based on cell surface markers

Acute Promyelocytic Leukemia

APL is a high yield subtype of AML based on cytogenetic abnormalities characterized by *t(15;17)* involving translocation of retinoic acid receptor, *RAR* on chromosome 17 to chromosome 15 -RAR disruption blocks maturation, causing promyelocytes (blasts) to accumulate -abnormal promyelocytes contain numerous primary granules that increase risk for *DIC* (auer rods can activate the coagulation cascade) -must be treated with *all trans retinoic acid* (ATRA is a vitamin A derivative) which binds altered receptor, causing blasts to mature and die

Adult T-cell Leukemia/Lymphoma

ATLL is a neoplastic proliferation of *mature CD4+ T-cells* associated with *HTLV-1* (human T-lymphotropic virus) most commonly seen in Japan and Caribbean clinically presents with *rash* (bc CD4+ Tcells have strong predilection for skin infiltration), generalized lymphadenopathy and hepatosplenomegaly, and *lytic (punched out) bone lesions with hypercalcemia* (present with rash important to differentiate from multiple myeloma!!!)

Basic Principles of Acute Leukemia

characterized by a neoplastic proliferation of Blasts (immature cells) accumulating as *>20% blasts in bone marrow* due to loss of ability to mature cells increased blasts *"crowd out" normal hematopoeisis* resulting in ACUTE presentation of anemia (fatigue), thrombocytopenia (bleeding), or neutropenia (infection) blasts usually enter blood streaming resulting in *high WBC count* blasts appear on smear as *large immature cells with punched out nucleoli* acute leukemia is subdivided based on phenotypes of blasts into: acute lymphoblastic leukemia *(ALL)* and acute myelogenous leukemia *(AML)*

WBC Basic Principles

hematopoiesis occurs via stepwise maturation of *CD34+ hematopoietic stem cells* give rise to: *A. Myeloid Stem Cells* (myeloidblasts) 1. Erythroblasts > RBCs 2. Myeloblasts > Granulocytes (Neutrophils, Basophils, Eosinophils) 3. Monoblasts > Monocytes 4. Megakaryoblasts > Megakaryocytes *B. Lymphoid Stem Cells* (lymphoblasts) 1. B-Lymphoblasts > B-cells/Plasma Cells 2. T-Lymphoblasts > T-cells (CD4+/CD8+)

Hodgkin Lymphoma

neoplastic proliferation of *Reed-Sternberg (RS) Cells* which are large B-cells with multilobed nuclei and prominent nucleoli (owl-eyed nuclei) which are classically *positive for CD15 and CD30* differs from NHL which has entire mass composed of tumor cells; HL has mass composed predominantly of inflammatory cells with small amount neoplastic cells *RS cells secrete cytokines* -attracts reactive lymphocytes, plasma cells, macrophages, and eosinophils (contribute to mass) -may lead to fibrosis -occassionally results in "B-symptoms" (fever, chills, weight loss, night sweats) subtypes based on reactive inflammatory cells: 1. Nodular Sclerosis (most common) 2. Lymphocyte-rich: best prognosis 3. Mixed Cellularity: abundant eosinophils due to IL-5 4. Lymphocyte-depleted: most aggressive, often seen in elderly and HIV positive pts

Burkitt Lymphoma

neoplastic proliferation of *intermediate sized B-cells (CD20+)* associated with *EBV infection* classically presents as an extranodal mass in children or young adults; exists in 2 classic forms: *African form* usually involves the jaw *Sporadic form* usually involves the abdomen driven by various translocations of c-myc, most common being *t(8;14)* resulting in tanslocation of c-myc from chromosome 8 to Ig heavy chain locus of chromosome 14 resulting in *overexpression of c-myc oncogene promoting cell growth* characterized by HIGH mitotic index and *'starry sky'* appearance (blue sky with white tangible macrophages forming stars)

Diffuse Large B-Cell Lymphoma

neoplastic proliferation of *large B-cells (CD20+)* that grow diffusely in sheets this is the most common form of NHL *highly aggressive, poor prognosis* (large B-cells are the least differentiated, abnormal structure, most malignant) arises sporadically or from transformation of a low-grade lymphoma (such as follicular lymphoma) presents in late adulthood as an enlarging lymph node or extranodal mass

Basic Principles of Lymphoma

neoplastic proliferation of *lymphoid cells that forms a mass* which can arise in lymph nodes or extranodal tissue classified as either *Non-Hodgkin Lymphoma* (60%) and *Hodgkin Lymphoma* (40%) Non-Hodgkin Lymphoma (NHL) is further subdivided based on cell size, pattern of growth, expression of surface markers, and cytogenetic translocations

Hairy Cell Leukemia

neoplastic proliferation of *mature B-cells* characterized by *hairy cytoplasmic processes* cells are positive for tartrate-resistant acid phosphatase *(TRAP)* clinical features include: *splenomegaly* due to accumulation of hairy cells within the RED PULP of spleen), *"dry tap" on bone marrow aspiration* due to marrow fibrosis, and lymphodenoapthy is ABSENT (cells TRAP in red pulp, wont be found in usual location of lymph nodes) has excellent response to *2-CDA (cladribine)* an adenosine deaminase inhibitor: adenosine accumulates to toxic levels in neoplastic B-cells (causing death)

Mycosis Fungoides

neoplastic proliferation of *mature CD4+ T-cells* that infiltrate the skin, producing localized skin rash, plaques, and nodules aggregates of neoplastic cells in the epidermis are called *Pautrier microabscesses* cells can spread to involve the blood, producing *Sezary syndrome* characterized by lymphocytes with *cerebriform nuclei* on blood smear (highly lobular appearance to nuclei, dark staining cell)

Basic Principles of Myeloproliferative Diseases

neoplastic proliferation of *mature cells of myeloid lineage* disease of late adulthood (avg age 50-60) cells of ALL myeloid lineages will be increased, but classified based on the DOMINANT cell produced -results in high total WBC count and hypercellular bone marrow complications include *increase risk for hyperuricemia and gout* due to high turnover of cells (nucleus degradation increases uric acid) as well as progression to marrow fibrosis or *transformation to acute leukemia*

Follicular Lymphoma

neoplastic proliferation of *small B-cells (CD20+)* that result in *follicle-like nodules* often presents in late adulthood as painless LAD driven by *t(14;18)* involving BCL2 on chromsome 18 translocating to Ig heavy chain locus on chromosome 14 results in *overexpression of BCL2 inhibiting apoptosis* (apoptosis desired in lymph nodes to get rid of excess cells from somatic hypermutation) treatment reserved for symptomatic pts; involves chemotherapy or *rituximab (anti-CD20 Ab)* potential progression to *diffuse large B-cell lymphoma* presents as a singly enlarging lymph node

Mantle Cell Lymphoma

neoplastic proliferation of *small B-cells (CD20+)* that results in expansion of *mantle zone* (region immediately adjacent to follicles) presents in late adulthood with painless LAD driven by *t(11;14)* involving *Cyclin D1* gene on chromsome 11 translocation to Ig heavy chain locus on chromosome 14 resulting in *overexpression of cyclin D1* which promotes cell cycle transition from *G1 to S phase* -facilitating neoplastic proliferation

Marginal Zone Lymphoma

neoplastic proliferation of *small B-cells (CD20+)* that results in expansion of *marginal zone* (region outside of mantle; most lymph nodes don't normally have a marginal zone; induced only during inflammation) associated with *chronic inflammation* such as Hashimoto thyroiditis, Sjogren Syndrome, and H pyloris gastritis -marginal zones formed by post-germinal center B-cells *MALToma* is a marginal zone lymphoma in mucosal sites; ie Gastric MALToma may regress with clearance of H pylori

Myelofibrosis

neoplastic proliferation of mature myeloid cells *especially megakaryocytes* 50% of cases associated with*JAK 2 kinase mutation* megakaryocytes produce *increase platelet derived growth factor (PDGF)* causing marrow fibrosis (increase stroma) *splenomegaly* results from extramedullary hematopoiesis (fibrosed marrow cant produce cells efficiently so spleen takes over) *leukoerythroblastic smear* has characteristic tear-drop RBCs (from squeezing out of marrow), nucleated RBCs and immature granulocytes due to lack of reticulin in spleen to regulate release of mature cells *increase risk of infection, thrombosis, and bleeding*

Polycythemia Vera

neoplastic proliferation of mature myeloid cells, *especially RBCs* associated with a *KAJ 2 kinase mutation* clinical presentation due to *hyperviscosity of blood* (loaded with RBCs creates super thick blood) -blurry vision and headache -increase risk of venous thrombosis; ie *Budd Chiari Syndrome* involving hepatic vein -flushed face due to congestion (plethora) -itching, especially after bathing (due to histamine release from increased mast cells) treatment with *phlebotomy* to reduce blood cells or second line therapy of *hydroxyurea* -high mortality (within 1 year) if untreated