Hematopathology: Overview


I.                     Other

a.        Reactive Lymphadenitis

                                                               i.      toxoplasmosis

                                                             ii.      infectious mononucleosis

                                                           iii.      cat scratch disease

b.        Myelodysplastic Syndrome (MDS)

                                                               i.      Low Grade MDS

                                                             ii.      High Grade MDS

c.        Chronic Myeloproliferative Disorders

                                                               i.      Chronic Myelogenous Leukemia (CML: also see Leukemia)

                                                             ii.      Polycythemia Vera

                                                           iii.      Essential thrombocythemia

                                                            iv.      Chronic Idiopathic Myelofibrosis

d.        Leukemoid reaction

II.                   Leukemia

a.        Acute Leukemia

                                                               i.      Acute Myelogenous Leukemia (AML)

1.        myelodysplasia-related (MDR-AML)

2.        de novo (DN-AML)

-          acute promyelocytic leukemia (APL)

                                                             ii.      Acute Lymphoblastic Leukemia (ALL)

1.        Precursor B-Cell ALL

2.        Precursor T-Cell ALL

b.        Chronic Leukemia

                                                               i.      Chronic Myelogenous Leukemia (CML)

                                                             ii.      Chronic Lymphocytic Leukemia (CLL) / Small Lymphocytic Lymphoma (SLL)

                                                           iii.      Hairy Cell Leukemia

III.                 Lymphoma

a.        Non-Hodgkin’s Lymphoma

                                                               i.      B-Cell Lymphomas

1.        Burkitt’s Lymphoma

2.        Follicular Cell Center Lymphoma (FCCL)

3.        Diffuse Large B cell Lymphomas

4.        Multiple Myeloma

5.        Extranodal marginal zone lymphoma of mucosal associated tissue (MALT lymphoma)

                                                             ii.      T-Cell Lymphomas

1.        T-lymphoblastic lymphoma/leukemia

2.        Mycosis Fungoides (MF) and Sézary Syndrome

3.        Peripheral T-cell lymphoma, unspecified

4.        Anaplastic Large Cell (Ki-1+) Lymphoma (ALCL)

b.        Hodgkin’s Lymphoma

                                                               i.      Classical HL

1.        Nodular Sclerosing Hodgkin’s Lymphoma (NSHL)

2.        Mixed Cellularity Hodgkin’s Lymphoma (MCHL)

3.        Lymphocyte Rich Classical Hodgkin Lymphoma (LRCHL)

4.        Lymphocyte Depleted Hodgkin's Lymphoma (LDHL)

                                                             ii.      Non-Classical HL

1.        NLPHD



         I.      Other

a.        Reactive Lymphadenitis

                                                         i.      toxoplasmosis

                                                       ii.      infectious mononucleosis

                                                     iii.      cat scratch disease

focal abscesses

b.        Myelodysplastic Syndrome (MDS) = preleukemic syndrome


A group of clonal stem cell disorders.

Maturation defects à ineffective hematopoiesis

Age > 50

Peripheral cytopenias, Hypercellular marrow

Dysplastic morphology

- Erythroid: multinucleated cells, dyssynchronous maturation of nucleus and cytoplasm

- Granulocytes: bilobed nuclei (Pelger-Huet cells), abnormal/absent granules

- Platelets: may lack granules, may be abnormally large

May have history of exposure to chemotherapy or radiation

10-40% à develop MDR-AML

Treatment: supportive – blood transfusions, antibiotics (transplantation is only cure)

abnormalities: CD8+,CD7-,CD5-

                                                         i.      Low Grade MDS

Normal blast count, refractory anemia, 6-year avg. survival

                                                       ii.      High Grade MDS

Excess blasts, refractory anemia, 6-8 month avg. survival

Often have history of chemotherapy or radiation

c.        Chronic Myeloproliferative Disorders

Neoplastic stem cell proliferation with differentiation

                                                         i.      Chronic Myelogenous Leukemia

See leukemia below

                                                       ii.      Polycythemia Vera

increased RBC production (not secondary to elevated erythropoietin)

hyperviscosity of blood à thrombotic episodes

suspicious: mesenteric, portal, splenic vein thrombosis

increased GI bleeding

Two phases

1.        polycythemic phase

2.        spent phase

                                                     iii.      Essential thrombocythemia

megakaryocytic lineage with sustained thrombocytosis (platelet production > 600,000)

first exclude: infection, neoplasm, splenectomy, iron deficiency

thrombosis: splenic, hepatic vein

minimal fibrosis

                                                      iv.      Chronic Idiopathic Myelofibrosis

dysplasia/proliferation: megakaryocytic and granulocytic cells in bone marrow

Reticulin fibrosis in marrow (osteosclerosis) à spleen hematopoiesis (splenomegaly)

Findings: nucleated RBC’s

median survival: 3-5 years

à acute leukemia (5-30%)

megakaryocytic lineage

d.        Leukemoid reaction

bands, lymphocytes, neutrophils in blood (marrow is not packed or malignant)

resembles leukemia peripherally (but no bone marrow involvement)

etiology: infectious disease, intoxication, neoplasms, acute hemorrhage

may be lymphocytic, monocytic, myelocytic, plasmocytic

       II.      Leukemia

Marrow-based, clonal, malignant, Hematopoietic.

            Diagnosed by finding blasts in peripheral blood and bone marrow (hypercellular).

a.        Acute Leukemia

Blasts predominate

- Lose ability to differentiate

- High N:C ratio, fine chromatin, distinct nuclei

- Myeloblasts cannot be morphologically distinguished from lymphoblasts

                - Auer rods (rare) represent myeloblasts

Signs/Symptoms: marrow failure, cytopenias, organ infiltration (spleen, lymph nodes, liver, CSF, testis, etc.), leukostasis

                                                         i.      Acute Myelogenous Leukemia (AML)

Sudan Black+ (lipid granules: granulocytes), Esterase+ (monocytes), MPO+

CD13, CD33, CD117

85% of adult acute leukemia

Features: hypercellular marrow, monomorphic blasts (most common: myeloblastic)

Old classification: FAB classification

1.        Myelodysplasia-Related (MDR-AML)

median age: 62, poor prognosis, not candidates for transplant

poorly responsive to cytotoxic chemotherapy

2.        de novo (DN-AML) = AML with recurrent cytogenic abnormalities

younger: median age 30’s


organ involvement less frequent than MDR-AML

responds well to chemotherapy

young: therefore transplant candidate

two steps required for de novo AML

1) differentiation mutation

2) proliferation mutation

e.g. Flt3: drives proliferation of myeloid stem cells (15-25% of de novo AML)

a.        Acute Promyelocytic Leukemia (APL)

10% of AML (auer rods more common in)

60-70% survival with ATRA therapy

blasts resemble promyelocytes

* t(15;17) )(PML/RARa)

- RARa = retinoic acid receptor (steroid hormone family)

- mediates myeloid differentiation

- RA activates normal RARa by releasing a co-repressor complex containing histone deacetylase

- mutant PML-RARa is not activated by physiological levels of RA

- mutant PML-RARa is activated by pharmacologic levels of ATRA (all-trans RA)

                à differentiation of Promyelocytic blasts (remission)

                                                                            * variant translocation: t(11:17)(PLZF-RARa) is resistant to pharmacologic doses)

                                                       ii.      Acute Lymphoblastic Leukemia (ALL) / Lymphoblastic Lymphoma

TdT, CD2,CD3

Surface immunoglobulin negative

most common childhood malignancy

85% of acute leukemia in children (good prognosis: chemo. successful 70% of children)

15% of adult acute leukemia (poorer prognosis)

Signs/Symptoms: splenomegaly, hepatomegaly, lymphadenopathy (leukemic infiltrates), hypercellular marrow

1-2%: Burkitt’s Lymphoma’s leukemic counterpart (CD19, CD10, CD20, surface Ig)

1.        Precursor B-Cell ALL (85%)

TdT, CD19

good risk: t(12;21)

poor risk: t(9;22)

2.        Precursor T-Cell ALL (15%)

TdT, CD2, CD3, CD7

classic presentation: mediastinal mass in adolescent male (thymus)

average prognosis

b.        Chronic Leukemia

Differentiated cells predominate.  Insidious, with long relatively long survival (years).

Possibility of transformation to acute leukemia exists

                                                         i.      Chronic Myelogenous Leukemia (CML)

age 25-60

15-20% of leukemias

most common myeloproliferative disease

splenomegaly (sense of “fullness”)

megakaryocytes throughout

t(9;22)(ABL-BCR) Philadelphia chromosome

Drug that targets: STI571, Gleevec

Distinguish from leukemoid by: WBC>50,000, absence of toxic neutrophils, blasts, increased platelets, splenomegaly, no fever, karyotype(9;22), abnormal megakaryocytes

Three Phases

1.        chronic

a.        hypercellular marrow (blasts < 10%)

b.        immature myeloids in plasma (but blasts < 2%)

c.        basophilia

2.        accelerated

a.        increased basophilia

b.        blood/marrow blasts: 10-20%

3.        blast crisis

a.        blasts > 20%

b.        70% myeloid blast crisis (AML)

c.        30% lymphoid blast crisis (ALL)

                                                       ii.      Chronic Lymphocytic Leukemia (CLL) / Small Lymphocytic Lymphoma (SLL)

B lymphocyte leukemia

size: small/round

Most common adult leukemia in Western world

Median age: 65 (most indolent type of leukemia – more likely to die of other causes - incurable)

Signs/Symptoms: asymptomatic, anemia, infections, hepatosplenomegaly, lymphadenopathy, lymphocytosis, hypogammaglobulinemia

Pathology: Almost always B-Cells (CD20, CD5, CD23)

1. blood: small lymphocytes

2. bone marrow: small lymphocytes

3. lymph nodes: small lymphoctes


1. Richter’s syndrome (transformation to large cell lymphoma) 10%

2. Prolymphocytic transformation 13-30%


                                                1. Hypogammaglobulinemia à bacterial infection

                                                2. Hypoproliferative or Autoimmune hemolytic anemia/thrombocytopenia


                                                1. Mutation status of immunoglobulin V genes is important for prognosis (mutated: better prognosis)

                                                2. trisomy 12, del 13q14, del 11q22-23

                                                     iii.      Hairy Cell Leukemia

B lymphocyte leukemia (CD20) with distinctive morphology (rare: 2%)

median age: 55

male:female = 5:1

Clinical presentation: 1) splenomegaly; 2) pancytopenia; 3) recurrent infections

Hairy cells on peripheral blood smear

CD20, CD103, CD11c, CD25

Indolent, sensitive to nucleotide analog therapy (2-CDA)

     III.      Lymphoma

a.        Non-Hodgkin’s Lymphoma

85% of lymphomas


unpredictable spread

Neoplastic cells predominant

<50% cure overall

large/medium cells: aggressive

small cells: indolent

                                                         i.      B-Cell Lymphomas

most common immune malignancy

more common in immunocompromised patients


VDJ recombination-induced

1.        SLL

equivalent to CLL (see above)

2.        Burkitt’s Lymphoma

African subtype: jaw mass (EBV+malaria)

Sporadic: GI tract involvement (EBV)

morphology: diffuse, blast-like

Many (non-malignant) macrophages eat the dead tumor cells (diffuse “starry sky”)

size: medium (aggressive)

Most proliferative of all the lymphomas

IgM+, CD19+, CD10+, CD20+

non-treated: fatal in 6 months; treated: 90% cure rate

t(8:14)(c-myc:IgH)  t(8:2) IgKappa, t(8 :22) IgLambda

3.        Follicular Cell Center Lymphoma (FCCL)

morphology: nodular

size: small, cleaved

follicular growth pattern

painless adenopathy, B-symptoms

B-Cells (CD10+, CD19+, CD20+, CD5-)


don’t proliferate faster, but also don’t die (anti-apoptosis); resistant to chemotherapy

median survival: 5-8 years

cells become larger over time

4.        Diffuse Large B cell Lymphomas

morphology: diffuse

size: large

most common B-cell non-HL

CD10+/-, CD19+, CD20+

aggressive tumor (but aggressive tumors are usually more sensitive to chemotherapy!)


5.        Multiple Myeloma

monotypic Ig (usually IgG)

destructive bone lesions, renal (tubular) injury, amyloidosis, bacterial infections (may be fatal)

neoplastic cells may induce apoptosis in normal Ig cells

involves marrow but cells are probably of post follicular B-Cell origin

differentiate from benign monoclonal Ig’s (common in older patients)

benign do not have:

o         clumps of monotypic plasma cells in bone marrow

o         bone lesions,

o         depression of normal Ig


6.        Extranodal marginal zone lymphoma of mucosal associated tissue (MALT lymphoma)

extranodal lymphoid tissue (GI, bronchial, etc.: MALT)

size: small to medium

indolent B-Cell lymphoma (CD10-, CD19+, CD20+)


t(11:18), trisomy 3

tend to remain localized (may à Large cell lymphoma)

small to medium size

Derivation of lymphoid tissue:

a.        Peyer’s patches

b.        Hashimoto’s

c.        Sjogren’s (salivary gland)

d.        infection (H. pylori)

                                                       ii.      T-Cell Lymphomas

10-15% of lymphomas (rare)

divided into precursor (bone/thymus) and peripheral

tend to be more aggressive than B-Cell lymphomas


difficult to diagnose

·          rare

·          extranodal presentation

·          no histological or cytological markers

·          no immunologic markers of clonality

                                            most peripheral T-cell neoplasms show loss of one or more pan T cell antigens (CD2, CD3, CD5, CD7)

1.        T-lymphoblastic lymphoma/leukemia

precursor T-Cell neoplasm (TDT+)

size: small T-cells (mostly CD4+)

characteristic folded, ceribriform nucleus

similar to precursor T-cell acute leukemia (treated similarly)

classic presentation: mediastinal mass in adolescent male (thymus)

thymic tissue effaced

2.        Mycosis Fungoides (MF) and Sézary Syndrome

peripheral, Cutaneous

erythematous, pruritic (sun-protected) skin lesions


PCR demonstration of T-Cell clonality often required for diagnosis

Sézary Syndrome is a subtype of MF

§          circulating tumor cells

§          generalized erythroderma

3.        Peripheral T-cell lymphoma, unspecified

peripheral, nodal (lymphadenopathy)

mature T-cell (TdT-, CD2+, CD3+) may aberrantly miss a surface marker

paraneoplastic (eosinophilia, pruritis, hemophagocytic syndromes)

half of all peripheral T-Cell lymphomas

effacement of nodal architecture

size: small, intermediate, and large mixture

4.        Anaplastic Large Cell (Ki-1+) Lymphoma (ALCL)

peripheral, nodal

most common peripheral T cell lymphoma in children

mediastinum spared

bone marrow not involved

good prognosis

strongly expresses CD30, EMA

t(2;5)(ALK dysregulation: Anaplastic lymphoma kinase)

b.        Hodgkin’s Lymphoma

Reed-Sternberg cells (CD15+, CD30+, CD45-, CD20-)

15% of all lymphomas

Young adults

Contiguous structures affected

Localized, painless adenopathy


Rare neoplastic cells

>80% cure

Pain after alcohol consumption


Diagnosis based on two things:

1.        Reed-Sternberg cells (or variants)

·          neoplastic

·          stop codons render immunoglobulin (V)ariable regions non-functional

o         would normally be eliminated by apoptosis (unable à antigen affinity)

·          Forms of:

a.        classic: large, binucleate cell with eosinophilic cytoplasm

b.        lacunar: formalin artifact

c.        L&H (lymphocyte and histiocytes): popcorn cells, polylobulated nuclei

2.        Reactive cell background

                                                       ii.      Classical  HL

1.        Nodular Sclerosing Hodgkin’s Lymphoma (NSHL)

lacunar RS cells

most common type of HL

younger age: 25

only type that affects females > males

cervical lymphadenopathy, mediastinal mass

B-Symptoms: night sweats, fever, weight loss (1/3 of patients)

Broad bands of collagen, capsular fibrosis

T-Cell and Eosinophil infiltrate

2.        Mixed Cellularity Hodgkin’s Lymphoma (MCHL)

second-most common

young men


Multiple nodes (stage III, IV)

good prognosis

classic RS cells

EBV virus most closely associated

3.        Lymphocyte Rich Classical Hodgkin Lymphoma (LRCHL)

Lack B-Symptoms

diffuse, small lymphocytes

L&H RS cells

4.        Lymphocyte Depleted Hodgkin's Lymphoma (LDHL)


Most aggressive LDHL


RS Cells predominate

classicàbizarre RS cells

                                                     iii.      Non-Classical HL

1.        NLPHD

L&H RS cells: popcorn cells, polylobulated nuclei (NLPHL)

CD30-, CD45+

Lack B-Symptoms

cervical or axillary

good prognosis if Stage I

à Large B Cell Lymphomas

small B-lymphocyte reactive background greatly outnumber RS cells

Hematopoietic System

Bone marrow: Hemopoiesis

Four committed progenitor cell lines

1.        erythroid (RBC)

2.        megakaryocytic (megakaryocyte)

3.        granulocytic-monocytic (monocyte, neutrophil, basophil, eosinophils, mast cell)

4.        lymphocytic (T,B,NK)


Lymphoid System

Lymphoid organs

1.        lymph nodes

2.        thymus

3.        spleen

4.        adenoids

5.        MALT (mucosal associated lymphoid tissue); GI, lung, marrow, skin



Lymphocytes made in bone marrow


·          T-Cells: thymus (à T-helper=CD4+, T-cytotoxic=CD8)

·          B-Cells : bone marrow (become plasma cells in lymph tissue)

Migrate to peripheral lymph tissues


Lymph Nodes

Meeting place for T and B cells

·          Lymphocytes: through high endothelial venules from blood

·          Antigens: lymphatic vessels


1.        Lymphoid follicles: clonal expansion B-Cells and plasma cells/memory cells

2.        Marginal zone: immature B-Cells (unchallenged by antigen)

3.        Parafollicular cortex: T-Cells




1.        red pulp: filtering component

2.        white pulp: lymphoid component

a.        B-Cell domains: similar to lymphoid follicles

b.        Periarteriolar lymphoid sheath: T-dependent areas


Disorders (General info.)

·          Disorders can be reactive or neoplastic

·          Marrow-based reactive disorders

o         Leukocytosis

1.        neutrophilia: bacteria

2.        eosinophilia: allergy, parasites

3.        monocytosis: chronic infections

4.        leukemoid reaction: severe infection

a.        immature myeloid precursors can be in circulation

o         Cytopenias

1.        aplastic anemia (benzene exposure)

·          Lymph node-based reactive disorders

1.        toxoplasmosis

2.        infectious mononucleosis

3.        cat scratch disease: focal abscesses

·          Neoplasms

1.        Leukemias: marrow

a.        lymphocytic or myeloid

b.        acute or chronic

2.        Lymphomas: non-marrow (neoplastic cells tend to resemble phenotype)

a.        Hodgkin’s and Non-Hodgkin’s [NHL: B (80-85%), T, NK (rare) cell types]

3.        Other neoplasms of marrow

a.        Myelodysplastic Disorders (clonal, hypercellular marrow, dysplastic cytologic features, peripheral cytopenias, anemia)

b.        Myeloproliferative Disorders (clonal, hypercellular marrow, no dysplasia, increased peripheral counts)


Lab Test


1.        Peripheral blood draw

2.        Bone marrow aspirate

3.        Lymph node fine needle aspiration

4.        Lymph node biopsy

5.        Other biopsy

Morphologic examination

1.        Wright’s stain (number, morphology, types of cells)

2.        H&E: (architecture of tissue)

Flow Cytometry

·          most commonly used technique to examine surface antigens

·          separate out before based on scales of size and complexity (lymphocytes have smallest size and least complexity)

·          fluorochrome-conjugated antibodies (lineage/maturation)

Immunohistochemical stains

·          clonality of B-Cells

·          T-cell phenotype

Cytochemical studies

·          Myeloid: Sudan black (SB), Myeloperoxidase (MPO), Specific Esterase (SE): react with granules

·          Lymphoid: non-specific esterase (NSE)

Cytogenetic studies

·          G-banding (karyotype) during metaphase (only possible when sample is large enough and able to divide)

·          FISH (fluorescent in situ hybridization) picks up small translocations

o         red, green, yellow (should be two red, two green; translocation: one red, one green, one yellow)

Molecular studies

·          Reactive: polyclonal smear

·          Neoplastic: monoclonal band