hemopathology - patho.szote.u

HEMOPATHOLOGY
Adult hemopoietic stem cells
• Ability to self-renew and to differentiate into
erythroid, myeloid, and megakaryocytic cell lineages
• Occur in specialized microenvironments of the bone
marrow (stem cell niches)
• Travel in the blood from the bone marrow in one
bone to another bone; may settle in the liver and
spleen (extramedullary hemopoiesis)
• Morph.: small cells with a rounded nucleus and lowcytoplasm-to-nucleus ratio; lack of lineage markers;
not possible to identify them by conventional LM
• HSCs constitute 1:10.000 of cells in myeloid tissue
Constituents of bone marrow
Stem cell compartment
Repopulating stem cells and restricted
progenitors
Differentiated cell compartment
Ba
myeloblast
Ba
gr
Eo
myeloblast
Eo
gr
Myelo
(mono)blast
Neu Mo
gr
Megakaryoblast
Pronormoblast
Megakaryocyte
Erythrocyte
Trephine biopsy to investigate the constituents of
bone marrow
Trephine biopsy: elements of normal hemopoiesis
Constituents of bone marrow
Stem cell compartment
Repopulating stem cells and restricted
progenitors
Differentiated cell compartment
Ba
myeloblast
Ba
gr
Eo
myeloblast
Eo
gr
Myelo
(mono)blast
Neu Mo
gr
Megakaryoblast
Pronormoblast
Megakaryocyte
Erythrocyte
Peripheral blood
From bone marrow: granulocytes, thrombocytes, RBCs;
from lymphoid tissues: lymphocytes, NK cells
ANEMIA
A decrease in the RBC mass and the hemoglobin
content in the blood
All anemia evaluations should include
• Erythrocyte count
• Hemoglobin level (normal: 7.4-11.2 mmol/L))
• Hematocrit (normal: 36%-49%)
• Mean corpuscular volume (MCV;
hematocrit/erythrocyte count)
• Peripheral blood smear
Anemias according to red cell size
•Normocytic (normal) – diverse etiologies
•Microcytic (smaller) – disorders of hemoglobin
synthesis
•Macrocytic (larger) – abnormalities in bone marrow
erythroid precursor maturation
Normocytic anemia
Smear: normal RBC morph.; MCV: 80 -100 fL
Common causes
• Decreased production due to bone marrow
failure (aplastic anemia, myelofibrosis) or
tumorous infiltration of bone marrow (leukemia,
lymphoma, myeloma, carcinoma metastases)
• Increased destruction due to hemolysis
(autoimmune hemolytic anaemia, sickle cell
anemia, Plasmodium falciparum malaria, etc.)
• Decreased stimulation:  erythropoietin in
bilateral chronic renal disease
Evidences of hemolysis
Jaundice
Serum
• Elevation of unconjugated bilirubin
• Raised lactic dehydrogenase (LDH) released from
ruptured RBCs
• Reduced haptoglobin (liberated hemoglobin is
initially bound to plasma haptoglobins but these
soon become saturated; hemoglobin-haptoglobin
complexes are removed from the circulation by
the liver)
Urine: excess urobilinogen resulting from bilirubin
breakdown in the intestine
Microcytic anemia
Smear: smaller RBCs; MCV < 80 fL
Common causes
1. Iron deficiency
• Chronic blood loss: GI ulcer/cc, gynecologic
disturbances, renal cell cc
• Increased requirement: pregnancy
• Decreased absorption: sprue, Crohn’s disease
2. Anemia of chronic disease
• Increased IL-6 hepatic hepcidin synthesis
high levels of plasma hepcidin, which blocks the
transfer of iron to erythroid precursors from
duodenal epithelium and macrophages.
• Collagen-vascular disease, infection, sarcoidosis,
etc.
Macrocytic anemia
Smear: enlarged RBCs; MCV >100 fL
Causes
• Megaloblastic bone marrow in pernicious anemia:
vitamin B12/folate deficiency. Basis of pernicious
anemia: autoimmune chronic atrophic gastritis of
corpus of stomach  loss of intrinsic factor
production
• Normoblastic bone marrow: chronic alcoholics, liver
disease
APLASTIC ANEMIA
Misleading term applied to a sy of bone marrow failure
due to the suppression of trilineage myeloid stem
cells  pancytopenia
Aplastic anemia: suppression
of myeloid stem cells
Ba
myelo
blast
Ba
gr
Eo
myelo
blast
Myelo
(mono)
blast
Eo Ne Mo
gr gr
Megakaryoblast
Pronormoblast
Mega- Erythkaryo- rocyte
cyte
Granulopenia, thrombopenia,
anemia
Pathogenesis
• Idiopathic - 65%: T-cell mediated autoimmune
suppression of stem cells; intrinsic abnormality of
stem cells; defective hemopoietic
microenvironment
• Secondary to cytotoxic drugs, chemicals
(benzene, insecticides), viral infections (hepatitis,
HIV, EBV, CMV), whole body irradiation
Gross: yellow fatty marrow at sites of red bone marrow (top: femur, bottom: sternum)
LM of bone marrow: hypocellular; composed of fat cells and
a few ly-s; hemopoietic cells are rare or absent
Clinical features
May occur at any age
Gradual onset of anemia  progressive weakness,
cutaneous and conjunctival pallor, and dyspnoea;
thrombopenia  spontaneous bleedings:
petechiae, ecchymoses, gingival haemorrhages;
granulopenia  bacterial infections: ulcerative
gingivitis/pharyngitis, pneumonias, colitis, cystitis
No splenomegaly
Prognosis: variable, bone marrow Tx or
immunosuppressive th may be beneficial
Diff. dg.: from other causes of pancytopenia
•
•
•
•
Acute aleukemic leukemia
Myelodysplastic sy
Lymphoma in bone marrow spaces
Cc metastases in bone marrow spaces (lung,
breast, prostate)
Prostate carcinoma metastases in spine and femur
(bottom: normal trabecular structure after formol
fixation)
MYELOID NEOPLASIAS
General features
• Malignant clonal disorders of hemopoietic stem
cell/restricted progenitors
• Arise in the bone marrow and involve the sec.
hemopoietic organs (spleen, liver, lymph nodes)
• The symptoms are related to the suppression of
normal hemopoiesis (e.g., anemia, infection
and/or bleeding)
• May produce neoplastic leukocytosis in the blood
Classification
1) Acute myeloid leukemia
3) Chronic myeloproliferative disorders
3) Myelodysplastic syndromes
ACUTE MYELOID LEUKEMIA (AML)
• In any age; affects primarily adults
• Peak: 60 years of age
• Highly malignant
Pathogenesis
• Hemopoietic stem cell/restricted progenitors gain
oncogenic mutations which interfere with
transcription factor activities required for normal
myeloid cell differentiation
• E.g.,: in acute promyelocytic leukemia, a t(15;17;)
translocation results in the fusion of the retinoic
acid receptor-α gene (RARA) on chromosome 17
to the promyelocytic leukemia (PML) gene on
chromosome 15  the fusion product blocks
myeloid cell differentiation
• Gradual replacement of bone marrow cells with
immature leukemic myeloblasts
These blasts
• suffer additional mutations
• spill over into the blood  leukemic blood picture
• suppress non-mutated stem cells  declining
normal hemopoiesis
Morphology
Gross
Long bones: yellow blood marrow is replaced by
tumorous red bone marrow
LM
Bone marrow
Diagnostic criterion: more than 20% blasts.
• The cytoplasm of the blasts contain
myeloperoxidase-positive granules
• The blasts may exhibit myelomonocytic,
monocytic, erythroid or megakaryocytic
maturation
Grossly, the sites of yellow bone marrow are infiltrated by tumorous red bone
marrow.
Top: in AML, the diaphysis is replaced by leukemic red bone marrow.
Bottom: normally, the diaphysis of femur is filled with yellow fatty bone
marrow.
AML: leukemic myeloblasts among cells of normal hemopoiesis
AML: the marrow is massively infiltrated by myeloperoxidase-positive myeloblasts
(Giemsa)
Peripheral blood
• 10.000 to 100.000 WBCs/ul (smear: the majority
are myeloblasts)
• On occasion, the patient may have pancytopenia,
and the smear does not contain any blasts
(aleukemic leukemia; marrow biopsy is required for
the dg)
AML; blood smear: the majority of nucleated cells are immature myeloblasts
Clinical features
• Most patients are presented with consequences of
anemia, granulopenia, and thrombopenia + mild
leukemic infiltration of liver (hepatomegaly), spleen
(splenomegaly) + lymph nodes (lymphadenomegaly)
• Procoagulants released by leukemic cells can
produce DIC – feature of AML with promyelocytic
differentiation
• Gingival and skin infiltration (leukemia cutis) –
feature of AML with monocytic differentiation
Outcome
• Variable, depends on AML subtype, rapidly fatal if
left untreated
• Overall 5-y-survival rate ranges between 15%-30%
• Death from thrombopenic hemorrhages (CNS, lungs,
GI) or from bacterial or fungal infections
In promyelocytic leukemia, the PML/RARA fusion
protein can be blocked with all-trans retinoic acid
(ATRA) + arsenic trioxide producing cure in the majority
of patients
CHRONIC MYELOPROLIFERATIVE
DISEASES
•
•
•
•
Chronic myeloid leukemia
Polycythemia vera
Essential thrombocytosis
Myelofibrosis
Common features
• Mutation of stem cell leading to the presence of
constitutively active tyrosine kinases that induce
growth-factor independent proliferation and survival
of marrow progenitors which retain maturation
capacity
• The neoplastic stem cells infiltrate the marrow and
suppress the stem cells of normal hemopoiesis
• The neoplastic stem cells settle down in the sec.
hemopoietic organs and produce extramedullary
hemopoiesis, particularly in the
spleen(splenomegaly)
• MPDs may progress over time to AML or terminate
in a spent phase  bone marrow fibrosis and
pancytopenia
Chronic myeloid leukemia (CML)
• Malignant neoplasm of hemopoietic stem cell
leading to preferential proliferation of granulocytic
progenitors
• Disease primarily of adults; peak: between 50-60 ys
Pathogenesis
• Translocation involving the BCR (Breakpoint cluster
Region) gene on chromosome 22 and the ABL
(Abelson leukemia virus) gene on chromosome 9
•
• The BCR-ABL fusion gene directs the synthesis of a
protein with tyrosine kinase activity: increased
proliferation and decreased apoptosis of maturing
granulocytic progenitors
• t[9.22] translocation: designated as Philadelphia
chromosome
Translocation involving the BCR gene on chrom. 22 and the ABL gene on
chrom. 9. The BCR-ABL fusion gene directs the synthesis of a protein
with tyrosine kinase activity
Kumar et al. Pathologic Basis of Disease, Elsevier, 2005
Morphology
• Bone marrow: hypercellular, no fat cells;
granulopoiesis predominates
• Blood: up to 300000 WBC/ul (ng-s, metamyelocytes,
myelocytes, and <10% myeloblasts), anemia
• Neoplastic extramedullary hemopoiesis: massive
splenomegaly, hepatomegaly, + lymphadenomegaly
Clinical course
• Chronic phase (lasts for years): weight loss, fatigue,
malaise, fever, and sweating; splenomegaly (up to
3000 grams; fills the abdominal cavity and extends into
the pelvis + infarcts)  left upper quadrant pain
• Accelerated phase: increasing severity of anemia
and thrombopenia; myeloblasts start to  in the bone
marrow and blood
• Fatal blast crisis phase: features of AML; death:
from infections or thrombopenic hemorrhage
Tyrosin kinase inhibitor imatinib markedly decreases
(but does not eliminate) the number of BCR-ABLpositive cells and yields sustained remission in 90%
of
patients if administered in the chronic phase
Polycythemia vera (PV)
Pathogenesis
• Increased marrow production of erythrocytes,
granulocytes, and platelets because of activating
point mutations in the JAK2 tyrosine kinase that
participates in JAK/STAT signaling pathways.
• The  in red cell mass is responsible for most of the
clinical symptoms
Morphology
• Bone marrow:  proliferation of erythroid,
granulocytic and megakaryocytic elements
• Pancytosis in the blood: erythrocytosis (polycythemia;
hematocrit > 60%), granulocytosis, thrombocytosis
Clinical features
•
•
•
•
Onset: around 60 ys
Skin: plethoric and cyanotic; itching
High blood viscosity: headache, dizziness
Risk of thrombotic episodes (deep veins, sinuses of
the brain, coronaries)
• Splenomegaly
• Hypertension in most patients
• Epistaxis and bleeding gums because of platelet
dysfunction
Outcome
• Phlebotomy to normalize the hematocrit results in
median survival of 10 ys
• Transformation to AML: infrequent
• Left-sided heart failure because of blood
hyperviscosity
Essential thrombocytosis (ET)
Pathogenesis
• In majority of patients: activating point mutations
in JAK2
• In minority of patients: activating point mutations
in MPL, a tyrosine kinase that is normaly activated
by thrombopoietin
• These mutations induce the hyperproliferation of
the megakaryocytic lineage
Morphology
• Bone marrow: significantly increased number of
megakaryocytes, often abnormally large
• Blood: thrombocytosis, abnormally large platelets,
mild leukocytosis
Trephine biopsy in ET: abnormal megakaryocytes
Clinical features
• Asymptomatic for several years, indolent course
• Erythromelalgia: throbbing and burning of hands
and feet caused by occlusion of small arteries by
platelet aggregates
• Paradoxical hemorrhagic complications
• Progression to myelofibrosis or transformation to
AML: infrequent
MYELOFIBROSIS (MF)
Development of obliterative marrow fibrosis 
diminished hemopoiesis  cytopenias in the
blood + extensive extramedullary hemopoiesis
Pathogenesis
Two subsets:
Primary MF:
• JAK2 mutations or MPL mutations (in minority of
patients); release of PDGF and/or TGF-beta from
neoplastic megakaryocytes  marrow fibrosis
• Secondary MF: spent phase of PV or ET
Morphology
• Trephine biopsy: variable cellularity with
increased reticulin, progressing to massive
deposition of collagen
• Late in the course, the fibrotic marrow space can
convert to bone (osteosclerosis)  bone marrow
cannot be aspirated!
• Hemopoiesis is displaced to the spleen and liver
(myeloid metaplasia)  massive splenomegaly
(more than 4000 g) and hepatomegaly
Myelofibrosis: accumulation of reticulin fibers in marrow spaces
Myelofibrosis: the bone trabeculae are thickened,
the marrow spaces are narrowed and display fibrosis
Myelofibrosis (right): osteosclerosis of the marrow spaces of
sternum. Right: normal sternum
Myelofibrosis.
Note extreme splenomegaly
induced by extramedullary
hemopoiesis (myeloid metaplasia).
The arrow indicates spontaneous
infarction of the spleen
parenchyma.
Liver
The patient died of
consequences of transformation
to acute myeloid leukemia.
Spleen
Stomach
Blood
• Anemia, tear-drop erythrocytes (dacrocytes)
• Normal or reduced WC count
• (quali: presence of granulocytic and erythroid
precursors [leukoerythroblastosis])
• Large platelets, later thrombopenia
Clinical features of primary MF
• Insidious onset in individuals older than 60 ys
• With blood transfusions, survival is often a few
years
MYELODYSPLASTIC SYNDROME (MDS)
Hemopoietic stem cell neoplasm characterized by
ineffective hemopoiesis manifesting as cytopenia(s),
morphologically dysplastic hemopoietic cells, and a
high risk of transformation to AML.
Pathogenesis
Not fully understood
• The bone marrow is partly or wholly replaced by the
clonal progeny of a mutant multipotent stem cell that
retains the capacity to differentiate into red cells,
granulocytes, and platelets.
• However, the differentiation process is ineffective
and disordered.
• Bone marrow stromal cells induce increased
apoptosis in more mature hemopoietic precursors,
accounting for the cytopenia(s).
Classification
• Primary MDS: affects people above 50 ys, insidious
development
• Therapy-related (t-MDS): complication of
myelosuppressive drug or radiation therapy; 2-8 ys
after exposure
Morphology
Bone marrow: hypercellular or normocellular
Dysplasia affecting all three lineages:
- ringed sideroblasts (erythroid progenitors with ironladen mitochondria [blue granules in Prussian blue
stain])
- neutrophils with little granulation and abnormal
nuclear features
- hypolobated or hyperlobated megakaryocytes
Blood: cytopenia(s)
Clinical features
• Pancytopenia-related weakness, infections,
haemorrhages
• Progression to AML in 10-40% of patients; some
die of bleeding or infection
• Median survival in primary MDS: 9 to 29 mo, in tMDS: 4 to 8 mo