Bone Marrow

Question 1

Hematopoiesis

Answer 1

Myeloid stem cell —> RBC, granulocytes, monocytes, platelets

Question 2

Lymphopoiesis

Answer 2

Lymphoid stem cell —> T cell, B cell, plasma cell

Question 3

Erythropoiesis

Answer 3

Erythropoietin (from kidney) regulates RBC production
Hypoxia (or ILs, CSFs, hormones) —> Epo release

Question 4

Granulopoiesis

Answer 4

Myeloid series production (granulocytic + Monocytic cells)

Inflammatory mediators (ILs, TNFa) —> cytokine (G-CSF, GM-CSF) production —> stimulate granulopoiesis + monocytopoiesis

Question 5

Megakaryopoiesis

Answer 5

Thrombopoietin (Tpo) by liver regulates thrombopoiesis (constitutively produced)

Megakaryocytes —> endomitosis to become polyploid —> extend into bone marrow venous sinusoids —> fragment to platelets

Question 6

Cytology

Answer 6

Identification of cell types within tissue or fluid by evaluation of smears made from specimen

Faster than biopsy, more detail of internal cell structures

Sacrifices anatomic relationship

Question 7

Core biopsy

Answer 7

Histologic assessment

Definitive determination of cellularity and fibrosis

Within the environment of tissue

Question 8

Dynamic nature of bone marrow

Answer 8

Peripheral demands for WBC/RBC/platelets —> shift in bone marrow cytologies profiles due to hyperplastic responses

Disease of bone marrow —> impacts peripheral leukocyte, erythrocyte, platelet numbers

Question 9

Reasons to evaluate bone marrow

Answer 9

Unexplained/persistent dec or inc in particular cell line
Abnormal or immature cells in circulation
Atypical cell reactions
FUO
Unexplained lab findings - hypercalcemia, hyperglobulinemia
Staging of neoplasia - lymphoma or mast cell tumors

NEED CONCURRENT CBC

Question 10

Indications for core biopsy

Answer 10

Bone changes
Abnormal bone marrow cellularity (hypo/hyper cellular, aplasia)
Focal lesions
Unsuccessful aspiration

Question 11

Parameters to evaluate in bone marrow

Answer 11

Cellularity + particles
Maturation sequences + morphology
Frequency of lymphocytes, macs, plasma cells, other cells
Adequacy of iron
Presence of abnormal cells

MYELOID:ERYTHROID ratio (M:E)!!

Question 12

Erythroid series

Answer 12

Rubriblast —> prorubricyte —> rubricyte —> metarubricyte —> polychromatophil —> RBC

Question 13

Myeloid series

Answer 13

Progranulocyte —> myelocyte —> metamyelocyte —> band cell —> neutrophil, eosinophils, basophil

Question 14

Hyperplasia

Answer 14

Increase in response to peripheral demand for specific cell type

PREDICTIBLE

Question 15

Causes of erythroid hyperplasia

Answer 15

Hemorrhage (trauma, coagulopathies, neoplasia)
Hemolysis (IMHA, toxin, infectious, oxidant injury, enzyme deficiencies, hypophosphatemia)

Question 16

Trigger for erythropoiesis

Answer 16

Low Hb —> hypoxemia —> Epo by kidneys —> erythropoiesis in marrow

Question 17

Clinical indication of erythroid hyperplasia

Answer 17

M:E decreases, immature RBC in blood (polychromatophilic RBC - bluish cells, and reticulocytes in blood)

Question 18

Response to acute severe hemolysis or hemorrhage

Answer 18

Abrupt decrease in hemoglobin —> immediate tissue oxygen compromise —> tissue necrosis —> concurrent myeloid hyperplasia —> peripheral leukocytosis

M:E may be normal with increase in both myeloid + erythroid line

CONCURRENT CBC required for M:E evaluation

Question 19

Myeloid hyperplasia

Answer 19

Response to increased need for granulocytes and/or monocytes (i.e. infection)

M:E increases

Immature cells in blood increase with “left shift” in maturation

Question 20

Megakaryocytic hyperplasia

Answer 20

In response to destruction, loss consumption of platelets
(Immune mediated disease, DIC)

Question 21

Bone marrow hypoplasia

Answer 21

Hypoplasia of a cell line results in peripheral decrease in that cell type

Clinical signs reflect missing cell type

Question 22

Causes of bone marrow hypoplasia

Answer 22

Anemia of chronic disease / inflammation
Immune-mediated
Cytotoxic or drug-induced
Infection (viral)
Endocrine-induced
Iron deficiency
Renal failure
Malnutrition
Inherited disorders
Idiopathic

Question 23

Anemia of chronic disease or inflammation

Answer 23

Bone marrow hypoplasia
Most common cause of non regenerative anemia

Not as predictible as hyperplasia

Question 24

Types of bone marrow inflammation

Answer 24

Acute myelitis
Granulomatous or pyogranulomatous

Question 25

Myelodysplastic Syndrome

Answer 25

Group of Clonal myeloid proliferative disorders Abnormal cell morphology Marrow profile indicates hyperplasia of one or more cell line without improvement in peripheral cell count Can be associated with FeLV, FIV

Question 26

Leukemia

Answer 26

Malignant hematopoietic neoplasm originating in bone marrow OFten significant number of neoplastic cells in blood Lymphocytic or myelogenous, acute or chronic

Question 27

Myelogenous leukemia

Answer 27

AML: peripheral blood smear with blast cells, lack of appropriate maturation of marrow cells, most common in FeLV cats; poor prognosis CML: high peripheral cell count, normal morphology (process of elimination diagnosis); rare, chronic,

Question 28

Lymphoid leukemia

Answer 28

ALL: immature lymphocytes, may efface marrow, young to middle aged CLL: well-differentiated lymphocytes, usually do not efface marrow, usually older animals

Question 29

Multiple myeloma

Answer 29

Plasma cell neoplasm in marrow, malignant

Question 30

Myelofibrosis

Answer 30

Generally secondary (scar formation, GF-induced fibroblast proliferation) Difficult to aspirate Histologic diagnosis