Evaluation of Bone Marrow

What are the three main cell lineages that tell us about marrow function?

neutrophils, platelets, erythrocytes

What indicates a need for marrow examination?

prolonged peripheral cytopenias that cannot be explained by mechanisms of peripheral destruction (non-regenerative anemia, thrombocytopenia, neutropenia; bi/pancytopenia)

What are venous sinuses lined by?

blood:marrow barrier

What is the organization of marrow?

hematopoietic tissue supported by reticular stroma and adipocytes

What is the relationship of hemotopoietic cells and amount of fat in the marrow?

inverse relationship; fat accumulates if hematopoiesis decreases and catabolizes to accommodate an increase in hematopoiesis (example 25% to 75%)

What causes direct thermal injury to endothelial cells and results in loss of blood-marrow barrier integrity?

heat stroke

What is the hallmark sign of heat stroke?

inappropriate rubricytosis; increased nRBCs in circulation in the absence of anemia

What are the advantages of aspirate?

easier, quicker, cheaper, better cytomorphologic detail

What are the advantages of core biopsies?

can assess architectural abnormalities, cellularity and megakaryocyte number is more accurate

Which one is ideal? Aspirate or core biopsy?

collect and evaluate both together

What is the entire microscopic structure of hematopoietic cells with associated stroma (adipocytes) called?

particle or spicule

What is the site of active hematopoiesis?

active “red” marrow; amount decreases into metaphyses with age

What is inactive “yellow” marrow?

composed predominantly of adipose tissue found in diaphyses; increases with age

What are the marrow collection sites for dogs and cats?

iliac crest, proximal humerus, and trochanteric fossa of the femur

What are the marrow collection sites for large animals?

sternum and rub

What region of the bone should you target for marrow collection? Why?

metaphyseal region because diaphyseal samples have marked fat infiltration and will. not represent active hematopoiesis

True or False: Sedation and/or anesthesia is required for marrow collection.

True

What must be submitted with marrow samples?

complete CBC obtained within 24 hours of marrow collection

What is cellularity?

particle composition that decreases with age

What cellularity percentage do young animals have?

75%

What cellularity percentage do adult animals have?

25%

What is the best method for megakaryocyte assesement?

core biopsy

What is stainable iron?

marrow storage of iron

In what animals is stainable iron a good indicator of total body iron?

dogs, cattle, horses

In what animals is stainable iron not a good indicator of total body iron?

cats because they lack this in marrow

What is a decreased stainable iron a sign of?

iron deficiency

What is an increased stainable iron a sign of?

anemia of inflammation, hemosiderosis from IMHA, etc

What is the myeloid-to-erythroid ratio (M:E)?

more accurate to call granulocytic-to-erythroid ratio

What does hyperplasia of erythroid, granulocytic, or megakaryocytic series indicate?

increased numbers of precursor stages of RBCs, neutrophils, and platelets, repectively

What is an erythroid hyperplasia characterized by?

low M:E and hypercellular marrow

What is an granulocytic hyperplasia characterized by?

high M:E and hypercellular marrow

What is an megakaryocytic hyperplasia characterized by?

increased numbers of megakaryocytes; M:E not involved here

What are the causes of erythoid hyperplasia?

hemolytic anemias, late-stage PIMA, chronic blood loss, iron deficiency anemia

What are the causes of granulocytic hyperplasia?

infections, tissue necrosis, generalized inflammatory disease

What are the causes of megakaryocytic hyperplasia?

immune-mediated thrombocytopenia (ITP), rickettsial infections, DIC

What is hypoplasia?

fewer precursor cells than appropriate for the number of mature cells in peripheral blood

What is an erythroid hypoplasia characterized by?

high M:E and hypocellular or normocellular marrow

What is an granulocytic hypoplasia characterized by?

low M:E and hypocellular or normocellular marrow

What are the causes of erythroid hypoplasia?

early-stage PIMA, inflammation, hypothyroidism, hypoadrenocorticism

What are the causes of granulocytic hypoplasia?

immune-mediated neutropenia, infections, drug/toxins, cyclic neutropenia of gray collies

What is aplasic anemia?

marrow is fatty/nearly devoid of hematopoietic cells (all three cell lines); aka aplastic pancytopenia

What is the causes of aplastic anemia?

estrogen, TMS, chemotherapeutics, bracken fern toxicosis in cattle, radiation

What is the bacteria infectious agent in the marrow?

mycobacterium (non-staining rods)

What is the protozoa infectious agent in the marrow?

leishmania, cytauxzoon felix

What is the fungus infectious agent in the marrow?

histoplasma

What are the common neoplastic cells in marrow?

lymphoid/myeloid leukemia, lymphoma, and multiple myeloma

What is myelofibrosis?

marrow replaced by collagen, can only be diagnosed on core biopsy and is suspected when aspirate yields “dry” tap

Myelofibrosis is typically a secondary process for?

PIMA