ABPath Hematopathology flashcards

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Bone marrow cellularity estimate

Cellularity is estimated as 100 minus the patient's age in years; a 60-year-old therefore has approximately 40% marrow cellularity.

M:E ratio

The ratio of myeloid to erythroid cells in marrow; normal is 2:1 to 4:1, increased in granulocytic hyperplasia and decreased in erythroid hyperplasia.

Reticulin fibrosis grading

Bone marrow reticulin is graded MF-0 to MF-3; MF-2 shows diffuse dense reticulin, and MF-3 adds collagen fibrosis or osteosclerosis.

Blast percentage threshold

Acute leukemia is generally diagnosed when blasts are at least 20% of blood or marrow cells, except APL with t(15;17), which is diagnostic regardless.

Embryonic hematopoiesis sites

Hematopoiesis begins in the yolk sac at about 3 weeks, moves to the liver by 6 weeks, and to bone marrow by 20 weeks of gestation.

Hemoglobin switching

Embryonic hemoglobins are replaced by fetal HbF (alpha2 gamma2), then by adult HbA (alpha2 beta2) after birth; adult HbF is below 2%.

CD34 stem cell marker

CD34 identifies hematopoietic stem and progenitor cells; lineage markers include CD19 for B cells, CD3 for T cells, and CD13/CD33 for myeloid cells.

Clonal hematopoiesis of indeterminate potential

CHIP is a somatic mutation with variant allele frequency at least 2% in blood or marrow without cytopenia or dysplasia; common genes are DNMT3A, TET2, ASXL1.

Reticulocyte index formula

Reticulocyte index equals reticulocyte percentage multiplied by patient hematocrit divided by normal hematocrit; a value above 2 suggests adequate marrow response.

Iron deficiency ferritin cutoff

Serum ferritin below 30 ng/mL strongly supports iron deficiency; ferritin is an acute-phase reactant and may be normal or high with inflammation.

Warm autoimmune hemolytic anemia

Warm AIHA is caused by IgG antibodies that bind red cells at 37 degrees Celsius; the direct antiglobulin test is positive for IgG, and spherocytes are seen.

Paroxysmal nocturnal hemoglobinuria flow

PNH is diagnosed by flow cytometry showing loss of CD55 and CD59 on red cells and loss of CD24 or CD14 on granulocytes.

Absolute neutrophil count

ANC equals the white blood cell count multiplied by the percentage of segmented plus band neutrophils; severe neutropenia is ANC below 500/microliter.

CML genetic hallmark

Chronic myeloid leukemia is defined by t(9;22) forming BCR::ABL1; the smear shows basophilia and a full myeloid left shift.

Acute promyelocytic leukemia

APL has t(15;17) PML::RARA, often with DIC and Auer rods; it is treated urgently with ATRA and arsenic trioxide.

MDS ring sideroblast threshold

Ring sideroblasts are erythroid precursors with at least five iron granules encircling one-third of the nucleus; at least 5% supports MDS with SF3B1 mutation.

CLL immunophenotype

CLL cells are CD5 positive, CD23 positive, CD20 dim, and surface immunoglobulin dim; smudge cells are common on the blood smear.

Mantle cell lymphoma marker

Mantle cell lymphoma is CD5 positive, CD23 negative, and cyclin D1 positive due to t(11;14); it is generally more aggressive than CLL.

Hairy cell leukemia markers

Hairy cell leukemia expresses CD11c, CD25, CD103, and CD123; it is TRAP positive and commonly has BRAF V600E mutation.

Hodgkin Reed-Sternberg phenotype

Classic Reed-Sternberg cells are CD15 positive, CD30 positive, CD45 negative, and PAX5 weak; nodular sclerosis is the most common subtype.

Aplastic anemia diagnostic criteria

Aplastic anemia shows pancytopenia with a hypocellular marrow; cellularity is below 25%, or below 30% with less than 50% residual hematopoietic cells.

Leukoerythroblastic smear

A leukoerythroblastic smear shows nucleated red cells and immature myeloid cells in blood; causes include marrow infiltration, myelofibrosis, and severe hemolysis.

HLH diagnostic criteria

HLH requires five of eight criteria: fever, splenomegaly, cytopenias, hypertriglyceridemia or hypofibrinogenemia, hemophagocytosis, low NK activity, high ferritin, high sIL-2R.

ITP treatment threshold

Immune thrombocytopenia usually requires treatment when platelets are below 30,000/microliter or when bleeding occurs; first-line options are corticosteroids and IVIG.

TTP ADAMTS13 cutoff

Thrombotic thrombocytopenic purpura is diagnosed when ADAMTS13 activity is below 10%; treatment is urgent plasma exchange, not platelet transfusion.

HIT 4Ts score

The 4Ts score estimates heparin-induced thrombocytopenia probability using thrombocytopenia degree, timing, thrombosis, and other causes; stop heparin if intermediate or high.

Glanzmann thrombasthenia defect

Glanzmann thrombasthenia is a deficiency of platelet glycoprotein IIb/IIIa; platelets fail to aggregate with all agonists except ristocetin, and count is normal.

PT versus aPTT

PT measures extrinsic and common pathway factors, while aPTT measures intrinsic and common pathway factors; mixing studies distinguish factor deficiency from inhibitor.

Factor V Leiden

Factor V Leiden causes activated protein C resistance from a G1691A mutation; it is the most common inherited thrombophilia and increases venous thrombosis risk.

DIC laboratory pattern

Disseminated intravascular coagulation shows prolonged PT and aPTT, low fibrinogen, elevated D-dimer, thrombocytopenia, and schistocytes on the blood smear.

Restrictive transfusion threshold

For stable hospitalized adults, red cell transfusion is generally indicated when hemoglobin is below 7 g/dL; a threshold of 8 g/dL is used for cardiac surgery.

Platelet transfusion prophylaxis

Prophylactic platelet transfusion is typically given when the count is below 10,000/microliter; it is avoided in TTP and HIT unless active bleeding is present.