Leukemias – Core Vocabulary Review

Thirty key vocabulary flashcards covering definitions, stains, mutations, and disease entities essential for mastering leukemia classification and diagnosis.

Leukemia

Clonal malignant disorder with uncontrolled proliferation and/or accumulation of hematopoietic cells in bone marrow, blood, and extramedullary organs, causing cytopenias and organ infiltration.

Cytopenia

Deficiency of one or more blood cell lines (anemia, neutropenia, thrombocytopenia) due to marrow failure or infiltration.

Blast Crisis

Aggressive, acute phase of a chronic leukemia (especially CML) marked by ≥20% blasts in blood or marrow.

Acute Myeloid Leukemia (AML)

Acute leukemia of myeloid lineage characterized by ≥20% myeloblasts in marrow/blood; subtyped mainly by genetic abnormalities in WHO 2022.

Acute Lymphoblastic Leukemia (ALL)

Acute malignancy of immature lymphoid cells (B- or T-lineage) with ≥20% lymphoblasts; most common childhood cancer.

Chronic Myeloid Leukemia (CML)

Myeloproliferative neoplasm driven by the BCR::ABL1 fusion (Philadelphia chromosome) producing marked leukocytosis and basophilia.

Chronic Lymphocytic Leukemia (CLL)

Indolent B-cell leukemia/lymphoma with CD5+, CD23+ small lymphocytes and smudge cells; most common adult leukemia in the West.

Myeloproliferative Neoplasm (MPN)

Group of chronic clonal stem-cell disorders with overproduction of mature myeloid cells (e.g., CML, PV, ET, PMF).

Myelodysplastic Syndrome (MDS)

Clonal marrow disorder with ineffective hematopoiesis, cytopenias, and dysplasia; can progress to AML.

Therapy-related AML (t-AML)

Acute myeloid leukemia arising after chemotherapy or radiotherapy, often with complex karyotype and poor prognosis.

Auer Rod

Cytoplasmic, needle-like azurophilic inclusion in myeloblasts; pathognomonic for myeloid lineage, especially AML.

Philadelphia Chromosome

Shortened chromosome 22 resulting from t(9;22)(q34;q11) that creates the BCR::ABL1 fusion gene.

BCR::ABL1 Fusion Gene

Constitutively active tyrosine kinase produced by t(9;22); hallmark of CML and a subset of ALL.

JAK2 V617F Mutation

Gain-of-function mutation activating JAK-STAT signaling; present in nearly all PV and many ET or PMF cases.

Tyrosine Kinase Inhibitor (TKI)

Drug class (e.g., imatinib) that blocks pathologic kinase activity, especially BCR::ABL1 in CML.

Flow Cytometry

Immunophenotyping technique that detects cell-surface and cytoplasmic markers to classify leukemias.

Cytogenetic Testing

Karyotyping and FISH methods used to identify chromosomal abnormalities (e.g., t(8;21), inv(16)) in leukemias.

Myeloperoxidase (MPO) Stain

Cytochemical stain positive in myeloid blasts; differentiates AML from ALL.

Sudan Black B (SBB) Stain

Lipid stain that parallels MPO positivity, highlighting myeloid granules in AML.

Terminal Deoxynucleotidyl Transferase (TdT)

DNA polymerase expressed in immature lymphoid cells; immunostain is positive in most ALL cases.

Tartrate-Resistant Acid Phosphatase (TRAP)

Enzyme stain characteristically positive in hairy cell leukemia and helpful for its diagnosis.

Germline RUNX1 Mutation

Inherited RUNX1 alteration that predisposes to familial AML and other myeloid malignancies.

Hairy Cell Leukemia (HCL)

Rare indolent B-cell leukemia with cytoplasmic projections, TRAP positivity, and BRAF V600E mutation.

Polycythemia Vera (PV)

MPN with increased red cell mass, almost always harboring JAK2 V617F; treated with phlebotomy and cytoreduction.

Essential Thrombocythemia (ET)

MPN featuring persistent thrombocytosis due to JAK2, CALR, or MPL mutations, with thrombotic and bleeding risks.

Primary Myelofibrosis (PMF)

MPN characterized by marrow fibrosis, extramedullary hematopoiesis, tear-drop RBCs, and JAK2/CALR/MPL mutations.

Erythromelalgia

Painful, burning erythema of extremities triggered by heat or exertion; seen in PV and ET.

Down Syndrome–Associated Leukemia

Increased risk of AML (especially megakaryoblastic) and ALL in individuals with Trisomy 21.

Nonspecific Esterase (NSE) Stain

Cytochemical stain highlighting monocytic differentiation; positive in AML-M4/M5, negative in most ALL.

Basophilia

Elevated basophil count in peripheral blood; commonly associated with CML and other MPNs.