SCYM Clinical Applications 5 â Questions and Answers
Question 1: In the WHO classification of acute leukemias, what percentage of blasts in bone marrow defines AML (in the absence of recurrent genetic abnormalities)?
- â„20% (Correct answer)
- â„10%
- â„30%
- â„5%
Correct answer: â„20%
The WHO 2022 classification requires â„20% blasts in bone marrow or peripheral blood to diagnose AML without a defining genetic abnormality.
Question 2: Which flow cytometric parameter is most useful for distinguishing reactive plasmacytosis from myeloma plasma cells?
- Aberrant CD19 loss with CD56 gain and Îș/λ light chain restriction (Correct answer)
- Increased absolute plasma cell count only
- CD138 expression intensity
- CD38 fluorescence brightness alone
Correct answer: Aberrant CD19 loss with CD56 gain and Îș/λ light chain restriction
Myeloma plasma cells typically lose CD19, gain CD56, and show monoclonal light chain restriction, whereas reactive plasma cells are CD19+/CD56-/polyclonal.
Question 3: In the diagnosis of chronic myelomonocytic leukemia (CMML), which flow cytometric finding supports the diagnosis?
- Expansion of CD14+/CD16- classical monocytes exceeding 94% of monocytes (Correct answer)
- Increased CD34+ blasts above 20% of marrow cells
- Monoclonal B-cell population with CD5 expression
- Absence of CD33 on all myeloid cells
Correct answer: Expansion of CD14+/CD16- classical monocytes exceeding 94% of monocytes
CMML is associated with accumulation of classical CD14+/CD16- monocytes comprising â„94% of circulating monocytes by flow cytometry.
Question 4: Which cytometric approach is used to identify circulating endothelial cells (CECs) as a biomarker of vascular damage?
- CD146+/CD105+/CD45-/CD31+ cells in peripheral blood (Correct answer)
- CD34+/CD133+/CD45- progenitor cells
- CD62E+/CD54+/CD45+ cells
- CD31+/CD41+/CD45- platelet-derived microvesicles
Correct answer: CD146+/CD105+/CD45-/CD31+ cells in peripheral blood
CECs are identified as CD146+, CD105+, CD31+ cells that are CD45-negative to distinguish them from hematopoietic cells.
Question 5: For detecting antigen-specific T cells (e.g., viral or tumor-specific), which flow cytometry tool uses MHC-peptide complexes to directly stain T cells?
- Peptide-MHC tetramers (Correct answer)
- Intracellular cytokine staining after PMA stimulation
- ELISPOT with fluorescent antibodies
- Proliferation dye dilution assay
Correct answer: Peptide-MHC tetramers
Peptide-MHC tetramers directly bind the T-cell receptor of antigen-specific T cells, enabling their identification without requiring activation.
Question 6: When evaluating primary hemophagocytic lymphohistiocytosis (HLH) by flow cytometry, which functional assay is most relevant?
- NK cell degranulation assay measuring CD107a surface mobilization (Correct answer)
- CD4+ T-cell cytokine production by intracellular staining
- B-cell proliferation response to mitogen
- Neutrophil oxidative burst by DHR assay
Correct answer: NK cell degranulation assay measuring CD107a surface mobilization
Primary HLH involves defective cytotoxic granule exocytosis; NK cell degranulation is measured by CD107a (LAMP-1) upregulation after target cell stimulation.
Question 7: In flow cytometric immunophenotyping of mantle cell lymphoma (MCL), which marker distinguishes it from CLL?
- Cyclin D1 overexpression and CD23 negativity (Correct answer)
- CD23 positivity and dim CD20
- CD10 positivity and CD5 negativity
- CD38 bright expression and CD19 negativity
Correct answer: Cyclin D1 overexpression and CD23 negativity
MCL is CD5+/CD23- and overexpresses cyclin D1 due to t(11;14), whereas CLL is CD5+/CD23+ and cyclin D1-negative.
SCYM Clinical Applications 5
In the WHO classification of acute leukemias, what percentage of blasts in bone marrow defines AML (in the absence of recurrent genetic abnormalities)?