SCYM Immunophenotyping 4 — Questions and Answers
Question 1: In immunophenotyping for minimal residual disease (MRD) in B-ALL, which combination is most commonly used to identify residual leukemic B-lymphoblasts?
- CD19+/CD10+/TdT+/CD34+ with aberrant markers (Correct answer)
- CD20+/CD5+/CD23+ with dim sIg
- CD38+/CD138+/CD56+ lacking CD19
- CD3+/CD4+/CD8+ with high TdT
Correct answer: CD19+/CD10+/TdT+/CD34+ with aberrant markers
MRD detection in B-ALL relies on identifying CD19+/CD10+/TdT+/CD34+ B-lymphoblasts with leukemia-associated aberrant phenotypes that distinguish them from normal hematogones.
Question 2: Which immunophenotypic feature distinguishes hematogones (normal B-cell precursors) from leukemic B-lymphoblasts in MRD assessment?
- Hematogones show a continuum of CD19/CD10 maturation stages (Correct answer)
- Hematogones express bright CD34 at all stages
- Hematogones lack TdT expression entirely
- Hematogones express aberrant CD33 or CD13
Correct answer: Hematogones show a continuum of CD19/CD10 maturation stages
Normal hematogones display a characteristic maturation spectrum with progressive brightening of CD19 and dimming of CD10, while leukemic blasts cluster as a discrete, phenotypically homogeneous population.
Question 3: In the immunophenotyping of large granular lymphocyte (LGL) leukemia, which phenotype indicates a T-LGL versus NK-LGL proliferation?
- CD3+/CD8+/CD57+ (T-LGL) vs CD3-/CD16+/CD56+ (NK-LGL) (Correct answer)
- CD4+/CD25+/FOXP3+ vs CD3-/CD19+
- CD5+/CD23+ vs CD103+/CD11c+
- TdT+/CD34+ vs CD38+/CD138+
Correct answer: CD3+/CD8+/CD57+ (T-LGL) vs CD3-/CD16+/CD56+ (NK-LGL)
T-LGL leukemia shows CD3+/CD8+/CD57+ cytotoxic T cells, while NK-LGL leukemia presents with CD3-/CD16+/CD56+ NK cells, distinguished primarily by the presence or absence of CD3.
Question 4: Which flow cytometric finding is most consistent with systemic mastocytosis when evaluating mast cells in a bone marrow sample?
- CD117+/CD25+ co-expression on mast cells (Correct answer)
- CD34+/HLA-DR+ mast cell precursors
- CD3+/CD4+ mast cells with CD117
- CD20+/CD10+ mast cells without CD25
Correct answer: CD117+/CD25+ co-expression on mast cells
Aberrant CD25 co-expression on CD117+ mast cells is a key diagnostic criterion for systemic mastocytosis, reflecting KIT D816V-driven abnormal activation.
Question 5: When using flow cytometry for lymphocyte subset enumeration in HIV monitoring, which absolute count is clinically most critical?
- Absolute CD4+ T-cell count per microliter (Correct answer)
- Total CD3+ T-cell count
- CD19+ B-cell percentage
- NK cell absolute count
Correct answer: Absolute CD4+ T-cell count per microliter
The absolute CD4+ T-cell count is the primary immunological parameter used to stage HIV disease, guide antiretroviral therapy initiation, and assess prophylaxis needs.
Question 6: Which immunophenotypic feature is most helpful in distinguishing diffuse large B-cell lymphoma (DLBCL) of germinal center (GCB) versus activated B-cell (ABC) subtype by flow cytometry?
- CD10 expression (GCB) versus its absence (ABC) (Correct answer)
- CD5 co-expression in GCB only
- TdT positivity in ABC subtype
- CD14 expression in GCB subtype
Correct answer: CD10 expression (GCB) versus its absence (ABC)
CD10 expression correlates with germinal center B-cell origin and is used as a surrogate flow cytometric marker to approximate the GCB subtype of DLBCL.
Question 7: In immunophenotyping of myelodysplastic syndrome (MDS), which flow cytometric abnormality on granulocyte precursors is most diagnostically informative?
- Asynchronous CD16/CD13 maturation pattern (Correct answer)
- Absent HLA-DR on myeloid blasts
- CD19 expression on granulocytes
- Bright CD45 on immature myeloid cells
Correct answer: Asynchronous CD16/CD13 maturation pattern
In MDS, granulocytic maturation shows an abnormal CD13 vs CD16 pattern with loss of the normal parabola shape, reflecting dysplastic maturation.
SCYM Immunophenotyping 4
In immunophenotyping for minimal residual disease (MRD) in B-ALL, which combination is most commonly used to identify residual leukemic B-lymphoblasts?