Case 3: B-lymphoblastic leukemia/lymphoma
Clinical Vignette
This 4-year-old male presents with pancytopenia. A bone marrow sample is submitted for flow cytometric immunophenotyping using ClearLLab 10C Panels.
Flow Cytometric Immunophenotyping
B Cell Tube
Figure B04. This CD45 vs Side Scatter dot plot shows events in the Cells gate. This plot is intended to highlight various subsets of white blood cells, which are gated as CD45 positive. The CD45 negative population (Gray colored events) usually includes red blood cells, platelet aggregates, tissue debris or non-hematopoietic cells.
Figure B05. This CD45 vs Side Scatter dot plot shows events in the CD45+ gate. This dot plot permits distinction of several white blood cell populations typically found in peripheral blood, bone marrow, and lymph node samples, including lymphocytes (Gate Ly, red/orange), monocytes (Gate Mo, green), and granulocytes (Gate Gr, blue). The CD45dim gate (purple) covers the area typically occupied by early progenitors (e.g., myeloblasts and immature B cells). Basophils, plasmacytoid dendritic cells, plasma cells and NK cells may also appear in this area. By applying different colors to the events comprised by each gate, the various populations may be followed throughout the analysis. The progenitor population in the CD45dim gate (purple) is expanded.
Figure B06. This CD19 vs Side Scatter dot plot shows events in the Cells gate. The CD19+ gate identifies CD19 positive cells (orange). CD19 is expressed on mature and immature B cells, as well as most plasma cells. These cells typically have low to moderate side scatter. The aberrant population (purple) has variably increased side scatter and expresses CD19.
Figure B09. This CD10 vs Side Scatter dot plot shows all viable cells. CD10 is expressed on immature B cells, mature germinal center B cells, and mature granulocytes (blue). The granulocytes have high side scatter, in contrast to lymphoid cells that have low side scatter. The aberrant population (purple) expresses CD10.
Figure B11. This CD200 vs Side Scatter dot plot shows all viable cells. CD200 is typically expressed on B cells, but is negative in some neoplastic B cells. It is especially useful in distinguishing mantle cell lymphoma (usually CD200 negative) from chronic lymphocytic leukemia/small lymphocytic lymphoma (usually CD200 positive). The aberrant population (purple) expresses CD200.
Figure B12. This CD34 vs Side Scatter dot plot shows all viable cells. CD34 is a marker of early hematopoietic progenitors. It is expressed on hematopoietic stem cells, early myeloid progenitors (myeloblasts), and immature B and T cells (lymphoblasts). The aberrant population (purple) expresses CD34 on a subset.
Figure B13. This CD38 vs Side Scatter dot plot shows all viable cells. CD38 is an activation marker. It is expressed at the highest level on plasma cells, at a moderate level on immature myeloid and lymphoid progenitors, at a low level on monocytes, and at a variable level on activated mature lymphocytes (red/orange). The aberrant population (purple) has intermediate CD38 expression.
Figure B16. This CD10 vs CD38 dot plot shows the aberrant population in the CD45dim gate. The aberrant population (purple) displays uniform CD10 and CD38 expression.
Flow Cytometry Result Interpretation
Flow cytometric immunophenotyping identifies a phenotypically distinct population of cells that express bright CD10, dim CD13, intermediate CD19, variable CD20, dim CD33, CD34 (subset), intermediate CD38, dim CD45, intermediate CD123, bright CD200, and bright HLA-DR without significant expression of other T cell or myeloid markers. Compared with normal B cell precursors, the expression of increased CD10, dim CD13, dim CD33, CD34 on a subset, and CD123 are aberrant.
Taken together, the findings in this case are most consistent with B-lymphoblastic leukemia/lymphoma. Note that correlation with clinical and laboratory data is recommended, and that additional immunophenotyping may be warranted.