PMC9050327_01
Peripheral blood smears (Wright-Giemsa stained) showing dimorphic lymphoid population at low magnification ((a), 400x) with a lymphoblast (arrow), two atypical small mature lymphocytes, and a band. (b) Lymphoblasts at higher magnification (1000x). Flow cytometric analysis of peripheral blood demonstrating B acute lymphoblastic leukemia with blasts coexpressing CD34 and TdT (c) and cocirculating monoclonal B cell lymphocytosis with aberrant coexpression of CD5 and CD23 (d).
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fig1
PB smear review showed mild polychromasia, mild left shift (few myelocytes), few nucleated red blood cells, and atypical lymphocytosis comprised of two morphologically distinct populations (Figure 1). However, a few undifferentiated blasts with fine chromatin, high nuclear: cytoplasmic ratio, and prominent nucleoli were also noted, concerning for high-grade hematopoietic malignancy (Figure 1). Flow cytometry (FC) analysis using standard CD45 vs. side scatter gating (Figure 1) revealed approximately 17% lymphoblasts positive for CD19, CD22, CD10, CD34, HLA-DR, and TdT and negative for CD20, CD5, CD23, CD25, CD103, CD11c, CD36, CD56, MPO, CD13, CD33, and CD14, compatible with evolving B-ALL.
Bone marrow sections (hematoxylin and eosin stained) with sheets of lymphoblasts ((a), 100x). Heterogeneous lymphoblasts in bone marrow aspirates (Wright-Giemsa stained) at high magnification ((b), 1000x). Immunohistochemistry demonstrating positivity for TdT (c) and CD34 (d) on lymphoblasts in bone marrow sections (100x).
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fig2
B cells (positive for CD19, CD20, CD5, CD23, CD25, and CD11c and negative for CD38, CD10, CD34, CD103, CD56, and FMC7), immunophenotypically consistent with CLL but at the level of monoclonal B cell lymphocytosis/monoclonal B cell lymphocytosis of uncertain significance (MBL/MLUS). Bone marrow (BM) examination confirmed the diagnosis of precursor B-ALL with approximately 76% lymphoblasts (Figure 2).
DNA isolated from the bone marrow aspirate and peripheral blood was analyzed for clonal rearrangements of the immunoglobulin heavy chain gene using the BIOMED-2 primer sets in the IGH Gene Clonality Assay Kit (InVivoScribe). Three PCR reactions were carried out with upstream primers in the FR1, FR2, and FR3 regions of the IGH gene and a downstream primer in the JH region. The images show results with the FR2-JH primer set.
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fig3
This assay yielded five distinct PCR products with the FR1 and FR2 primer sets and four with FR3 (Figure 3).