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Objectives: To improve diagnostic accuracy in differentiating hematogones from leukemic blasts in cases of precursor B-lymphoblastic leukemia/lymphoma (B-ALL), particularly those that are posttreatment or after bone marrow transplant, and to provide an algorithmic approach to this diagnostic challenge., Methods: A seven-color antibody panel including CD10, CD19, CD45, CD38, CD34, CD58, and CD81 was generated to assess the feasibility of a single tube panel and provide an algorithmic approach to distinguish hematogones from B-ALL. Fifty-three cases were analyzed, and results were correlated with histology and ancillary studies., Results: There was a significant difference in mean fluorescent intensity (MFI) for CD81 and CD58 when comparing hematogones and B-ALL populations (P < .001). B-ALL cases had a mean (SD) MFI of 24.6 (27.5; range, 2-125) for CD81 and 135.6 (72.6; range, 48-328) for CD58. Hematogones cases had a mean (SD) MFI of 70.2 (19.2; range, 42-123) for CD81 and 38.8 (9.4; range, 23-58) for CD58., Conclusions: The flow cytometry panel with the above markers and utilization of the proposed algorithmic approach provide differentiation of hematogones from B-ALL. This includes rare cases of hematogones and B-ALL overlap where additional ancillary studies are necessary., (© American Society for Clinical Pathology, 2020. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Abstract Myeloperoxidase (MPO) is the most specific marker of the myeloid lineage, essential for diagnosing acute myeloid leukemia and mixed phenotype acute leukemia with myeloid components. In this regard, we present a unique case of B‐acute lymphoblastic leukemia (B‐ALL) with isolated MPO expression in bone marrow blasts detected by flow cytometry and immunohistochemistry, while peripheral blood blasts were negative for MPO expression. In this report, our discussion encompasses diagnostic pitfalls from a laboratory testing perspective in similar cases and includes a literature review. Furthermore, we emphasize the necessity of conducting a comprehensive analysis for the accurate diagnosis of MPO‐positive B‐ALL cases.

Objectives: New B-cell markers are needed for monitoring B lymphoblastic leukemia (B-ALL) in the era of immunotherapies directed against CD19 and CD22. The expression of leukocyte immunoglobulin-like receptor subfamily B member 1 (LILRB1) on hematogones in bone marrow (BM) and neoplastic B lymphoblasts has not yet been systematically investigated.Methods: We assessed LILRB1 expression pattern on B cells in 19 control BMs and 22 B-ALL cases by flow cytometry.Results: In all cases, mature B cells and hematogones exhibited a consistent pattern of LILRB1 expression with variable intensity over different stages of maturation, including a characteristic V-shaped pattern on hematogones. While neoplastic B lymphoblasts in all cases expressed LILRB1, the pattern of expression was distinctly abnormal relative to hematogones (loss of the dynamic pattern in all cases and abnormal expression levels in 83% of cases).Conclusions: LILRB1 is a novel diagnostic B-cell marker to aid in distinguishing neoplastic B lymphoblasts from hematogones. [ABSTRACT FROM AUTHOR]

Introduction: Minimal residual disease (MRD) is a cornerstone for stratification of upfront B‐lymphoblastic leukemia (B‐ALL) treatment protocols to decrease relapse risk. Although its detection by flow cytometry (FC) and real‐time quantitative polymerase has clinical usefulness, evidence suggests that methods with increased sensitivity could lead to improved outcomes. The aim of this study was to develop an amplicon‐based assay followed by high‐throughput sequencing of the immunoglobulin heavy chain variable region for MRD detection in B‐ALL. Methods: We analyzed 84 samples, 27 from diagnosis, 5 from relapse, 40 from post‐treatment samples, and 12 from healthy controls. Results: Our assay was able to identify more neoplastic clones at diagnosis than Sanger sequencing including incomplete DJ rearrangements. From the 40 MRD samples evaluated 21 were positive by our new approach on high‐throughput sequencing assay, but only 15 of these were positive by FC. The remaining 19 were negative by the two techniques. Conclusion: We have developed a novel approach on high‐sensitive assay for MRD detection in B‐ALL, which could add clinical value in the management of patients, especially in cases negative for MRD by FC. [ABSTRACT FROM AUTHOR]

Objectives: Autologous stem cell transplant with lenalidomide maintenance therapy has greatly improved the relapse-free and overall survival rates of patients with multiple myeloma but also has been associated with an increased risk of secondary B-lymphoblastic leukemia/lymphoma (B-ALL).Methods: We report a comprehensive review of the clinicopathologic features of 2 patients with multiple myeloma who developed secondary B-ALL during lenalidomide maintenance.Results: Our observations showed that the disease may initially present with subtle clinical, morphologic, and flow-cytometric findings. The flow cytometry findings in such cases may initially mimic an expansion of hematogones with minimal immunophenotypic variation. Both patients achieved complete remission of secondary B-ALL after standard chemotherapy; however, one patient continues to have minimal residual disease, and the other experienced relapse. Next-generation sequencing of the relapse specimen showed numerous, complex abnormalities, suggesting clonal evolution.Conclusions: Our findings suggest the need for increased awareness and further study of this unique form of secondary B-ALL. [ABSTRACT FROM AUTHOR]

Objective: To determine frequency of post induction and post consolidation minimal residual disease (MRD) in pediatric B-lymphoblastic leukemia (B-ALL) patients and its association with clinical risk factors. Methods: This is a retrospective, cross sectional study carried out at the Indus Hospital on paediatric patients (1-17 years) was performed from May 2015 to January 2018. On day 35, MRD testing was done on bone marrow aspirate using four color flow cytometer with 0.01% cut off. Positive cases were retested at post consolidation. Data was collected for demographics, total leukocyte count (TLC), central nervous system status (CNS), Cytogenetics for BCR-ABL, MLL, TEL-AML by FISH and prophase response then analyzed in association to MRD status. Results: Out of 362 patients, 133 (37%) were post induction MRD positive, with no statistically significant association to age, gender, TLC, CNS status, prophase response, BCR-ABL and TEL-AML1. However, MLL showed closely significant association (p-value=0.05). Post consolidation, 49 (44%) were MRD positive; age, National cancer institute (NCI) risk groups and CNS status showed statistical significance (p-value <0.05). Conclusion: Despite high frequency of MRD positivity, significant association is not observed between post induction MRD and risk factors. However, post consolidation MRD has a significant association with NCI risk groups, age and CNS status. [ABSTRACT FROM AUTHOR]

B-lymphoblastic leukemia/lymphoma (B-LL) is the most common childhood cancer. Circulating blasts in the peripheral blood may be rare (<1%) and missed, even when flow cytometric immunophenotyping is performed, leading to a false-negative report. The records from all patients with a new diagnosis of B-LL between January 2009 and December 2011 at our institution were reviewed. Of 130 cases with peripheral blood flow cytometry, 15 had a blast count of <1%, with 14 having electronic files for gating monocytes. The percentage of monocytes by flow cytometry and absolute monocyte counts (AMCs) were compared with peripheral blood samples that were negative by flow cytometry, sent due to cytopenia of at least 1 lineage (n 39). The monocytes from the patients with leukemia averaged 0.8% and were statistically fewer than the negative controls, which averaged 7.1% (P < 0.001). Eleven of the 14 (79%) patients with leukemia had monocytes <1%, compared to only 3 (8%) of the negative controls. The AMCs were also significantly lower (P < 0.001), with 93% of the leukemia group having an AMC <100 cells/jiL, com- pared to only 28% of the negative controls. In patients with cytopenias, percentage of monocytes may be an important diagnostic clue in determining the presence of occult leukemia. If flow cytometry is performed, acquisition of more than the standard 10 000 events is necessary to adequately assess for leukemia. If monocytes are <1% by flow cytometry in the setting of cytopenias, bone marrow examination is recommended, even with negative peripheral blood flow cytometry. [ABSTRACT FROM AUTHOR]