Deciphering stage 0 hematogones by flow cytometry in follow-up bone marrow samples of pediatric B-Acute lymphoblastic leukemia cases: A potential mimicker of residual disease after anti CD19 therapy

CD19 is frequently targeted for immunotherapy in B cell malignancies, which may result in loss of CD19 expression in leukemic cells as an escape mechanism. Stage 0 hematogones (Hgs) are normal CD19-negative very early B cell precursors that can be potentially mistaken for CD19 negative residual leukemic cells by flow cytometry (FCM) in B cell acute lymphoblastic leukemia (BCP-ALL) cases treated with anti CD19 therapy. Our main objective was to characterize and study the incidence of stage 0 hematogones in follow-up bone marrow samples of pediatric BCP-ALL cases. We analyzed the flow cytometry standard files of 61 pediatric BCP-ALL cases treated with conventional chemotherapy and targeted anti-CD19 therapy, for identifying the residual disease and normal B cell precursors including stage 0 Hgs. A non-CD19 alternate gating strategy was used to isolate the B cells for detecting the residual disease and stage 0 Hgs. The stage 0 Hgs were seen in 95% of marrow samples containing CD19+ Hgs. When compared with controls and posttransplant marrow samples, the fraction of stage 0 Hgs was higher in patients receiving anti CD19 therapy (p = 0.0048), but it was not significant when compared with patients receiving chemotherapy (p = 0.1788). Isolated stage 0 Hgs are found in samples treated with anti-CD19 therapy simulating CD19 negative residual illness. Our findings aid in understanding the stage 0 Hgs and its association with CD19+ Hgs in anti CD19 therapy and conventional chemotherapy. This is crucial as it can be potentially mistaken for residual disease in patients treated with anti CD19 therapy.

Prognostic Value of Hematogones in Patients With Hematopoietic Disorders After Allogeneic Hematopoietic Stem Cell Transplantation: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis aimed to determine whether hematogones in patients with hematopoietic disorders after allogeneic hematopoietic stem cell transplantation (allo-HSCT) are associated with clinical outcomes. We searched the MEDLINE, Embase, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, and World Health Organization International Clinical Trials Registry Platform databases from their inception to March 2023. The primary outcome in the summary of findings was three-year relapse-free survival (RFS), and secondary outcomes in the summary of findings included three-year relapse, non-relapse mortality (NRM), overall survival (OS), acute and chronic graft-versus-host disease (GVHD), and infection. The certainty of evidence was determined using the grading of recommendation assessment, development, and evaluation approaches. A systematic review and meta-analysis of outcome measures were conducted using a random-effects model. This study protocol was registered in the Open Science Framework. A total of six studies (including 888 patients) were included in the meta-analysis. Hematogones were related to favorable three-year RFS (risk ratio (RR) = 1.84; 95% confidence interval (CI) = 1.01 to 3.34) and favorable NRM (RR = 0.14; 95% CI = 0.04 to 0.51), OS (RR = 1.51; 95% CI = 1.13 to 2.02), and acute GVHD (RR = 0.44; 95% CI = 0.33 to 0.59). The certainty of the evidence was low for RFS, NRM, OS, and acute GVHD. Evidence regarding the association between hematogones, relapse, and infections is uncertain. Hematogones may be a prognostic factor for long-term prognosis and acute adverse events in patients with hematopoietic disorders after allo-HSCT. Further studies are required to address the long-term life-threatening events.

The prognostic significance of hematogones in childhood B-cell acute lymphoblastic leukemia

BACKGROUND

Recent studies have demonstrated hematogones (HGs) expansion to be associated with favorable outcomes in hematological diseases, especially in patients with acute myeloid leukemia and patients undergoing hematopoietic stem cell transplantation. Acute lymphoblastic leukemia (ALL) is the most common form of cancer in children. As of now, minimal residual disease (MRD) remains the most compelling independent prognostic factor in childhood ALL. There is need for more prognostic tools for evaluating relapse risk.

PROCEDURE

The goal of this study was to assess the prognostic value of HGs on relapse-free survival (RFS) and overall survival (OS) in childhood ALL. In this prospective cohort study, a total of 122 subjects with definitive diagnosis of precursor B lymphoblastic leukemia were evaluated. Flow cytometric HG detection was performed in bone marrow aspirates after induction and consolidation therapy.

RESULTS

The median follow-up period of patients was 35.5 ± 9.4 (SD) months. Patients who had at least 1.0% HGs had a significantly better RFS (p = .023). Moreover, univariate and multivariate analyses confirmed that positive HGs were independently associated with longer RFS (unadjusted model: hazard ratio = 0.33, 95% CI = 0.12-0.91, p = .031; adjusted model: hazard ratio = 0.30, 95% CI = 0.11-0.82, p = .020).

CONCLUSIONS

Along with the role of MRD, our study shows the significance of HGs as an independent prognostic factor. The results indicate the independent prognostic value of HGs on RFS after adjustment for other prognostic factors, and can be beneficial for risk stratification and treatment modifications amongst pediatric B-cell ALL patients.

Easy discrimination of hematogones from lymphoblasts in B-cell progenitor acute lymphoblastic leukemia patients using CD81/CD58 expression ratio

INTRODUCTION

The discrimination of leukemia lymphoblasts (LB) in diagnosis and follow-up of B-cell progenitor acute lymphoblastic leukemia (BCP-ALL) by multiparameter flow cytometry (MFC) may be difficult due to the presence of hematogones (HG). The aim of this study was to compare lymphoblasts of BCP-ALL and HG for the expression of the most discriminating antigens.

METHODS

A total of 82 bone marrow samples (39 BCP-ALL and 43 patients with HG) were analyzed using MFC. Mean fluorescence intensity (MFI) was measured for ten markers commonly used in hematology laboratories: CD45, CD19, CD10, CD34, CD38, CD20, CD22, CD58, CD81, and CD123. Statistical comparison of the MFI between LB and HG was performed. The presence on LB of aberrant expression of myeloid and/or T-cell markers was also investigated.

RESULTS

Qualitative pattern expression of antigens showed overexpression on LB of CD58, CD22, CD34, CD10 and underexpression of CD81, CD45, CD38 when compared to HG. Expression of CD123 was positive in 34% of BCP-ALL LB and always absent on HG. Aberrant antigen expression (myeloid and/or T-cell marker) including CD123 was observed in 58% of BCP-ALL patients. The use of a MFI antigen ratio of the most discriminating markers (CD81/CD58) (analysis of variance, P < 0.005) increased the distinction of LB versus HG with a high specificity and sensitivity as demonstrated by the use of ROC curve analysis (AUC of CD81/CD58: 0.995).

CONCLUSION

We demonstrate in this study that routine use of the MFI antigen ratio (CD81/CD58) in addition to the MFC evaluation using WHO classical criteria appears to be an efficient approach to discriminate LB from HG.

Quantification of marrow hematogones following autologous stem cell transplant in adult patients with plasma cell myeloma or diffuse large B-cell lymphoma and correlation with outcome

In this retrospective study, we quantified the hematogone (normal B-lineage precursor) population by flow cytometric immunophenotyping in post-transplant bone marrow biopsy specimens from adult patients who received an autologous stem cell transplant for either plasma cell myeloma (n = 57) or diffuse large B-cell lymphoma (n = 73). The majority of patients (80%) had <5% marrow hematogones post-transplant. Extreme (>10%) hematogone percentages were quite rare, seen in only four patients, and were not associated with disease progression. There was a positive association between the post-transplant day and hematogone percentage within the first year after transplant, and a negative association thereafter. Plasma cell myeloma patients with ≥5% hematogones in any post-transplant flow cytometry study had a worse overall survival as did plasma cell myeloma patients with increased hematogones (as defined by percentile) at 100 days post-transplant. These findings require further study, ideally in a prospective study design.

Hematogones Detected by Flow Cytometry in a Child with Vitamin B12 Deficiency

Vitamin B12 deficiency is a known cause of megaloblastic anemia and bone marrow failure. Bone marrow biopsies are not frequently performed as part of the diagnostic workup and can demonstrate morphologic features that overlap with myelodysplastic syndrome (MDS) and acute leukemia. We describe a case of a dysplastic bone marrow with increased bone marrow hematogones detected by flow cytometry in a child with vitamin B12 deficiency. Hematogones are normal B cell precursors, and hyperplasia has been described in a variety of often reactive conditions and also disease. Hematogones are not typically seen in MDS. The presence of hematogones may help differentiate the dysplastic changes seen in vitamin B12 deficiency from MDS.

Hematogones With Lambda Light Chain Restriction in a 4-Year-Old Boy With Burkitt Lymphoma: A Potential Diagnostic Pitfall

Hematogones are immature normal B cell precursors with a characteristic immunophenotype profile on flow cytometry that typically do not express surface immunoglobulin light chains. In this report, we describe a case in which the hematogones exhibit light chain restriction. Our patient was a 4-year-old boy with a complicated medical history involving treatment for a presumed bilateral Wilms tumor of the kidney that on later resection was diagnosed as Burkitt lymphoma. Flow cytometry analysis of his bone marrow revealed a small distinct population of cells expressing dim cluster of differentiation (CD)10, CD19, CD22, CD38, dim CD58, human leukocyte antigen-D related (HLA-DR), and dim CD45, which are characteristic of hematogones. These cells, however, demonstrated dim surface immunoglobulin lambda light-chain restriction. Molecular study results for immunoglobulin heavy and kappa light-chain gene rearrangements were negative. We present this case to raise awareness of the potential pitfalls of working up bone marrow for involvement by B cell lymphoproliferative disorder.

Hematogones: a sensitive prognostic factor for Chinese adult patients with acute myeloid leukemia

BACKGROUND

Hematogones (hgs) are normal B-lymphocyte precursors that increase in some hematologic diseases. Many studies indicate that hgs might be a favourable prognostic factor. We thus considered it important to determine whether hgs are also a prognostic factor for Chinese adult patients with acute myeloid leukemia (aml) and whether the hg-positive and hg-negative groups show any serologic or phenotypic differences.

METHODS

Chinese adult aml patients (n = 177) who were all initially hg-negative underwent standard chemotherapy and were thereafter divided into hg-positive and hg-negative groups according to hg levels in bone marrow during their first remission.

RESULTS

The follow-up study confirmed that survival duration (both leukemia-free and overall) was significantly greater in the hg-positive group than in the hg-negative group and was accompanied by a lower relapse rate. A retrospective study of patient characteristics at the time of first diagnosis revealed some differences between the hg-positive and the hg-negative groups, including elevations in white blood cells, lactate dehydrogenase, and β2-microglobulin in the hg-negative group. Retrospective phenotypic analysis revealed a significantly lower proportion of abnormal chromosome karyotype and CD34 expression in hg-positive patients. Finally, we evaluated whether additional intensive chemotherapy after standard chemotherapy could further increase hgs.

CONCLUSIONS

The present work verified the validity of hgs as a prognostic factor for Chinese adult patients with aml. Compared with hg-negative patients, hg-positive patients not only experienced longer survival and a lower relapse rate, but they also had some serologic and phenotypic characteristics that are all considered indicators of better outcome. Additional intensive chemotherapy could further increase the level of hgs, which might imply better clinical results.

Bone marrow infiltration of CD20-negative follicular lymphoma after rituximab therapy: a histological mimicker of hematogones and B-cell acute lymphoblastic leukemia/lymphoma

Rituximab is a monoclonal antibody against CD20. Rituximab combined with CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy, termed R-CHOP, have improved the overall survival of patients with B-cell lymphoma in comparison with that of CHOP therapy. However, as with other molecularly-targeted therapies, resistance to rituximab could emerge sooner or later after rituximab administration. A number of mechanisms for rituximab resistance have been proposed, including downregulation of CD20 protein expression. Differential diagnosis of B-cell proliferation with reduced or lost CD20 expression includes not only B-cell lymphomas with CD20 downregulation, but also other tumorous and non-tumorous lesions. These include precursor B-cell neoplasms such as B acute lymphoblastic leukemia/lymphoblastic lymphoma (B-ALL/LBL) and hematogones, a normal precursor B-cell proliferation during regeneration of hematopoiesis, typically observed following bone marrow suppression by chemotherapy. It is important to distinguish these possibilities because distinct therapies are required for each. In this paper, we report a case where bone marrow infiltration of follicular lymphoma histopathologically mimicked hematogones or B-ALL/LBL when CD20 expression was downregulated in follicular lymphoma after R-CHOP therapy.

Hematogones in the peripheral blood of a 5½-month-old boy with cyclic neutropenia due to heterozygous, novel ELANE gene mutation p.Q97P, c.290 A>C

We have identified a novel point mutation in the ELANE gene of a 5.5-month-old boy with severe cyclic neutropenia, and we are reporting for the first time, to our knowledge, the presence of hematogones in the peripheral blood of an infant. The novel point mutation occurred at base number 290 in codon 97, where adenine was replaced with cytosine. The mutation caused the replacement of amino acid glutamine with amino acid proline in the activation domain of the elastase 2 enzyme. The heterozygous mutation generated severe cyclic neutropenia, granulocytic maturation arrest, an increased number of hematogones (26% of marrow cells) in the bone marrow, an absence of neutrophils, and the presence of stage 3 (mature) hematogones in the peripheral blood. The percentage of hematogones in the peripheral blood was inversely proportional to the absolute number of neutrophils. Leukemic number of blast-like cells (hematogones) in the bone marrow, blast-like cells in the peripheral blood, marked neutropenia, and the arrest of granulopoiesis might suggest an acute leukemia. However, the finding of characteristic flow cytometric features of hematogones should help to avoid a wrong diagnosis.

Multiparameter Flow Cytometry to Detect Hematogones and to Assess B-lymphocyte clonality in Bone Marrow Samples from Patients with Non-Hodgkin Lymphomas

Hematogones are precursors of B-lymphocytes detected in small numbers in the bone marrow. Flow cytometry is the most useful tool to identify hematogones and, so far, 4-color methods have been published. In addition, flow cytometry is used in the diagnosis and follow-up of lymphomas. We developed a flow cytometric 7-color method to enumerate hematogones and to assess B-lymphocyte clonality for routine purposes. We evaluated 171 cases of B-cell non-Hodgkin lymphomas, either at diagnosis or in the course of follow-up. By our diagnostic method, which was carried out by the combination K/λ/CD20/CD19/CD10/CD45/CD5, we were able to detect hematogones in 97.6% of samples and to distinguish normal B-lymphocytes, neoplastic lymphocytes and hematogones in a single step. The percentage of hematogones showed a significant inverse correlation with the degree of neoplastic infiltration and, when bone marrow samples not involved by disease were taken into consideration, resulted higher in patients during follow-up than in patients evaluated at diagnosis.

Analysis of hematogones in bone marrow from acute myeloid leukaemia cases posttherapy

BACKGROUND

Increased bone marrow (BM) hematogones (HGs) are often observed in patients with marrow regenerating status. Many studies have focused on the role of HGs in acute lymphoblastic leukaemia (ALL), but very little has been done to understand their effects on acute myeloid leukaemia (AML).

MATERIALS AND METHODS

Through immunophenotyping, HGs were quantified in 471 BM samples from 292 postchemotherapy AML cases. These samples were analysed to determine whether there is any relationship between HGs percentages and French-American-British (FAB) subtypes or risk stratification of AML.

RESULTS

HGs were identified in 57.75% of 471 patient samples (271) with a mean percentage of 3.87 ± 0.25%. No significant differences were found amongst different FAB subtypes of AML (P > 0.05). However, significant differences (P < 0.05) in HG numbers were noted between AML patients experiencing haematological complete remission (HCR) and those who have relapsed. HGs were identified in 59.9% of samples under HCR with a mean per cent of 3.98 ± 0.31%, and 36.7% of individuals who have relapsed have detectable HGs with a mean per cent of 1.75 ± 0.47. In addition, HGs in patients groups with low risk or intermediate risk were elevated when compared with high-risk groups (P < 0.05), whilst no significant difference was found between low-risk patients and intermediate-risk patients (P > 0.05). Patients with >0.1% of HGs had a significantly better median leukaemia-free survival (LFS) and overall survival (OS) than those with <0.1% of HGs (P < 0.01).

CONCLUSIONS

Therefore, our data indicate that HGs in bone marrow may be used as a favourable prognostic factor that predict for a better outcome of AML patients.

Impact of bone marrow hematogones on umbilical cord blood transplantation outcomes in patients with acute myeloid leukemia

Early after umbilical cord blood transplantation, patients show marked differences in bone marrow (BM) hematogone percentages. Little is known about whether these differences are clinically relevant. We hypothesized that early recovery of hematogones may be associated with improved transplantation outcomes. BM aspirates were assessed from 88 patients with acute myeloid leukemia by two independent reviewers at day 21 and 100 after umbilical cord blood transplantation. Interobserver variability for BM hematogone percentages at these time points showed correlation coefficients of 0.83 and 0.98, respectively (P ≤ .01 for both). A high percentage of hematogones at day 21 was associated with less acute graft-versus-host disease grade 3 to 4 (P = .01). At day 100, a high percentage of BM hematogones was associated with improved overall survival (P = .02) and lower treatment-related mortality (P ≤ .01). This study shows that BM hematogone percentages may be useful prognostic indicators in patients with acute myeloid leukemia after umbilical cord blood transplantation and should be routinely reported in BM differential counts.

Development of acute lympboblastic leukemia in a patient with increased hematogones after toxic bone marrow damage

To the best of our knowledge we describe the first case showing the association of increased B cell precursors/hematogones in a regenerating post-toxic bone marrow with subsequent development of a B-ALL. Since all immunohistochemical/moleculargenetic anaylses have failed to identify the initial malignant leukemic clone, we suggest a close-meshed follow-up of such cases to identify potential mechanisms for the malignant transformation of B-cell precursors/hematogones and to prevent further fatal courses.

The presence of precursors of benign pre-B lymphoblasts (hematogones) in the bone marrow of a paediatric patient with cytomegalovirus infection

Hematogones are normal B-lymphoid precursors that multiply in the bone marrow of small children and of adults with ferropenic anaemia, neuroblastoma or idiopathic thrombocytopenic purpura. They are not normally found in peripheral blood, and the immunophenotype is virtually indistinguishable from that of B lymphoblasts. We discuss the case of a 3-month infant with an active cytomegalovirus infection, with hepatitis and pancytopenia associated with 13% hematogones in the bone marrow.