IGJ and SPATS2L immunohistochemistry sensitively and specifically identify BCR::ABL1+ and BCR::ABL1-like B-acute lymphoblastic leukaemia.

Therapeutic management and prognostication for patients with B-acute lymphoblastic leukaemia (B-ALL) require appropriate disease subclassification. BCR::ABL1-like B-ALL is unique in that it is defined by a gene expression profile similar to BCR::ABL1+ B-ALL rather than a unifying recurrent translocation. Current molecular/cytogenetic techniques to identify this subtype are expensive, not widely accessible, have long turnaround times and/or require an adequate liquid biopsy. We have studied a total of 118 B-ALL cases from three institutions in two laboratories to identify surrogates for BCR::ABL1+/like B-ALL. We report that immunoglobulin joining chain (IGJ) and spermatogenesis associated serine-rich 2-like (SPATS2L) immunohistochemistry (IHC) sensitively and specifically identify BCR::ABL1+/like B-ALL. IGJ IHC positivity has a sensitivity of 83%, a specificity of 95%, a positive predictive value (PPV) of 89% and a negative predictive value (NPV) of 90%. SPATS2L staining has similar sensitivity and NPV but lower specificity (85%) and PPV (70%). The presence of either IGJ or SPATS2L staining augments the sensitivity (93%) and NPV (95%). While these findings would need to be validated in larger studies, they suggest that IGJ and/or SPATS2L IHC may be utilized in identifying BCR::ABL1-like B-ALL or in selecting B-ALL cases for confirmatory molecular/genetic testing, particularly in resource-limited settings.

CLONAL DYNAMICS AND RELAPSE RISK REVEALED BY HIGH SENSITIVITY FLT3-ITD DETECTION IN ACUTE MYELOID LEUKEMIA.

The ability to detect low level disease is key to our understanding of clonal heterogeneity in acute myeloid leukemia (AML) and residual disease that elude conventional assays and seed relapse. We have developed a high sensitivity next generation sequencing (HS-NGS) clinical assay, able to reliably detect low levels (1x10-5) of FLT3-ITD, a frequent, therapeutically targetable and prognostically relevant mutation in AML. By applying this assay to 289 longitudinal samples from 62 patients at initial diagnosis and/or clinical follow up (mean follow-up of 22 months) we reveal the frequent occurrence of FLT3-ITD subclones at diagnosis and demonstrate a significantly decreased relapse risk when FLT3-ITD is cleared after induction or thereafter. We perform pairwise sequencing of diagnosis and relapse samples from 23 patients to uncover more detailed patterns of FLT3-ITD clonal evolution at relapse than is detectable by less sensitive assays. Lastly, we show that rising ITD level during consecutive biopsies is a harbinger of impending relapse. Our findings corroborate the emerging clinical utility of high sensitivity FLT3-ITD testing and expands our understanding of clonal dynamics in FLT3-ITD positive AML.

Pediatric Hodgkin Lymphoma, Version 3.2021.

Hodgkin lymphoma (HL) is a highly curable form of cancer, and current treatment regimens are focused on improving treatment efficacy while decreasing the risk of late effects of treatment. The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for pediatric HL provide recommendations on the workup, diagnostic evaluation, and treatment of classic HL, including principles of pathology, imaging, staging, systemic therapy, and radiation therapy. This portion of the NCCN Guidelines focuses on the management of pediatric classic HL in the upfront and relapsed/refractory settings.

Clonal cytopenia of undetermined significance (CCUS) with dysplasia is enriched for MDS-type molecular findings compared to CCUS without dysplasia.

OBJECTIVES: Although morphologic dysplasia is not typically considered a feature of CCUS, we have consistently observed low-level bone marrow (BM) dysplasia among CCUS patients. We sought to determine whether sub-diagnostic BM dysplasia in CCUS patients is associated with other clinico-pathologic findings of myelodysplastic syndrome (MDS). METHODS: We identified 49 CCUS patients, 25 with sub-diagnostic dysplasia (CCUS-D), and 24 having no dysplasia (CCUS-ND). We compared the clinical, histologic, and laboratory findings of CCUS-D and CCUS-ND patients to 49 MDS patients, including blood cell counts, BM morphology, flow cytometry, cytogenetics, and results of next-generation sequencing. RESULTS: No statistically significant differences were observed between CCUS-D and CCUS-ND patients in the degree of cytopenias, BM cellularity, myeloid-to-erythroid ratio, or the presence of flow cytometric abnormalities. However, compared to CCUS-ND, CCUS-D patients exhibited increased mutations in myeloid malignancy-associated genes, including non-TET2/DNMT3A/ASXL1 variants, spliceosome (SF3B1, SRSF2, ZRSR2, or U2AF1) variants, and IDH2/RUNX1/CBL variants. CCUS-D patients were also enriched for higher variant allele frequencies and co-mutation of TET2/DNMT3A/ASXL1 with other genes. CONCLUSIONS: CCUS-D patients exhibit a molecular (but not clinical) profile more similar to MDS patients than CCUS-ND, suggesting CCUS-D may represent a more immediate precursor to MDS and may warrant closer clinical follow-up.

Myeloid skewing in murine autoimmune arthritis occurs in hematopoietic stem and primitive progenitor cells.

Skewing toward myeloid cell production is often observed in chronic inflammation and autoimmune diseases. Herein, we determined whether persistent myeloid activation and proinflammatory output occurring in pathologic conditions is at the level of hematopoietic stem and primitive progenitor cells (HSPPCs). By using a mouse arthritis model, we found that even though HSPPCs in arthritis still retained the capacity to differentiate into different lineages, they acquired enhanced in vitro and in vivo propensity in a disease-dependent manner to generate myeloid cells, the key perpetrators of tissue damage in arthritis. This myeloid skewing was cell intrinsic, as arthritic HSPPCs up-regulate myeloid-specific transcripts including S100a8. Exogenous S100a8 promoted myeloid cell output from wild-type HSPPCs, suggesting mechanistic involvement of this gene in the myeloid priming that occurs in arthritic HSPPCs. Therefore, our results indicate that in arthritic mice, HSPPCs adopt a pathologic state that favors disease persistence.

Aggressive Lymphoplasmacytic Neoplasm With an Unusual In-frame Deletion of MYD88 Associated With TRAF3 and TP53 Mutations and Complex Karyotype.

Lymphoplasmacytic lymphoma often needs to be differentiated from other B-cell lymphomas with plasmacytic differentiation, especially marginal zone cell lymphoma. Molecular detection of MYD88 p.L265P hotspot mutation supports the diagnosis of lymphoplasmacytic lymphoma since it is seen in about 90% of such lymphoma, which is much higher than other B-cell lymphomas. MYD88 p.L265P is a gain-of-function mutation that enhances the activity of the NF-κB signaling pathway and therefore drives lymphomagenesis. Other mutations in MYD88 are rarely reported. This study aims to report an unusual MYD88 in-frame deletion in an aggressive lymphoplasmacytic neoplasm. This is an IgM-positive, CD5- and CD10-negative mature B-cell lymphoma with prominent plasmacytic differentiation and aggressive features. The clinical and pathologic findings were most consistent with lymphoplasmacytic lymphoma. Next-generation sequencing identified an unusual MYD88 in-frame deletion in the absence of the hotpot p.L265P mutation. Other concurrent pathogenic mutations also include truncating mutations of TRAF3, which is a negative regulator of the NF-κB signaling pathway, and a missense mutation of TP53. Karyotype analysis showed complex karyotypes, including chromosome 6q deletion. By searching literature and online cancer databases, we identified only 8 other mature B-cell lymphomas with MYD88 in-frame deletions, but none of them was diagnosed with lymphoplasmacytic lymphoma. Recognizing such in-frame deletions is necessary to help understand the mutational spectrum of MYD88 in B-cell lymphomas. It remains to be further investigated whether such MYD88 in-frame deletions are also overrepresented in lymphoplasmacytic lymphoma among other B-cell lymphomas.

Side scatter ratio of the CD105-positive and CD105-negative red blood cell fractions is useful for the detection of low-grade myelodysplastic neoplasms by flow cytometry.

OBJECTIVES: We assessed the utility of red blood cell (RBC) CD105 and side scatter (SSC) parameters by flow cytometry for the detection of low-grade myelodysplastic neoplasms (MDS) in bone marrow specimens. METHODS: Ten RBC parameters incorporating CD105 or SSC combined with the Meyerson-Alayed scoring system (MASS) metrics were retrospectively evaluated by flow cytometry for utility in detecting low-grade MDS (n = 56) compared with cytopenic controls (n = 86). RESULTS: Myelodysplastic neoplasms were associated with 7 of the RBC parameters in univariate analysis. Multivariate analysis using cutoff values based on optimal and 95% specificity levels of the RBC metrics and the MASS parameters revealed the SSC ratio of CD105-positive and CD105-negative RBC fractions (CD105+/- SSC); the percentage and coefficient of variation of the CD105-positive fraction of RBCs (CD105%, CD105+CV) emerged as significant RBC variables. Two simple scoring schemes using these RBC values along with MASS parameters were identified: 1 using CD105+/- SSC, CD105%, and CD105+CV combined with the percentage of CD177-positive granulocytes (CD177%), myeloblast percentage (CD34%), and granulocyte SSC (GranSSC), and the other incorporating CD105+/- SSC, CD105+CV, CD177%, CD34%, GranSSC, and B-cell progenitor percentage. Both demonstrated a sensitivity of approximately 80%, with a specificity of roughly 90% for the detection of MDS compared with cytopenic controls. CONCLUSIONS: The red blood cell parameter, CD105+/- SSC, appears to be beneficial in the evaluation of low-grade MDS by flow cytometry.

Infection-induced myelopoiesis during intracellular bacterial infection is critically dependent upon IFN-γ signaling.

Although microbial infections can alter steady-state hematopoiesis, the mechanisms that drive such changes are not well understood. We addressed a role for IFN-γ signaling in infection-induced bone marrow suppression and anemia in a murine model of human monocytic ehrlichiosis, an emerging tick-borne disease. Within the bone marrow of Ehrlichia muris-infected C57BL/6 mice, we observed a reduction in myeloid progenitor cells, as defined both phenotypically and functionally. Infected mice exhibited a concomitant increase in developing myeloid cells within the bone marrow, an increase in the frequency of circulating monocytes, and an increase in splenic myeloid cells. The infection-induced changes in progenitor cell phenotype were critically dependent on IFN-γ, but not IFN-α, signaling. In mice deficient in the IFN-γ signaling pathway, we observed an increase in myeloid progenitor cells and CDllb(lo)Gr1(lo) promyelocytic cells within the bone marrow, as well as reduced frequencies of mature granulocytes and monocytes. Furthermore, E. muris-infected IFN-γR-deficient mice did not exhibit anemia or an increase in circulating monocytes, and they succumbed to infection. Gene transcription studies revealed that IFN-γR-deficient CDllb(lo)Gr1(lo) promyelocytes from E. muris-infected mice exhibited significantly reduced expression of irf-1 and irf-8, both key transcription factors that regulate the differentiation of granulocytes and monocytes. Finally, using mixed bone marrow chimeric mice, we show that IFN-γ-dependent infection-induced myelopoiesis occurs via the direct effect of the cytokine on developing myeloid cells. We propose that, in addition to its many other known roles, IFN-γ acts to control infection by directly promoting the differentiation of myeloid cells that contribute to host defense.

Mucin 4 protein is expressed in B-acute lymphoblastic leukemia and is restricted to BCR::ABL1-positive and BCR::ABL-like subtypes.

Mucin 4 (MUC4) is a transmembrane mucin that, like most mucins, is not expressed in normal hematopoietic cells, but little is known about its expression in malignant hematopoiesis. B-acute lymphoblastic leukemia (B-ALL) consists of genetically distinct disease subtypes with similarities and differences in gene expression most frequently studied at the mRNA level, which is less amenable to widespread routine clinical use. Here, we demonstrate using immunohistochemistry (IHC) that MUC4 protein is expressed in less than 10% of B-ALL, with expression restricted to BCR::ABL1+ and BCR::ABL1-like (CRLF2 rearranged) subtypes of B-ALL (4/13, 31%). None (0/36, 0%) of the remaining B-ALL subtypes expressed MUC4. We compare clinical and pathologic features of MUC4+ and MUC4- BCR::ABL1+/like cases and most significantly report a possible shorter time to relapse for MUC4+ BCR::ABL1 B-ALL that would need to be validated in larger studies. In conclusion, MUC4 is a specific, albeit insensitive, marker for these high-risk subtypes of B-ALL. We propose that MUC4 IHC may be used diagnostically to rapidly identify these B-ALL subtypes, particularly in resource-limited settings or when an aspirate sample is not available for ancillary genetic studies.

Monoclonal B-cell lymphocytosis in the bone marrow: revisiting the criteria for chronic lymphocytic leukemia/small lymphocytic lymphoma.

Monoclonal B-cell lymphocytosis is a clonal B-cell population in the peripheral blood (PB) of <5x10ˆ9/L without extramedullary (EM) disease, often with a chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) phenotype. The degree of bone marrow (BM) involvement is not currently a part of the diagnostic criteria for MBL or CLL/SLL, but CLL-type MBLs in BM can be seen in patients lacking PB lymphocytosis. Data are limited on the outcome of such cases. We assessed the clinicopathologic characteristics of isolated BM CLL-type MBL in patients who did not meet criteria for CLL/SLL. We evaluated BMs from 2006 to 2018 with CLL-like clonal B-cell populations in patients with a PB absolute lymphocyte count or monoclonal B-cell count of <5 × 109/L and without definite evidence of EM disease. We investigated the extent and pattern of marrow involvement, PB counts, flow cytometric data, genetics, concurrent hematopoietic diseases, and outcomes including progression and treatment. Thirty cases with BM MBL but <5x10E9/L PB monoclonal B cells and no EM disease were identified. Thirteen of 30 had additional hematopoietic neoplasms. The mean patient age was 74.1 years (median: 77 years, range: 43-91 years). No patients had lymphadenopathy (LAD) or splenomegaly by physical examination. By imaging, nine of 18 had LAD (8/9 < 1.5 cm) and four of 18 had splenomegaly but with other attributable etiologies. Mean PB absolute lymphocyte count (ALC) was 1.8×10E9/L (range: 0.5-5.0×10E9/L). Twenty-four of 30 (80%) had low-level (<20%) BM involvement by MBL, and among these, none with available follow-up data progressed to diagnostic CLL/SLL. Six of 30 (20%) had >20% marrow involvement by MBL. Four of 6 were treated for CLL/SLL due to cytopenias, despite not meeting diagnostic criteria, and all 4 were CD38 or ZAP70 positive and had cytogenetic abnormalities, including trisomy 12. One of 6 developed overt CLL/SLL 3 years later and had cytogenetic abnormalities at the time of MBL diagnosis. One of 6 was monitored without treatment but had no cytogenetic abnormalities.Isolated BM CLL-type MBL represents a diagnostic gray area, and this study highlights the range of clinical outcomes. All cases with <20% BM involvement did not require CLL-specific treatment or progress to CLL/SLL. In the 4 cases where treatment was initiated due to cytopenias, patients had ≥20% BM involvement, CD38 or ZAP70 expression, and cytogenetic abnormalities but lacked a PB ALC of ≥5x10E9/L or LAD ≥1.5 cm, suggesting that not all patients with clinically significant disease will meet criteria for CLL/SLL. The results also show that concurrent hematopoietic disorders can complicate the diagnosis, as the disease course or treatment may result in leukopenia, precluding PB absolute lymphocytosis. Though larger studies are needed, the degree of BM involvement, in conjunction with flow cytometric prognostic markers, and cytogenetic abnormalities may be a useful addition to the current diagnostic criteria for CLL/SLL which only considers a PB numerical cutoff and EM involvement.

Identification of a Cancer-Predisposing Germline POT1 p.Ile49Metfs*7 Variant by Targeted Sequencing of a Splenic Marginal Zone Lymphoma.

Germline disruptive variants in Protection of Telomeres 1 (POT1) predispose to a wide variety of cancers, including melanoma, chronic lymphocytic leukemia (CLL), Hodgkin lymphoma, myeloproliferative neoplasms, and glioma. We report the first case of splenic marginal zone lymphoma (SMZL) arising in a patient with a germline POT1 variant: a 65-year-old male with an extensive history of cancer, including melanoma and papillary thyroid carcinoma, who presented with circulating atypical lymphocytosis. Bone marrow biopsy revealed 20% involvement by a CD5-CD10- B-cell lymphoma that was difficult to classify. During the clinical workup of his low-grade lymphoma, targeted next-generation sequencing (NGS) identified POT1 p.I49Mfs*7 (NM_015450:c. 147delT) at a variant allele frequency (VAF) of 51%. NGS of skin fibroblasts confirmed the POT1 variant was germline. This likely pathogenic POT1 loss-of-function variant has only been reported once before as a germline variant in a patient with glioma and likely represents one of the most deleterious germline POT1 variants ever linked to familial cancer. The spectrum of cancers associated with germline pathogenic POT1 variants (i.e., autosomal dominant POT1 tumor predisposition syndrome) should potentially be expanded to include SMZL, a disease often associated with the loss of chromosome 7q: the location of the POT1 genetic locus (7q31.33).

Flow Cytometric Findings in Clonal Cytopenia of Undetermined Significance.

OBJECTIVES: To examine flow cytometric (FCM) findings in clonal cytopenia of undetermined significance (CCUS) in relation to variant allele fraction (VAF) and mutation risk. METHODS: Nine FCM parameters, including 5 FCM metrics (Meyerson-Alayed scoring scheme [MASS] parameters) we previously used to identify myelodysplastic syndromes (MDS), were compared among 96 CCUS samples, 100 low-grade MDS samples and 100 samples from patients without somatic alterations (controls). RESULTS: FCM findings did not differ between CCUS samples with less than 20% VAF and controls. CCUS samples with more than 20% VAF (CCUS >20% VAF) demonstrated more than 1 abnormal FCM parameter at a frequency between MDS and controls. Abnormalities in CCUS with high-risk alterations (CCUS(hi)) were similar to MDS, with no statistical difference in the percentage of cases with more than 1 FCM abnormality or a positive MASS score. The positive predictive value (PPV) for clinically significant myeloid processes; MDS, CCUS(hi), and CCUS >20% VAF compared with other CCUS samples and controls was 94.8%, with 96.5% specificity and 61% sensitivity using a modified MASS score. A subset of MDS (43%) was distinguished from CCUS(hi) and CCUS >20% VAF using 3 parameters, with a 93.5% PPV and 83.3% specificity. CONCLUSIONS: FCM abnormalities can distinguish high-risk CCUS based on VAF or alteration type from low-risk CCUS and MDS in many cases. The findings are of potential utility in the evaluation of patients with cytopenias.

Defects in osteoblast function but no changes in long-term repopulating potential of hematopoietic stem cells in a mouse chronic inflammatory arthritis model.

Recent studies support the notion that there is an intricate relationship between hematopoiesis and bone homeostasis in normal steady states. Using mice undergoing chronic inflammatory arthritis, we investigated the relationship between hematopoiesis and bone homeostasis in pathologic conditions. We demonstrate that mice undergoing chronic inflammatory arthritis displayed osteoporosis resulting from a severe defect in osteoblast function. Despite the defective osteoblast function, however, the hematopoietic stem cells from these mice exhibited normal properties in either long-term repopulation or cell cycling. Therefore, the bone-forming capacity of osteoblasts is distinct from their ability to maintain hematopoietic stem cells in chronic inflammatory conditions.

Clinical Utility of Targeted Next-Generation Sequencing in the Evaluation of Low-Grade Lymphoproliferative Disorders.

OBJECTIVES: We investigated the usefulness of a custom-designed 31-gene next-generation sequencing (NGS) panel implemented on a routine basis for the evaluation of low-grade lymphoproliferative disorders (LPDs). METHODS: In total, 147 blood, bone marrow, and tissue specimens were sequenced, including 81% B-cell, 15% T-cell, and 3% natural killer (NK)-cell neoplasms. RESULTS: Of the cases, 92 (63%) of 147 displayed at least one pathogenic variant while 41 (28%) of 147 had two or more. Low mutation rates were noted in monoclonal B-cell lymphocytoses and samples with small T- and NK-cell clones of uncertain significance. Pathogenic molecular variants were described in specific disorders and classified according to their diagnostic, prognostic, and potential therapeutic value. Diagnostically, in addition to confirming the diagnosis of 15 of 15 lymphoplasmacytic lymphomas, 10 of 12 T large granular lymphocytic leukemias, and 2 of 2 hairy cell leukemias (HCLs), the panel helped resolve the diagnosis of 10 (62.5%) of 16 challenging cases lacking a specified diagnosis based on standard morphology, phenotype, and genetic analysis. CONCLUSIONS: Overall, implementation of this targeted lymphoid NGS panel as part of regular hematopathology practice was found to be a beneficial adjunct in the evaluation of low-grade LPDs.

Combined Targeted Therapy for BRAF-Mutant, Treatment-Related Acute Myeloid Leukemia.

A 44-year-old woman with a prior history of myxoid liposarcoma who was previously treated with radiation, chemotherapy, and resection, was admitted with syncope and pancytopenia. She was diagnosed with a high-grade therapy-related myelodysplastic syndrome and treated with decitabine. Her disease soon progressed to overt acute myeloid leukemia (AML). She was treated with cytotoxic chemotherapy including cytarabine and topotecan, but she was not a candidate for further anthracycline exposure given her prior treatment for sarcoma and concern for cardiotoxicity. Her AML was refractory to two sequential induction regimens. Given that targeted genomic sequencing had revealed a BRAF V600E mutation with a high allelic fraction, she was then placed on combined targeted BRAF/MEK therapy with dabrafenib and trametinib for her refractory disease. This resulted in a dramatic response with clearance of circulating myeloblasts, restoration of normal hematopoiesis, a significant decrease in marrow leukemic burden, and a concordant decrease in the BRAF V600E allelic burden. The response was transient, however, with a rapid increase in circulating blasts a few weeks later. At the time of subsequent progression, four separate KRAS mutations were identified. She died approximately 4 months after her diagnosis from rapidly progressive AML.

Pure White Cell Aplasia and Necrotizing Myositis.

Pure white cell aplasia (PWCA) is a rare hematologic disorder characterized by the absence of neutrophil lineages in the bone marrow with intact megakaryopoiesis and erythropoiesis. PWCA has been associated with autoimmune, drug-induced, and viral exposures. Here, we report a case of a 74-year-old female who presented with severe proximal weakness without pain and was found to have PWCA with nonspecific inflammatory necrotizing myositis and acute liver injury on biopsies. These findings were associated with a recent course of azithromycin and her daily use of a statin. Myositis improved on prednisone but PWCA persisted. With intravenous immunoglobulin and granulocyte-colony stimulating factor therapies, her symptoms and neutrophil counts improved and were sustained for months.