Comprehensive morphologic characterization of bone marrow biopsy findings in a large cohort of patients with VEXAS syndrome: A single-institution longitudinal study of 111 bone marrow samples from 52 patients

OBJECTIVES

VEXAS syndrome is an adult-onset autoinflammatory disease caused by a somatic pathogenic mutation in the UBA1 (ubiquitin-like modifier activating enzyme 1) gene. Patients present with rheumatologic manifestations and cytopenias and may have an increased predisposition to myelodysplastic syndrome (MDS) and plasma cell neoplasms. Prior studies have reported on the peripheral blood and bone marrow findings in patients with VEXAS syndrome. Due to the protean clinical presentation and lack of specificity of morphologic features (eg, vacuoles in early erythroid and granulocytic precursors), an optimal screening methodology to identify these patients in a timely fashion is desirable.

METHODS

To further evaluate and describe the salient diagnostic morphologic features in VEXAS syndrome, we carried out a comprehensive study of the largest single-institution cohort to date. Diagnostic and follow-up bone marrow biopsy specimens from 52 male patients with molecularly identified VEXAS syndrome underwent central review.

RESULTS

Cytopenias were common in all cases, primarily macrocytic anemia, monocytopenia, and thrombocytopenia. Bone marrow aspirate and biopsy were often hypercellular, with an increased myeloid/erythroid ratio, granulocytic hyperplasia with left shift, erythroid left shift, and megakaryocyte hyperplasia, which exhibited a range of striking morphologic findings. Distinctly vacuolated myeloid and erythroid precursors were seen in more than 95% of cases.

CONCLUSIONS

Our data reveal potential novel diagnostic features, such as a high incidence of monocytopenia and distinct patterns of atypical megakaryopoiesis, that appear different from dysmegakaryopoiesis typically associated with MDS. In our experience, those findings are suggestive of VEXAS, in the appropriate clinical context.

Clinical and molecular correlates of somatic and germline DDX41 variants in patients and families with myeloid neoplasms

The diagnosis of germline predisposition to myeloid neoplasms (MN) secondary to DDX41 variants is currently hindered by the long latency period, variable family histories and the frequent occurrence of DDX41 variants of uncertain significance (VUS). We reviewed 4,524 consecutive patients who underwent targeted sequencing for suspected or known MN and analyzed the clinical impact and relevance of DDX41VUS in comparison to DDX41path variants. Among 107 patients (44 [0.9%] DDX41path and 63 DDX41VUS [1.4%; 11 patients with both DDX41path and DDX41VUS]), we identified 17 unique DDX41path and 45 DDX41VUS variants: 24 (23%) and 77 (72%) patients had proven and presumed germline DDX41 variants, respectively. The median age was similar between DDX41path and DDX41VUS (66 vs. 62 years; P=0.41). The median variant allele frequency (VAF) (47% vs. 48%; P=0.62), frequency of somatic myeloid co-mutations (34% vs 25%; P= 0.28), cytogenetic abnormalities (16% vs. 12%; P=>0.99) and family history of hematological malignancies (20% vs. 33%; P=0.59) were comparable between the two groups. Time to treatment in months (1.53 vs. 0.3; P=0.16) and proportion of patients progressing to acute myeloid leukemia (14% vs. 11%; P=0.68), were similar. The median overall survival in patients with high-risk myelodysplastic syndrome/acute myloid leukemia was 63.4 and 55.7 months in the context of DDX41path and DDX41VUS, respectively (P=0.93). Comparable molecular profiles and clinical outcomes among DDX41path and DDX41VUS patients highlights the need for a comprehensive DDX41 variant interrogation/classification system, to improve surveillance and management strategies in patients and families with germline DDX41 predisposition syndromes.

Follicular lymphoma and diffuse large B-cell lymphoma with BCL2 and IRF4 rearrangements in adult patients

Follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL) with concurrent BCL2 and IRF4 rearrangements are rare. It is unclear whether such cases should be classified as large B- cell lymphoma with IRF4 rearrangement or FL/DLBCL-not otherwise specified. We identified 5 adult patients (FL, N = 3 and FL/DLBCL, N = 2) with concurrent BCL2 and IRF4 rearrangements. The median age at presentation was 77 years, and three patients presented with advanced stage disease. Both nodal and extranodal sites were involved and involvement was not limited to head and neck region. With a median follow-up of 18 months, 1 patient died and 4 patients were alive, including 3 who received chemotherapy and 1 who was observed. The neoplasms were histologically heterogeneous, including grade 2 and 3 FL and DLBCL. Four cases coexpressed CD10, BCL6, BCL2 and MUM1/IRF4. The Ki67 labelling index ranged from 20% to 95%. In 4 patients, the percentage of cells with BCL2 rearrangement was equal to or slightly greater than the cells harboring IRF4 rearrangement. Two cases underwent next generation sequencing tailored for lymphoid neoplasms. Both lacked mutations involving IRF4 and NF-kB pathway genes that are frequently detected in large B-cell lymphoma with IRF4 rearrangement, and one case showed DLBCL-EZH2 type mutations, including KMT2D and BCL2 mutations, similar to 2 previously reported DLBCL with BCL2 and IRF4 rearrangements. Adults with FL and FL/DLBCL with BCL2 and IRF4 rearrangements display clinicopathologic and mutational features more akin to FL and DLBCL and should not be characterized as large B-cell lymphoma with IRF4 rearrangement.

U2AF1 pathogenic variants in myeloid neoplasms and precursor states: distribution of co-mutations and prognostic heterogeneity

We have previously recognized the genotypic and prognostic heterogeneity of U2AF1 mutations (MT) in myelofibrosis (MF) and myelodysplastic syndromes (MDS). In the current study, we considered 179 U2AF1-mutated patients with clonal cytopenia of undetermined significance (CCUS; n = 22), MDS (n = 108), MDS/acute myeloid leukemia (AML; n = 18) and AML (n = 31). U2AF1 variants included S34 (60%), Q157 (35%), and others (5%): corresponding mutational frequencies were 45%, 55%, and 0% in CCUS; 57%, 39%, and 4% in MDS; 61%, 33%, and 6% in MDS/AML; and 55%, 35% and 10% in AML (P = 0.17, 0.36 and 0.09), respectively. Concurrent mutations included ASXL1 (37%), BCOR (19%), RUNX1 (14%), TET2 (15%), DNMT3A (10%), NRAS/KRAS (8%), TP53 (8%), JAK2 (5.5%) and SETBP1 (5%). The two most frequent U2AF1 MT were S34F (n = 97) and Q157P (n = 46); concurrent MT were more likely to be seen with the latter (91% vs 74%; P = 0.01) and abnormal karyotype with the former (70% vs 62%; P = 0.05). U2AF1 S34F MT clustered with BCOR (P = 0.04) and Q157P MT with ASXL1 (P = 0.01) and TP53 (P = 0.03). The median overall survival (OS) in months was significantly worse in AML (14.2) vs MDS/AML (27.3) vs MDS (33.7; P = 0.001); the latter had similar OS with CCUS (30.0). In morphologically high-risk disease (n = 49), defined by ≥10% blood or bone marrow blasts (i.e., AML or MDS/AML), median OS was 14.2 with Q157P vs 37.1 months in the presence of S34F (P = 0.008); transplant-adjusted multivariable analysis confirmed the detrimental impact of Q157P (P = 0.01) on survival and also identified JAK2 MT as an additional risk factor (P = 0.02). OS was favorably affected by allogeneic hematopoietic stem cell transplantation (HR: 0.16, 95% CI; 0.04-0.61, P = 0.007). The current study defines the prevalence and co-mutational profiles of U2AF1 pathogenic variants in AML, MDS/AML, MDS, and CCUS, and suggests prognostic heterogeneity in patients with ≥10% blasts.

Spectrum of clonal hematopoiesis in VEXAS syndrome

Vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic (VEXAS) syndrome is caused by somatic mutations in UBA1 (UBA1mut) and characterized by heterogenous systemic autoinflammation and progressive hematologic manifestations, meeting criteria for myelodysplastic syndrome (MDS) and plasma cell dyscrasias. The landscape of myeloid-related gene mutations leading to typical clonal hematopoiesis (CH) in these patients is unknown. Retrospectively, we screened 80 patients with VEXAS for CH in their peripheral blood (PB) and correlated the findings with clinical outcomes in 77 of them. UBA1mut were most common at hot spot p.M41 (median variant allele frequency [VAF] = 75%). Typical CH mutations cooccurred with UBA1mut in 60% of patients, mostly in DNMT3A and TET2, and were not associated with inflammatory or hematologic manifestations. In prospective single-cell proteogenomic sequencing (scDNA), UBA1mut was the dominant clone, present mostly in branched clonal trajectories. Based on integrated bulk and scDNA analyses, clonality in VEXAS followed 2 major patterns: with either typical CH preceding UBA1mut selection in a clone (pattern 1) or occurring as an UBA1mut subclone or in independent clones (pattern 2). VAF in the PB differed markedly between DNMT3A and TET2 clones (median VAF of 25% vs 1%). DNMT3A and TET2 clones associated with hierarchies representing patterns 1 and 2, respectively. Overall survival for all patients was 60% at 10 years. Transfusion-dependent anemia, moderate thrombocytopenia, and typical CH mutations, each correlated with poor outcome. In VEXAS, UBA1mut cells are the primary cause of systemic inflammation and marrow failure, being a new molecularly defined somatic entity associated with MDS. VEXAS-associated MDS is distinct from classical MDS in its presentation and clinical course.

Abnormal CD13/HLA-DR Expression Pattern on Myeloblasts Predicts Development of Myeloid Neoplasia in Patients With Clonal Cytopenia of Undetermined Significance

OBJECTIVES

Patients with clonal cytopenia of undetermined significance (CCUS) are at increased risk of developing myeloid neoplasia (MN). We evaluated whether a simple flow cytometry immunophenotyping (FCIP) assay could differentiate the risk of development of MN in patients with CCUS.

METHODS

Bone marrow aspirates were assessed by FCIP panel in a cohort of 80 patients identified as having CCUS based on next-generation sequencing or cytogenetics from March 2015 to May 2020, with available samples. Flow cytometric assay included CD13/HLA-DR expression pattern on CD34-positive myeloblasts; CD13/CD16 pattern on maturing granulocytic precursors; and aberrant expression of CD2, CD7, or CD56 on CD34-positive myeloblasts. Relevant demographic, comorbidity, and clinical and laboratory data, including the type and extent of genetic abnormalities, were extracted from the electronic health record.

RESULTS

In total, 17 (21%) patients with CCUS developed MN over the follow-up period (median survival follow-up, 28 months [95% confidence interval, 19-31]). Flow cytometry immunophenotyping abnormalities, including the aberrant pattern of CD13/HLA-DR expression, as detected at the time of the diagnosis of CCUS, were significantly associated with risk of developing MN (hazard ratio, 2.97; P = .006). Additional FCIP parameters associated with the development of MN included abnormal expression of CD7 on myeloblasts and the presence vs absence of any FCIP abnormality.

CONCLUSIONS

A simple FCIP approach that includes assessment of CD13/HLA-DR pattern on CD34-positive myeloblasts can be useful in identifying patients with CCUS at higher risk of developing MN.

A dynamic 3-factor survival model for acute myeloid leukemia that accounts for response to induction chemotherapy

The current study was approached with the assumption that response to induction chemotherapy, in acute myeloid leukemia (AML), overshadows pre-treatment risk variables in predicting survival and therefore be used as an anchor for a simplified risk model. We considered 759 intensively-treated patients with AML, not promyelocytic: median age 60 years; primary 66%, secondary 25%, and therapy-related 9%; European LeukemiaNet cytogenetic risk category favorable 8%, intermediate 61%, and adverse 31%. Complete remission with (CR) or without (CRi) count recovery was achieved in 608 (80%) patients. After a median follow-up of 22 months, 503 deaths, 272 relapses, and 257 allogeneic hematopoietic stem cell transplants (AHSCTs) were recorded. Multivariable analysis identified failure to achieve CR/CRi (HR 3.8, 95% CI 3.1-4.8), adverse karyotype (2.2, 1.8-2.8), and age >55 years (2.1, 1.6-2.7) as main risk factors for survival. HR-weighted scoring resulted in four-tiered risk stratification: low (0 points; N=183), intermediate-1 (1 point; N=331), intermediate-2 (2 points; N=117), and high (≥3 points; N=128), with respective median survival (5-year rate) not reached (68%), 34 (37%), 13 (20%), and 5 (5%) months (p <0.001). FLT3-ITD mutation was associated with inferior survival in intermediate-1 (p=0.004) and TP53 in intermediate-2 (p=0.06) and high (p=0.02) risk disease; the latter was fully accounted for by the close association between TP53 mutation and complex/monosomal karyotype while the observations regarding FLT3-ITD were not affected by treatment with midostaurin. AHSCT had a favorable impact on survival, most apparent in intermediate-1 (p<0.001), intermediate-2 (p=0.03), and high (p=0.01) risk disease. The proposed 3-factor survival model offers a novel prototype that is amenable to further enhancement by molecular information and was validated in an external cohort of 1,032 intensively-treated AML patients. This article is protected by copyright. All rights reserved.

Characteristics and prognosis of mutated STAG2 myeloid neoplasms

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Background: Stromal Antigen 2 ( STAG2), located on Xq25, is the most mutated (m) cohesin-complex gene in myeloid neoplasm (MN) patients (pts). mSTAG2 is present in around 5% of MN and has been linked to secondary AML and potential poor impact on outcome. Methods: We retrospectively screened MN pts who had next-generation sequencing (NGS) (OncoHeme) performed at Mayo Clinic between 2018-2021. m STAG2 pts were included at the date of NGS. Charts were reviewed for clinical information after obtaining IRB approval. BlueSky Software V7.40 was used for statistical analysis. Results: Characteristics: 70 pts with mSTAG2 MN were identified, their median age was 72 years (range 25-91); with 55 pts (79%) being males. Complete blood counts showed median white blood cell count of 2.8 x109/L, hemoglobin of 8.9 gm/dL and platelets of 89 x109/L. The diagnosis was MDS in 38 pts (54%), AML in 20 (29%), MDS/MPN in 9 (13%), MPN in 2 (3%), and CCUS in 1 (1%). 11 cases (16%) were defined as therapy-related MN (tMN). Cytogenetics were normal in 45 pts (64%) and abnormal in 22 (31%). 10/50 non-AML pts progressed to AML (after median time of 9.8 months). Hematopoietic cell transplantation (HCT) was done in 20 pts (29%). mSTAG2: median VAF (mVAF) was 50% (range, 5%-100%). Males had higher mVAF compared to females (64% vs. 27%, p= .001), and tMN pts had higher mVAF compared to de novo (dn) MN pts (66% vs. 43%, p= .03). mVAF had no correlation with disease classification (50% in AML, 52% in MDS, 41% in MDS/MPN, 36% in MPN and 5% in CCUS, p= .5). STAG2 mutations were nonsense, frameshift, and splice site in 50%, 37%, and 13%, respectively. Co-mutations : median number of co-mutations was 3 (range, 0-6). Most common co-mutations were ASXL1 (66%), SRSF2 (37%), TET2 (36%), RUNX1 (29%), IDH2 (21%), BCOR (20%) and U2AF1 (16%) while least common were TP53, SETBP and ZRSR2 (1% each). Neither number (p= .08) nor type of co-mutation correlated with MN classification. There was no difference in the co-mutational pattern between tMN and dnMN pts. Survival : median overall survival (mOS) was 16.3 months with a median follow up time of 24.5 months. Pts who received HCT had better OS compared to non-HCT pts (mOS not reached vs. 14.9 months, p= .003). Pts with an isolated m STAG2 had better OS than co-mutated pts (p= .04), while the type of STAG2 mutation did not affect OS (p= .3). Pts with tMN had worse OS than dnMN pts (9.9 vs. 20.4 months, p= .02). VAF ≥75% had a negative impact on OS (20.5 vs 8.1 months, p= .008). mOS did not differ based on MN diagnosis. On multivariate analysis, only HCT (HR 0.3, p= .01) and VAF ≥75% (HR 2.3, p= .02) had impact on OS. Conclusions: mSTAG2 was more common in elderly males and MDS diagnosis. mSTAG2 was uncommon as an isolated mutation, indicating a possible role in disease progression with preferred certain co-mutations ( ASXL1/SRSF2/RUNX1/IDH2). mOS was poor regardless of MN diagnosis indicating a molecularly driven significance of an aggressive disease. The study needs to be validated by larger studies.

Characteristics and prognosis of DDX41- and GATA2-mutated myeloid neoplasms

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Background: Mutated DEAD-box helicase 41 (m DDX41), and mutated GATA2 are germline mutations associated with familial predisposition syndromes. In this study, we compare the clinical characteristics and survival outcomes (OS) of m DDX41 and m GATA2 MN patients (pts). Methods: We retrospectively screened pts who had next-generation sequencing (NGS) (OncoHeme panel) performed at Mayo Clinic. 4,524 consecutive pts (2018-2021) were screened for DDX41 mutations and 3,872 for GATA2 mutations (2015-2020) and included 36 MN pts with m DDX41 genetic alterations, and 55 m GATA2 MN pts. m GATA2 cases were included at NGS date while m DDX41 were included at diagnosis date. Germline workup was not done in all cases. JMP 16.2.0 Software was used for statistical analysis. Results: Patient characteristics: The most common diagnosis was MDS (N = 22, 61% in m DDX41 N = 17, 31% in m GATA2 group; p = .0044). MDS/MPN overlap was seen in m GATA2 group only; (29% vs. 0%; p = .0004). Majority of pts were males with median age of 68 and 67 years for m DDX41 and m GATA2 pts; respectively (p = .7). m DDX41 pts had higher hemoglobin, platelets, and MCV (< .0001, 0.005, < .0001; respectively) and significantly lower white blood cells (WBC) count compared to m GATA2 pts (< .0001). All m DDX41-AML pts were (ELN) intermediate-risk, and 64% of m DDX41 MDS were intermediate risk (IPSS-R). In contrast, of m GATA2 pts 62% of AML were adverse risk and 44% of MDS very high risk. Majority of m DDX41 pts had normal karyotype (N = 32; 91% vs. N = 19, 37%; p < .0001), had isolated mutations (N = 23; 64%) and the most common co-mutations were DNMT3A (38%), ASXL1 (30%), JAK2 (23%). The majority of m GATA2 pts were co-mutated (96%) with a different co-mutation pattern ASXL1 (60%), SRSF2 (34%), RUNX1 (19%). Germline data: One m GATA2 pts had proven germline mutation, and 10/11 (91%) m DDX41 pts were confirmed Survival and progression in MDS/AML: After median follow-up of 30 months in MDS/AML, 7 (21%) m DDX41 and 23 (77%) m GATA2 pts died with superior OS in m DDX41 compared to m GATA2 pts with median OS of (136.7 vs. 6.8 months, p < .0001). Seven (31%) of 22 m DDX41 and 6 (35%) m GATA2 MDS pts progressed into AML with a median time to progression of (11.2 vs. 5.2 months, p = .045). The leukemia free survival (LFS) for m DDX41 MDS pts was significantly longer than LFS of m GATA2 MDS pts (24.4 vs. 6 months, p < .0001). Conclusions: We compare the outcomes of two unique mutations associated with germline predisposition. We found m DDX41 pts had fewer cytogenetic aberrations, no MDS/MPN overlap, and lower WBC count. Majority of m DDX41 MDS/AML pts were intermediate risk category, compared to predominance of adverse risk disease in m GATA2 pts, translating into better OS and LFS. This study is limited by the small size, lack of germline workup in all cases, and retrospective nature. However, it supports the favorable prognosis and indolent course of m DDX41 pts recently described.

DNMT3A R882 Mutations Confer Unique Clinicopathologic Features in MDS Including a High Risk of AML Transformation

DNMT3A mutations play a prominent role in clonal hematopoiesis and myeloid neoplasms with arginine (R)882 as a hotspot, however the clinical implications of R882 vs. non-R882 mutations in myeloid neoplasms like myelodysplastic syndrome (MDS) is unclear. By data mining with publicly accessible cancer genomics databases and a clinical genomic database from a tertiary medical institution, DNMT3A R882 mutations were found to be enriched in AML (53% of all DNMT3A mutations) but decreased in frequency in clonal hematopoiesis of indeterminate potential (CHIP) (10.6%) or other myeloid neoplasms including MDS (27%) (p<.001). Next with the largest cohort of patients with DNMT3A R882 mutant MDS known to date from multiple institutions, DNMT3A R882 mutant MDS cases were shown to have more severe leukopenia, enriched SRSF2 and IDH2 mutations, increased cases with excess blasts (47% vs 22.5%, p=.004), markedly increased risk of AML transformation (25.8%, vs. 1.7%, p=.0001) and a worse progression-free survival (PFS) (median 20.3, vs. >50 months, p=.009) than non-R882 mutant MDS cases. DNMT3A R882 mutation is an independent risk factor for worse PFS, and importantly the differences in the risk of AML transformation between R882 vs. non-R882 mutant patients cannot be explained by different treatment approaches. Interestingly the higher risk of AML transformation and the worse PFS in DNMT3A R882 mutant MDS cases are mitigated by coexisting SF3B1 or SRSF2 mutations. The unique clinicopathologic features of DNMT3A R882 mutant MDS shed light on the prognostic and therapeutic implications of DNMT3A R882 mutations.

Spectrum of hematological malignancies, clonal evolution and outcomes in 144 Mayo Clinic patients with germline predisposition syndromes

Germline predisposition syndromes (GPS) result from constitutional aberrations in tumor suppressive and homeostatic genes, increasing risk for neoplasia in affected kindred. In this study, we present clinical and genomic data on 144 Mayo Clinic patients with GPS; 59 evaluated prospectively using an algorithm-based diagnostic approach in the setting of a dedicated GPS/ inherited bone marrow failure syndrome (IBMFS) clinic. Seventy-two (50%) patients had IBMFS (telomere biology disorders-32,Fanconi anemia-18, Diamond Blackfan Anemia - 11, congenital neutropenia-5, Schwachman-Diamond Syndrome-5 and Bloom Syndrome-1), 27 (19%) had GPS with antecedent thrombocytopenia (RUNX1-FPD-15, ANKRD26-6, ETV6-2, GATA1-1, MPL-3), 28 (19%) had GPS without antecedent thrombocytopenia (GATA2 haploinsufficiency-16, DDX41-10, CBL-1 and CEBPA-1) and 17 (12%) had general cancer predisposition syndromes (ataxia telangiectasia-7, heterozygous ATM variants-3, CHEK2-2, TP53-2, CDK2NA-1, NF1-1 and Nijmegen Breakage Syndrome-1). Homozygous and heterozygous ATM pathogenic variants were exclusively associated with lymphoproliferative disorders (LPD), while DDX41 GPS was associated with LPD and myeloid neoplasms. The use of somatic NGS-testing identified clonal evolution in GPS patients, with ASXL1, RAS pathway genes, SRSF2 and TET2 being most frequently mutated. Fifty-two (91%) of 59 prospectively identified GPS patients had a change in their management approach, including additional GPS-related screening in 42 (71%), referral for allogenic HSCT workup and screening of related donors in 16 (27%), medication initiation and selection of specific conditioning regimens in 14 (24%), and genetic counseling with specific intent of fertility preservation and preconceptual counseling in 10 (17%) patients; highlighting the importance of dedicated GPS screening, detection and management programs for patients with hematological neoplasms.

Clinicopathologic characteristics of myeloid neoplasms that harbor both a DDX41 germline and an acquired DDX41 genetic alteration

Introduction/Objective

Myeloid neoplasms associated with DDX41 germline genetic alterations are becoming increasingly recognized as a unique subset of hematologic cancer predisposition syndromes. As such, we sought to review their clinicopathologic characteristics.

Methods/Case Report

We searched our next-generation sequencing database for cases with two DDX41 variants; one variant at heterozygous variant allele fraction (VAF) indicating known or putative germline status, and second variant at low VAF consistent with an acquired subclone. We reviewed the clinicopathologic features.

Results (if a Case Study enter NA)

We identified 18 cases - male:female ratio 2.6:1, average age at presentation, 69 years (range 57-89). The diagnoses included no diagnostic abnormality (3), MDS-MLD (1), MDS-EB1 (1), increased blasts only(5-19%) (7), and AML (6). All had anemia [average hemoglobin (10.2) (range 6.5-12.9 g/dL)], 17/18 with thrombocytopenia [average 87 (range 22-222 K)], 17/18 with neutropenia [average absolute neutrophil count (ANC) (819) (range 90-1800)] and 13/18 with macrocytosis [average (101.5) (range 83.7-114 fL)]. Bone marrow cellularity (corrected for increased blasts &gt;20%) was predominantly hypocellular (11/19) followed by normocellular (5/19). 3/19 cases showed erythroid dysplasia; no cases demonstrated granulocytic dysplasia; 7/19 cases showed megakaryocytic dysplasia. Of non-AML cases, 8/12 cases showed increased blasts [average 10% (range 5-19%)]. Of 4 cases without an increase in blasts, 1 showed MDS, 2 no dysplasia [1 -ANC of 666 and preserved platelets (222); 2- thrombocytopenia with preserved ANC (1800)] and 1 had slight megakaryocytic atypia. 16/17 cases were karyotypically normal. 14/18 of the patients are alive (median follow-up, 48) (8-125 months).

Conclusion

This cohort finds that myeloid neoplasms arising from DDX41 germline predisposition syndrome tend to present in older individuals, have infrequent dysplasia and are associated with a prolonged clinical course despite elevated blast counts at diagnosis. Recognition of these disorders is challenging and DDX41 testing should be included as part of genetic profiling. The presence of a suspected DDX41 germline variant may prompt confirmatory and familial testing, particularly in the event a hematopoietic transplant is a treatment option.

Abstract B03: Acute megakaryoblastic leukemia is associated with poor overall survival and enriched in JAK2 variants

In this study, we aimed to characterize the molecular mechanisms of two very rare subtypes of AML: acute megakaryoblastic leukemia (AMKL) and acute panmyelosis with myelofibrosis (APMF). Our goal is to describe the clinical-pathologic features of APMF and explore the genomic landscape AMKL to further understand these rare malignancies. We identified 35 patients diagnosed with AMKL (n=27) and APMF (n=8) at Mayo Clinic between 1995 and 2015 by retrospective chart review. For 10 of the AMKL patients, tissue was available for whole-exome sequencing and was analyzed in comparison to a published AML reference population. The median overall survival was shorter in patients with AMKL (3.9 months, 95% CI 1.7-7.4) than in patients with APMF (14.3 months, 95% CI 0.7-NE, p = 0.026,). For both AMKL and APMF, patients who underwent allogeneic hematopoietic stem cell transplantation had better overall survival (14.3 months, 95% CI 1.9-NE) compared to those not undergoing transplantation (4.6 months, 95% CI 1.5-7.4, p = 0.003). Patients with AMKL presented more frequently with splenomegaly, with higher peripheral blood blast counts, and with higher serum lactate dehydrogenase concentrations. 9 out of 10 AMKL patients with available tissue for sequencing demonstrated variants in 22 of 35 AML driver genes, with JAK2 V617F as the most common mutation. Although our small study numbers preclude firm conclusions, it does reflect the rarity of these AML subtypes. Furthermore, inferior survival in AMKL (compared to APMF) was reflected in its proliferative disease features such as splenomegaly, high blast counts, and high lactate dehydrogenase. Interestingly, the presence of JAK2 V617F variants in 40% of the interrogated samples was higher than expected. Although JAK2 is a known molecular driver in myeloproliferative neoplasms, it is actually very rare in de novo AML (~1%). Despite improved survival with allogeneic stem cell transplant, we can conclude that treatment outcomes for AMKL and APMF with standard-of-care therapy were sobering and that patients with these rare AML subtypes should undergo molecular evaluation to qualify them for clinical trials with novel targeted therapies.

Citation Format: Marissa Li, Moritz Binder, Basma Basha, Ben Zhang, Alejandro Ferrer, Yuanhan Liu, Mrinal Patnaik, David Viswanatha, Naseema Gangat. Acute megakaryoblastic leukemia is associated with poor overall survival and enriched in JAK2 variants [abstract]. In: Proceedings of the AACR Special Conference on the Evolving Landscape of Cancer Modeling; 2020 Mar 2-5; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2020;80(11 Suppl):Abstract nr B03.

Mayo Alliance Prognostic Model for Myelodysplastic Syndromes: Integration of Genetic and Clinical Information

OBJECTIVE

To develop a new risk model for primary myelodysplastic syndromes (MDS) that integrates information on mutations, karyotype, and clinical variables.

PATIENTS AND METHODS

Patients with World Health Organization-defined primary MDS seen at Mayo Clinic (MC) from December 28, 1994, through December 19, 2017, constituted the core study group. The National Taiwan University Hospital (NTUH) provided the validation cohort. Model performance, compared with the revised International Prognostic Scoring System, was assessed by Akaike information criterion and area under the curve estimates.

RESULTS

The study group consisted of 685 molecularly annotated patients from MC (357) and NTUH (328). Multivariate analysis of the MC cohort identified monosomal karyotype (hazard ratio [HR], 5.2; 95% CI, 3.1-8.6), "non-MK abnormalities other than single/double del(5q)" (HR, 1.8; 95% CI, 1.3-2.6), RUNX1 (HR, 2.0; 95% CI, 1.2-3.1) and ASXL1 (HR, 1.7; 95% CI, 1.2-2.3) mutations, absence of SF3B1 mutations (HR, 1.6; 95% CI, 1.1-2.4), age greater than 70 years (HR, 2.2; 95% CI, 1.6-3.1), hemoglobin level less than 8 g/dL in women or less than 9 g/dL in men (HR, 2.3; 95% CI, 1.7-3.1), platelet count less than 75 × 10⁹/L (HR, 1.5; 95% CI, 1.1-2.1), and 10% or more bone marrow blasts (HR, 1.7; 95% CI, 1.1-2.8) as predictors of inferior overall survival. Based on HR-weighted risk scores, a 4-tiered Mayo alliance prognostic model for MDS was devised: low (89 patients), intermediate-1 (104), intermediate-2 (95), and high (69); respective median survivals (5-year overall survival rates) were 85 (73%), 42 (34%), 22 (7%), and 9 months (0%). The Mayo alliance model was subsequently validated by using the external NTUH cohort and, compared with the revised International Prognostic Scoring System, displayed favorable Akaike information criterion (1865 vs 1943) and area under the curve (0.87 vs 0.76) values.

CONCLUSION

We propose a simple and contemporary risk model for MDS that is based on a limited set of genetic and clinical variables.

Defining Lymphoplasmacytic Lymphoma: Does MYD88L265P Define a Pathologically Distinct Entity Among Patients With an IgM Paraprotein and Bone Marrow-Based Low-Grade B-Cell Lymphomas With Plasmacytic Differentiation?

OBJECTIVES

Lymphoplasmacytic lymphoma (LPL) remains a poorly defined entity, even with the discovery of MYD88L265P mutations and association with Waldenström macroglobulinemia (WM). Among bone marrow (BM)-based, low-grade B-cell lymphoma with plasmacytic differentiation (LGBLPD) and immunoglobulin M (IgM) paraproteins, we sought to determine whether MYD88L265P defines a distinct entity and can help refine diagnostic criteria for LPL.

METHODS

BMs diagnosed with LGBLPD or LPL and serum IgM paraprotein were studied (2007-2013). Clinicopathologic features were reviewed and specimens were tested for MYD88L265P.

RESULTS

In total, 138 (87%) of 159 cases had MYD88L265P, and 158 of 159 were clinically considered WM. MYD88L265P cases had higher disease burden than MYD88WT. Features associated with MYD88L265P include increased mast cells and lymphocyte (not plasma cell)-predominant infiltrate. Hemosiderin, Dutcher bodies, and paratrabecular growth were not associated with MYD88L265P.

CONCLUSIONS

Our data support a clinicopathologic approach to LPL diagnosis and recognition that it may manifest with varying morphologies, phenotypes, and molecular features.

Outcome of patients younger than 50 years old diagnosed with myelodysplastic syndromes (MDS): Single institution experience

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Background: Myelodysplastic syndromes (MDS) are rare hematological neoplasms typically seen in the elderly. Young MDS (yMDS) patients ( < 50 years old) have been reported to comprise between 3-6% in the Surveillance, Epidemiology and End Results (Ma X et al, Cancer 2007; Rollison R et al, Blood 2008) with a better overall survival (OS). Methods: 1012 MDS patients from 1993 to 2015 were found after IRB approval was obtained. All cases had their bone marrow slides reviewed at our institution. yMDS Patients were included as cohort 1, while the rest as cohort 2. Survival estimates were calculated using Kaplan-Meier curves and univariate and multivariate analyses was based on log-rank testing using JMP software version 10. Results: We found 68 (7%) yMDS patients with a median age of 42 years (range, 18-49). Female gender was more common (43% vs 31%, p = 0.05) while platelets were lower in yMDS (61 vs 102, p < 0.0001). Therapy related MDS (t-MDS) was more frequent (33% vs 17%, p = 0.005), as was transformation to acute myeloid leukemia (AML) in yMDS (28 % vs 11%, p = 0.0004). Allogenic hematopoietic cell transplantation (HCT) was more frequent in yMDS (42% vs 4%, p < 0.0001). Survival outcome: Median OS was longer for cohort 1 vs cohort 2 but did not reach statistical significance (43 vs 21 months, p = 0.1). Median progression free survival (PFS) was shorter for cohort 1 vs cohort 2 but also did not reach statistical significance (8 vs 12 months, p = 0.3). Median OS for cohort 1 based on R-IPSS was 44, 105, 40, 18, and 12 months for very low, low, intermediate, high and very high risk groups, respectively (p = 0.09). Median OS was shorter in t-MDS vs de novo MDS in yMDS (13 vs 47 months, p = 0.04). yMDS patients who transformed to AML had worse median OS (18 vs 93 months, p = 0.001). On multivariate analysis neither t-MDS nor R-IPSS had a statistically significant impact on OS. Conclusions: MDS is rarely diagnosed under the age of 50 with IPSS-R being less powerful in detecting mOS. Among yMDS patients, there was a higher proportion of t-MDS compared to older patients with subsequent higher rates of AML transformation and higher rates of allogeneic HCT. In our study, we did not find an improved OS for yMDS patients compared to older patients.

Panel sequencing for clinically oriented variant screening and copy number detection in 142 untreated multiple myeloma patients

We employed a customized Multiple Myeloma (MM)-specific Mutation Panel (M³P) to screen a homogenous cohort of 142 untreated MM patients for relevant mutations in a selection of disease-specific genes. M³Pv2.0 includes 77 genes selected for being either actionable targets, potentially related to drug–response or part of known key pathways in MM biology. We identified mutations in potentially actionable genes in 49% of patients and provided prognostic evidence of STAT3 mutations. This panel may serve as a practical alternative to more comprehensive sequencing approaches, providing genomic information in a timely and cost-effective manner, thus allowing clinically oriented variant screening in MM.

TP53 mutations and polymorphisms in primary myelofibrosis

A total of 107 patients with chronic-phase primary myelofibrosis (PMF) were screened for TP53 mutations, which were detected in 4 (4%) cases: (i) E204E; GAG>GAA (silent exon 6); (ii) G245D; GGC>GAC (exon 7); (iii) R175H; CGC>CAC (exon 5); and (iv) six base insert (GGCGAG) after bp13767 (exon 6). Three (75%) of the four TP53-mutated cases also carried JAK2V617F whereas none were positive for MPL or IDH mutations. Two of the four TP53 mutated cases were also screened for TET2, ASXL1, DNMT3A, and EZH2 mutations and were negative. There was no significant difference in presenting features or survival between TP53 mutated and unmutated cases. TP53 exon 4 single nucleotide polymporphism (SNPs) data for codon 72 were available on 104 patients and included 56% with homozygous Arg72Arg, 33% with heterozygous Pro72Arg, and 11% with homozygous Pro72Pro. There were no significant differences among the three codon 72 genotypes in terms of presenting characteristics or survival.

Laboratory practice guidelines for detecting and reporting BCR-ABL drug resistance mutations in chronic myelogenous leukemia and acute lymphoblastic leukemia: a report of the Association for Molecular Pathology

The BCR-ABL tyrosine kinase produced by the t(9;22)(q34;q11) translocation, also known as the Philadelphia chromosome, is the initiating event in chronic myeloid leukemia (CML) and Ph+ acute lymphoblastic leukemia (ALL). Targeting of BCR-ABL with tyrosine kinase inhibitors (TKIs) has resulted in rapid clinical responses in the vast majority of patients with CML and Philadelphia chromosome+ ALL. However, long-term use of TKIs occasionally results in emergence of therapy resistance, in part through the selection of clones with mutations in the BCR-ABL kinase domain. We present here an overview of the current practice in monitoring for such mutations, including the methods used, the clinical and laboratory criteria for triggering mutational analysis, and the guidelines for reporting BCR-ABL mutations. We also present a proposal for a public database for correlating mutational status with in vitro and in vivo responses to different TKIs to aid in the interpretation of mutation studies.

First report of autologous cord blood transplantation in the treatment of a child with leukemia

We present the case of a 3-year-old girl with acute lymphoblastic leukemia who developed isolated central nervous system relapse while receiving chemotherapy 10 months after diagnosis. The child achieved a second remission on retreatment with systemic and intrathecal chemotherapy. She then underwent myeloablative chemotherapy and radiation therapy followed by infusion of her own umbilical cord blood, which the parents had saved after her delivery. She is now doing well and is in complete remission 20 months after cord blood transplantation. In this first report of autologous cord blood transplantation for treatment of childhood leukemia, we discuss the safety and feasibility of this procedure as well as some of the uncertainties surrounding autologous cord blood collection and usage.

Peripheral T-cell lymphoma with extensive dendritic cell network mimicking follicular dendritic cell tumor: a case report with pathologic, immunophenotypic, and molecular findings

Peripheral T-cell lymphoma (PTCL) with a nodular pattern of growth is uncommon and may be misdiagnosed initially as a B-cell lymphoma or reactive process. We report a case of a rapidly growing PTCL with a distinctly nodular pattern in an axillary lymph node from an 89-year-old man. Immunohistochemical stains for CD21, CD23, and CD35 highlighted an extensive dendritic cell network that imparted the nodular appearance and, in addition, was associated intimately with the neoplastic cells. The neoplastic cells otherwise had an immunophenotype similar to previously reported cases of PTCL with a nodular pattern and germinal center origin (CD3+, CD4+, CD5+, bcl-6+, CD31+, subset CD10+, subset CXCL13+, and subset CD79a+). Molecular studies confirm a clonal T-cell receptor g gene rearrangement. This case emphasizes unusual morphologic features in a PTCL that may be mistaken for follicular lymphoma or a tumor of follicular dendritic cell origin.

Acute myeloid leukemia of donor origin after allogeneic bone marrow transplantation for precursor T-cell acute lymphoblastic leukemia: case report and review of the literature

We report a case of donor-derived acute myeloid leukemia (AML) occurring in a 33-year-old man after allogeneic bone marrow transplantation (BMT) for precursor T-cell acute lymphoblastic -leukemia (T-ALL). The cells for BMT were from his human leukocyte antigen (HLA)-matched sister. Fluorescence in-situ hybridization (FISH) analysis showed the AML to be of donor origin (i.e., karyotypically female) with an 11q23 (mixed lineage leukemia (MLL) gene) translocation, while the original T-ALL exhibited a male karyotype with abnormalities of chromosomes 6, 8, and a t(10;14)(q24;q11.2). Subsequent molecular short tandem repeat studies confirmed the AML to be of donor origin. Donor-cell leukemia (DCL) after allogeneic BMT is a rare, yet well-documented, event. Our report presents clinicopathologic information about a case of DCL and a review of the recent literature.

Nonsecretory variant of immunoproliferative small intestinal disease: a case report with pathologic, immunophenotypic, and molecular findings

We report a case of the nonsecretory variant of immunoproliferative small intestinal disease involving the distal small bowel and the mesenteric and retroperitoneal lymph nodes in a 19-year-old woman from Mexico. This variant extranodal marginal zone B-cell lymphoma appeared similar in the different sites of involvement, with more interspersed large cells and greater plasmacytic differentiation present in intestinal specimens. Characteristic lymphoepithelial lesions and follicular colonization were seen in intestinal and lymph node sections, respectively. The neoplastic B cells were cytoplasmic immunoglobulin (Ig) A heavy-chain restricted and lacked surface and cytoplasmic light-chain expression by flow cytometric analysis. Serum and urine protein electrophoresis/immunofixation revealed hypogammaglobulinemia with no paraprotein. Molecular studies showed absence of immunoglobulin heavy-chain (IgH) gene rearrangement, with a nonfunctional clonotypic rearrangement of the kappa light-chain gene. This case highlights the role for kappa light-chain gene evaluation in immunoproliferative small intestinal disease, because IgH gene rearrangement analysis is often negative.

Hodgkin and non-Hodgkin lymphoma involving bone marrow

The role of bone marrow examination in diagnosis and staging of patients with Hodgkin lymphoma, B-non-Hodgkin lymphoma, and T-non-Hodgkin lymphoma is reviewed. Optimal routine and specialized bone marrow examination techniques are discussed. The salient morphologic, immunophenotypic, and genetic features of mature and immature B, T neoplasms and classic Hodgkin lymphoma in bone marrow are delineated, along with recommendations to distinguish these overt neoplasms from non-neoplastic processes.

Minimal residual disease detection in childhood precursor-B-cell acute lymphoblastic leukemia: relation to other risk factors. A Children's Oncology Group study

Minimal residual disease (MRD) can be detected in the marrows of children undergoing chemotherapy either by flow cytometry or polymerase chain reaction. In this study, we used four-color flow cytometry to detect MRD in 1016 children undergoing therapy on Children's Oncology Group therapeutic protocols for precursor-B-cell ALL. Compliance was excellent, with follow-up samples received at the end of induction on nearly 95% of cases; sensitivity of detection at this time point was at least 1/10,000 in more than 90% of cases. Overall, 28.6% of patients had detectable MRD at the end of induction. Patients with M3 marrows at day 8 were much more likely to be MRD positive (MRD+) than those with M2 or M1 marrows. Different genetically defined groups of patients varied in their prevalence of MRD. Specifically, almost all patients with BCR-ABL had high levels of end-of-induction MRD. Only 8.4% of patients with TEL-AML1 were MRD+>0.01% compared with 20.3% of patients with trisomies of chromosomes 4 and 10. Our results show that MRD correlates with conventional measures of slow early response. However, the high frequency of MRD positivity in favorable trisomy patients suggests that the clinical significance of MRD positivity at the end of induction may not be the same in all patient groups.

Utility of immunohistochemistry in bone marrow evaluation of T-lineage large granular lymphocyte leukemia

Although T-lineage large granular lymphocyte (LGL) leukemia has been described for over 20 years, many patients with this neoplasm go unrecognized. Chief among the difficulties in diagnosing this entity is that the morphologic features are nonspecific and that it is difficult to distinguish it from reactive processes. The purpose of this study was to examine the histologic and immunophenotypic appearance of T-LGL leukemia in the peripheral blood and bone marrow, and to determine what features may suggest that ancillary studies such as flow cytometric and molecular analysis should be pursued to make a definitive diagnosis. We took a multidisciplinary approach by using morphology, immunoperoxidase staining, flow cytometric analysis, and molecular studies on 9 cases of T-lineage LGL leukemia. Our findings indicate that T-lineage LGL leukemia typically infiltrates the marrow diffusely. Most cases show a hypercellular marrow with an increase in myeloid precursors relative to the mature cells (i.e., an inversion of the myeloid maturation pyramid) and a decreased myeloid:erythroid ratio. Neutropenia without a left shift is usually seen in the peripheral blood. The tumor cells are usually CD3+, CD8+, CD57+, and TIA-1+. Most notably, the number of CD3+ T cells per high-power field is markedly elevated in T-LGL leukemia compared with normal, reactive, and pathologic marrows with neutropenia (mean values, 559 cells/mm(2) v. 7/mm(2), 11/mm(2), and 263/mm(2), respectively, P<.01). Moreover, CD57 staining also shows an increase in positive cells in T-LGL cases in comparison with normal, reactive, and pathologic marrows with neutropenia. Taken together, these findings indicate immunoperoxidase findings may be a useful tool to identify cases that should proceed to molecular or flow cytometric analysis.

Patient and tumor characteristics of colon cancers with microsatellite instability: a population-based study

Molecular screening for microsatellite instability (MSI) in colon cancers has been proposed to identify individuals with hereditary nonpolyposis colorectal cancer. To date, most reports of MSI in colorectal cancer have been based on studies of clinical case series or high-risk families. We examined the proportion of incident colon cancers in the general population that exhibit MSI by patient and tumor characteristics. We interviewed 201 colon cancer cases ascertained by the New Mexico Tumor Registry in the metropolitan Albuquerque area for demographic information, lifestyle factors, medical history, and family cancer history. Paired normal and tumor tissue specimens were obtained for each case. Three microsatellite markers were used; instability was defined as observed alteration at two or more loci. Overall, 37 of 201 (18%) colon cancers exhibited instability. MSI was more common among cases >70 years (26%) and most common among cases >80 years (38%). MSI was significantly associated with tumors in the proximal colon and with later stage and poor differentiation among cases >70 years. MSI was not associated with a history of polyps. Family history of colorectal cancer was associated with MSI only among cases <50 years. When all factors were analyzed jointly in a regression model, proximal subsite and poor differentiation remained significantly associated with MSI. One patient, whose tumor exhibited MSI, fulfilled the Amsterdam Criteria for hereditary nonpolyposis colorectal cancer. Our study provides a population-based estimate of MSI in colon tumors and a representative estimate of the proportion of colorectal cancer patients in the general population who consent to be interviewed for family cancer history and to have biological samples analyzed.

Association of PML-RAR alpha fusion mRNA type with pretreatment hematologic characteristics but not treatment outcome in acute promyelocytic leukemia: an intergroup molecular study

In each case of acute promyelocytic leukemia (APL) one of three PML-RAR alpha mRNA types is produced, depending on the break/fusion site in the PML gene that is linked to a common RAR alpha gene segment: a short (S)-form type, PML exon 3 RAR alpha exon 3; a long (L)-form type, PML exon 6 RAR alpha exon 3; or a variable (V)-form type, variably deleted PML exon 6 RAR alpha exon 3. We evaluated whether PML-RAR alpha mRNA type is associated with distinct pretreatment clinical characteristics and therapeutic outcome in previously untreated adult APL patients registered to protocol INT 0129 by the Eastern Cooperative Oncology Group, the Southwest Oncology Group, and the Cancer and Leukemia Group B. Of 279 clinically eligible cases, 230 were molecularly evaluable, and of these, 111 were randomized to receive remission induction therapy with all-trans retinoic acid (ATRA) and 119 with conventional chemotherapy. Nine cases not excluded by central pathology review were PML-RAR alpha negative, and notably, none of five of these cases treated with ATRA achieved complete remission (CR). Among 221 PML-RAR alpha-positive cases, there were 82 S-form cases (37%), 121 L-form cases (55%), and 18 V-form cases (8%). Before any antileukemic therapy, the S-form type, compared with the L-form type, was associated with higher values for the white blood cell (WBC) count (median 2,500/microL v 1,600/microL; P = .009), the percentage of blood blasts plus promyelocytes (median 29% v 8.5%; P = .03), and the absolute blood blasts plus promyelocytes (884/microL v 126/microL; P = .019). Also, an increased percentage of S-form versus L-form cases had the M3 variant phenotype, 24% v 12% (P = .036). There were no differences between S-form and L-form cases in either CR rate (79% v 69%; P = .14) or disease free survival distribution (multivariate analysis adjusting for the association of S-form type and higher WBC count; P = .40). We conclude that the S-form type is associated with previously-identified adverse risk WBC parameters but that the identification of the S-form or L-form type of PML-RAR alpha mRNA, per se, does not predict clinical outcome or add to the value of an increased WBC count as a negative prognostic indicator in APL patients.

Usefulness of the dissecting microscope in the surgical management of skin cancers

Dermatopathological examination of excised skin cancers serves the dual purposes of defining the nature of the malignancies and evaluating the resection margins for evidence of tumor involvement. Conventional histological techniques, including horizontal frozen sections as prescribed in Mohs micrographic surgery to evaluate resection margins, can often be tedious and not without many pitfalls. In this study, the use of a stereoscopic dissecting microscope is compared with routine microscopy in the examination of 54 skin specimens resected with the clinical diagnosis of cancer. Our results show that the dissecting microscope is more efficient and as accurate in diagnosing basal and squamous cell carcinomas, and in detecting tumor involvement of resection margins. The ability to visualize marginal surfaces in three dimensions allows for a thorough examination and quick localization and mapping of the involved sites. Tissue artifacts due to fixation, freezing, or sectioning are nonexistent. With the lower cost and ease of operation, we suggest that the dissecting microscope is a more superior instrument. Its usefulness in the surgical management of skin cancers should be emphasized and further validated.