Optimization of Advanced Molecular Genetic Testing Utilization in Hematopathology: A Goldilocks Approach to Bone Marrow Testing

PURPOSE

This study investigated the effectiveness of algorithmic testing in hematopathology at the Brigham and Women's Hospital and Dana-Farber Cancer Institute (DFCI). The algorithm was predicated on test selection after an initial pathologic evaluation to maximize cost-effective testing, especially for expensive molecular and cytogenetic assays.

MATERIALS AND METHODS

Standard ordering protocols (SOPs) for 17 disease categories were developed and encoded in a decision support application. Six months of retrospective data from application beta testing was obtained and compared with actual testing practices during that timeframe. In addition, 2 years of prospective data were also obtained from patients at one community satellite site.

RESULTS

A total of 460 retrospective cases (before introduction of algorithmic testing) and 109 prospective cases (following introduction) were analyzed. In the retrospective data, 61.7% of tests (509 of 825) were concordant with the SOPs while 38.3% (316 of 825) were overordered and 30.8% (227 of 736) of SOP-recommended tests were omitted. In the prospective data, 98.8% of testing was concordant (244 of 247 total tests) with only 1.2% overordered tests (3 of 247) and 7.6% omitted tests (20 of 264 SOP-recommended tests; overall P < .001). The cost of overordered tests before implementing SOP indicates a potential annualized saving of $1,347,520 in US dollars (USD) in overordered testing at Brigham and Women's Hospital/DFCI. Only two of 316 overordered tests (0.6%) returned any additional information, both for extremely rare clinical circumstances.

CONCLUSION

Implementation of SOPs dramatically improved test ordering practices, with a just right number of ancillary tests that minimizes cost and has no significant impact on acquiring key informative test results.

KLRG1 Cell Depletion As A Novel Therapeutic Strategy In Patients With Mature T-cell lymphoma Subtypes

PURPOSE

Develop a novel therapeutic strategy for patients with subtypes of mature T-cell and NK-cell neoplasms.

EXPERIMENTAL DESIGN

Primary specimens, cell lines, patient-derived xenograft models, commercially available and proprietary anti-KLRG1 antibodies were used for screening, target, and functional validation.

RESULTS

Here we demonstrate that surface KLRG1 is highly expressed on tumor cells in subsets of patients with extranodal NK/T-cell lymphoma (ENKTCL), T-prolymphocytic leukemia (T-PLL) and gamma/delta T-cell lymphoma (G/D TCL). The majority of the CD8+/CD57+ or CD3-/CD56+ leukemic cells derived from patients with T- and NK-large granular lymphocytic leukemia (T-LGLL and NK-LGLL) respectively expressed surface KLRG1. The humanized afucosylated anti-KLRG1 monoclonal antibody (mAb208) optimized for mouse in vivo use depleted KLRG1+ TCL cells by mechanisms of ADCC, ADCP and CDC rather than apoptosis. mAb208 induced ADCC and ADCP of T-LGLL patient-derived CD8+/CD57+ cells ex vivo. mAb208 effected ADCC of subsets of healthy donor-derived KLRG1+ NK, CD4+, CD8+ Tem and TemRA cells while sparing KLRG1- naive and CD8+ Tcm cells. Treatment of cell line and TCL patient-derived xenografts with mAb208 or anti-CD47 mAb alone and in combination with the PI3K-δ/γ inhibitor, duvelisib extended survival. The depletion of macrophages in vivo antagonized mAb208 efficacy.

CONCLUSIONS

Our findings suggest the potential benefit of a broader treatment strategy combining therapeutic antibodies with PI3Ki for the treatment of patients with mature T-cell and NK-cell neoplasms.

Cutaneous Manifestations of Myeloid Neoplasms Exhibit Broad and Divergent Morphologic and Immunophenotypic Features but Share Ancestral Clonal Mutations With Bone Marrow

In this study, we performed a comprehensive molecular analysis of paired skin and peripheral blood/bone marrow (BM) samples from 17 patients with cutaneous myeloid or cutaneous histiocytic-dendritic neoplasms. The cutaneous manifestations included 10 patients with cutaneous acute myeloid leukemia (c-AML), 2 patients with full or partial Langerhans cell differentiation, 2 patients with blastic plasmacytoid dendritic cell neoplasms (BPDCN), 1 patient with both Langerhans cell differentiation and BPDCN, and 2 patients with full or partial indeterminate dendritic cell differentiation. Seven of the 10 c-AML patients (70%) exhibited concurrent or subsequent marrow involvement by acute myeloid leukemia, with all 7 cases (100%) demonstrating shared clonal mutations in both the skin and BM. However, clonal relatedness was documented in one additional case that never had any BM involvement. Nevertheless, NPM1 mutations were identified in 7 of the 10 (70%) of these c-AML cases while one had KMT2A rearrangement and one showed inv(16). All 3 patients (100%) with Langerhans cell neoplasms, 2 patients with BPDCN (100%), and one of the 2 patients (50%) with other cutaneous dendritic cell neoplasms also demonstrated shared mutations between the skin and concurrent or subsequent myeloid neoplasms. Both BM and c-AML shared identical founding drivers, with a predominance of NPM1, DNMT3A, and translocations associated with monocytic differentiation, with common cutaneous-only mutations involving genes in the signal transduction and epigenetic pathways. Cutaneous histiocytic-dendritic neoplasms shared founding drivers in ASXL1, TET2, and/or SRSF2. However, in the Langerhans cell histiocytosis or histiocytic sarcoma cases, there exist recurrent secondary RAS pathway hits, whereas cutaneous BPDCN cases exhibit copy number or structural variants. These results enrich and broaden our understanding of clonally related cutaneous manifestations of myeloid neoplasms and further illuminate the highly diverse spectrum of morphologic and immunophenotypic features they exhibit.

A Challenging Diagnosis of Merkel Cell Carcinoma Occurring in the Lymph Nodes and Skin of a Patient with Mantle Cell Lymphoma: A Case Report

Abstract is missing (Short communication)

Ultraviolet radiation shapes dendritic cell leukaemia transformation in the skin

Tumours most often arise from progression of precursor clones within a single anatomical niche. In the bone marrow, clonal progenitors can undergo malignant transformation to acute leukaemia, or differentiate into immune cells that contribute to disease pathology in peripheral tissues^1-4. Outside the marrow, these clones are potentially exposed to a variety of tissue-specific mutational processes, although the consequences of this are unclear. Here we investigate the development of blastic plasmacytoid dendritic cell neoplasm (BPDCN)-an unusual form of acute leukaemia that often presents with malignant cells isolated to the skin⁵. Using tumour phylogenomics and single-cell transcriptomics with genotyping, we find that BPDCN arises from clonal (premalignant) haematopoietic precursors in the bone marrow. We observe that BPDCN skin tumours first develop at sun-exposed anatomical sites and are distinguished by clonally expanded mutations induced by ultraviolet (UV) radiation. A reconstruction of tumour phylogenies reveals that UV damage can precede the acquisition of alterations associated with malignant transformation, implicating sun exposure of plasmacytoid dendritic cells or committed precursors during BPDCN pathogenesis. Functionally, we find that loss-of-function mutations in Tet2, the most common premalignant alteration in BPDCN, confer resistance to UV-induced cell death in plasmacytoid, but not conventional, dendritic cells, suggesting a context-dependent tumour-suppressive role for TET2. These findings demonstrate how tissue-specific environmental exposures at distant anatomical sites can shape the evolution of premalignant clones to disseminated cancer.

Mechanisms of response and resistance to combined decitabine and ipilimumab for advanced myeloid disease

The challenge of eradicating leukemia in patients with acute myelogenous leukemia (AML) after initial cytoreduction has motivated modern efforts to combine synergistic active modalities including immunotherapy. Recently, the ETCTN/CTEP 10026 study tested the combination of the DNA methyltransferase inhibitor decitabine together with the immune checkpoint inhibitor ipilimumab for AML/myelodysplastic syndrome (MDS) either after allogeneic hematopoietic stem cell transplantation (HSCT) or in the HSCT-naïve setting. Integrative transcriptome-based analysis of 304 961 individual marrow-infiltrating cells for 18 of 48 subjects treated on study revealed the strong association of response with a high baseline ratio of T to AML cells. Clinical responses were predominantly driven by decitabine-induced cytoreduction. Evidence of immune activation was only apparent after ipilimumab exposure, which altered CD4+ T-cell gene expression, in line with ongoing T-cell differentiation and increased frequency of marrow-infiltrating regulatory T cells. For post-HSCT samples, relapse could be attributed to insufficient clearing of malignant clones in progenitor cell populations. In contrast to AML/MDS bone marrow, the transcriptomes of leukemia cutis samples from patients with durable remission after ipilimumab monotherapy showed evidence of increased infiltration with antigen-experienced resident memory T cells and higher expression of CTLA-4 and FOXP3. Altogether, activity of combined decitabine and ipilimumab is impacted by cellular expression states within the microenvironmental niche of leukemic cells. The inadequate elimination of leukemic progenitors mandates urgent development of novel approaches for targeting these cell populations to generate long-lasting responses. This trial was registered at www.clinicaltrials.gov as #NCT02890329.

Myeloid sarcoma with NPM1 mutation may be clinically and genetically distinct from AML with NPM1 mutation: a study from the Bone Marrow Pathology Group

Myeloid sarcoma (MS) is currently considered equivalent to de novo acute myeloid leukemia (AML); however, the relationship between these entities is poorly understood. This retrospective multi-institutional cohort study compared 43 MS with NPM1 mutation to 106 AML with NPM1 mutation. Compared to AML, MS had more frequent cytogenetic abnormalities including complex karyotype (p = .009 and p = .007, respectively) and was enriched in mutations of genes involved in histone modification, including ASXL1 (p = .007 and p = .008, respectively). AML harbored a higher average number of gene mutations (p = .002) including more frequent PTPN11 mutations (p < .001) and mutations of DNA-methylating genes including DNMT3A and IDH1 (both p < .001). MS had significantly shorter overall survival (OS) than AML (median OS: 44.9 vs. 93.2 months, respectively, p = .037). MS with NPM1 mutation has a unique genetic landscape, and poorer OS, compared to AML with NPM1 mutation.

Epstein-Barr virus prevalence among subtypes of malignant lymphoma in Rwanda, 2012 to 2018

Few data exist on Epstein-Barr virus (EBV) prevalence across the full spectrum of lymphoma subtypes, particularly in sub-Saharan Africa. The objective of our study was to test the presence of EBV in a nationally representative sample of malignant lymphomas diagnosed in the Butaro Cancer Center of Excellence (BCCOE) in Rwanda. Of 102 Hodgkin (HL) and 378 non-Hodgkin lymphomas (NHL) diagnosed in BCCOE between 2012 and 2018, 52 HL and 207 NHL were successfully tested by EBV-encoding RNA in situ hybridization. EBV prevalence was 54% in HL, being detected in all classical HL subtypes: mixed-cellularity (n = 3/8), nodular-sclerosis (n = 7/17) and lymphocyte-rich (n = 2/3). EBV prevalence was 9% in NHL, being 10% among 158 B-cell NHL, 3% among 35 T-cell NHL and the single NK-cell NHL was EBV-positive. Among B-cell NHL, EBV was present in the majority of Burkitt (n = 8/13), and was also rarely detected in follicular (n = 1/4) and acute B-cell lymphoblastic (n = 1/45) lymphomas. Five of the 45 (11%) diffuse large B-cell lymphomas (DLBCLs) were EBV-positive, including three out of five plasmablastic lymphoma (PBL). Of 39 HL and 163 NHL of known human immunodeficiency virus (HIV) status, 2 (5%) and 14 (9%) were HIV-positive, respectively, of which only four were also EBV-positive (2 PBL, 2 HL). In summary, we report rare regional-level data on the association of EBV with classical HL, Burkitt and DLBCLs, and report sporadic detection in other subtypes possibly related to EBV. Such data inform the burden of disease caused by EBV and can help guide application of future advances in EBV-specific prevention and therapeutics.

Sex-biased ZRSR2 mutations in myeloid malignancies impair plasmacytoid dendritic cell activation and apoptosis

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive leukemia of plasmacytoid dendritic cells (pDCs). BPDCN occurs at least three times more frequently in men than women, but the reasons for this sex bias are unknown. Here, studying genomics of primary BPDCN and modeling disease-associated mutations, we link acquired alterations in RNA splicing to abnormal pDC development and inflammatory response through Toll-like receptors. Loss-of-function mutations in ZRSR2, an X chromosome gene encoding a splicing factor, are enriched in BPDCN and nearly all mutations occur in males. ZRSR2 mutation impairs pDC activation and apoptosis after inflammatory stimuli, associated with intron retention and inability to upregulate the transcription factor IRF7. In vivo, BPDCN-associated mutations promote pDC expansion and signatures of decreased activation. These data support a model in which male-biased mutations in hematopoietic progenitors alter pDC function and confer protection from apoptosis, which may impair immunity and predispose to leukemic transformation.

Cohesin mutations alter DNA damage repair and chromatin structure and create therapeutic vulnerabilities in MDS/AML

The cohesin complex plays an essential role in chromosome maintenance and transcriptional regulation. Recurrent somatic mutations in the cohesin complex are frequent genetic drivers in cancer, including myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). Here, using genetic dependency screens of stromal antigen 2-mutant (STAG2-mutant) AML, we identified DNA damage repair and replication as genetic dependencies in cohesin-mutant cells. We demonstrated increased levels of DNA damage and sensitivity of cohesin-mutant cells to poly(ADP-ribose) polymerase (PARP) inhibition. We developed a mouse model of MDS in which Stag2 mutations arose as clonal secondary lesions in the background of clonal hematopoiesis driven by tet methylcytosine dioxygenase 2 (Tet2) mutations and demonstrated selective depletion of cohesin-mutant cells with PARP inhibition in vivo. Finally, we demonstrated a shift from STAG2- to STAG1-containing cohesin complexes in cohesin-mutant cells, which was associated with longer DNA loop extrusion, more intermixing of chromatin compartments, and increased interaction with PARP and replication protein A complex. Our findings inform the biology and therapeutic opportunities for cohesin-mutant malignancies.

Imaging of IgG4-Related Disease in the Head and Neck: A Systematic Review, Case Series, and Pathophysiology Update

This systematic review aims to clarify and comprehensively detail the sometimes variable published imaging features as well as the pathogenesis, clinical diagnostic criteria, and treatment options of IgG4-Related Diseases (IgG4-RD) in the head and neck to aid the radiologist in diagnosing relapse and new sites of disease. A literature search in PubMed and EMBASE for reported cases of IgG4-RD was performed in December 2019. Case reports or series of IgG4-RD in the head and neck in adults that included sufficient imaging and pathology findings were included. This yielded 50 reports. IgG4-RD locations included the orbits, thyroid, pituitary gland, paranasal sinuses, salivary and parotid glands, larynx, pharynx, cervical lymph nodes, meninges, and skull base. Most lesions demonstrated non-specific homogenous CT attenuation, diffuse enhancement, isointense/low T2 signal intensity, and low T1 signal intensity. 6 cases from our institution followed previously reported imaging patterns.

LIM domain only 2 (LMO2) expression distinguishes T-lymphoblastic leukemia/lymphoma from indolent T-lymphoblastic proliferations

AIMS

An indolent T-lymphoblastic proliferation (iT-LBP) is a benign, reactive expansion of immature terminal deoxynucleotidyl transferase (TdT)-positive T cells found in extrathymic tissues. iT-LBP can be challenging to distinguish from malignant processes, specifically T-lymphoblastic lymphoma (T-LBL), given the overlapping clinical and histological features. Recently, it has been shown that LIM domain only 2 (LMO2) is overexpressed in T-LBL but not in reactive immature TdT+ T cells in the thymus. On the basis of these findings, the aim of this study was to investigate the expression of LMO2 by using immunohistochemistry and its role in differentiating iT-LBPs from T-LBLs.

METHODS AND RESULTS

We retrospectively identified cases of iT-LBP and T-LBL from the pathology archives of four institutions. Seven iT-LBP cases (including five new cases that have not been reported in the literature) and 13 T-LBL cases were analysed. Clinical, morphological, immunophenotypic and molecular data were analysed. Immunohistochemical staining with LMO2 was performed on all iT-LBP and T-LBL cases. A review of five new iT-LBP cases showed similar morphological, immunophenotypic and molecular features to those of previously reported cases. All iT-LBP cases were negative for LMO2 (0/7), whereas 92% of T-LBL cases (12/13) expressed LMO2; the sensitivity was 92% (confidence interval 64-100%) and the specificity was 100% (confidence interval 59-100%).

CONCLUSION

We confirm previously published findings that iT-LBP cases show highly overlapping morphological and immunophenotypic features with T-LBL. Importantly, LMO2 expression is a sensitive and specific marker with which to rule out iT-LBP.

Genomic Profiling of Smoldering Multiple Myeloma Identifies Patients at a High Risk of Disease Progression

PURPOSE

Smoldering multiple myeloma (SMM) is a precursor condition of multiple myeloma (MM) with a 10% annual risk of progression. Various prognostic models exist for risk stratification; however, those are based on solely clinical metrics. The discovery of genomic alterations that underlie disease progression to MM could improve current risk models.

METHODS

We used next-generation sequencing to study 214 patients with SMM. We performed whole-exome sequencing on 166 tumors, including 5 with serial samples, and deep targeted sequencing on 48 tumors.

RESULTS

We observed that most of the genetic alterations necessary for progression have already been acquired by the diagnosis of SMM. Particularly, we found that alterations of the mitogen-activated protein kinase pathway (KRAS and NRAS single nucleotide variants [SNVs]), the DNA repair pathway (deletion 17p, TP53, and ATM SNVs), and MYC (translocations or copy number variations) were all independent risk factors of progression after accounting for clinical risk staging. We validated these findings in an external SMM cohort by showing that patients who have any of these three features have a higher risk of progressing to MM. Moreover, APOBEC associated mutations were enriched in patients who progressed and were associated with a shorter time to progression in our cohort.

CONCLUSION

SMM is a genetically mature entity whereby most driver genetic alterations have already occurred, which suggests the existence of a right-skewed model of genetic evolution from monoclonal gammopathy of undetermined significance to MM. We identified and externally validated genomic predictors of progression that could distinguish patients at high risk of progression to MM and, thus, improve on the precision of current clinical models.

Why "good enough" is not good enough: scientific data, not supply chain deficiencies, should be driving Centers for Disease Control and Prevention recommendations

Obstetricians and clinicians previously requested clarification from the Centers for Disease Control and Prevention on the need for full personal protective equipment including N95 respirators during the second stage of labor. The Centers for Disease Control and Prevention responded with new guidance excluding the second stage of labor from its list of aerosol-generating procedures based on research from which experience on labor and delivery units was notably absent. Additional literature that explores other modes of aerosol generation, such as coughing, vomiting, passing flatus, and loud vocalization, all of which are prevalent during the labor course, was notably omitted.

It is clear that the Centers for Disease Control and Prevention based their guidance not from the application of scientific principles but from pragmatism owing to the lack of equipment, and our colleagues were urged to follow suit. If we replace recommendations based on scientific principles with recommendations based on supply chain deficiencies, we become complacent with that which is “good enough under the circumstances.” This is a dangerous precedent on which to base our professional society guidelines. We should continue to address these inadequate responses even as Centers for Disease Control and Prevention guidelines evolve and the pandemic winds down. We will certainly face similar conflict again, whether during a fall resurgence of the current pandemic or a future infectious disease outbreak.

Detection of the KITD816V mutation in myelodysplastic and/or myeloproliferative neoplasms and acute myeloid leukemia with myelodysplasia-related changes predicts concurrent systemic mastocytosis

Greater than 90% of cases of systemic mastocytosis (SM) harbor pathogenic KIT mutations, particularly KIT^D816V. Prognostically-significant pathogenic KIT mutations also occur in 30-40% of core binding factor-associated acute myeloid leukemia (CBF-AML), but are uncommonly associated with concurrent SM. By comparison, the occurrence of SM in other myeloid neoplasms bearing pathogenic KIT mutations, particularly those with a chronic course, is poorly understood. Review of clinical next-generation sequencing (NGS) performed at our institutions in patients with known or suspected hematologic malignancies over an 8-year period revealed 64 patients with both a pathogenic KIT mutation detected at one or more timepoints and available bone marrow biopsy materials. Patients with KIT^D816V-mutated myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), or overlap MDS/MPN (n = 22) accounted for approximately one-third of our cohort (34%). Comprehensive morphologic and immunophenotypic characterization revealed that nearly all cases (n = 20, 91%) exhibited concurrent SM. In contrast, of the 18 patients (28%) with AML and KIT^D816V, only eight (44%) showed evidence of SM at any point in their disease course (p = 0.0021); of these eight, the AML component was characterized as AML with myelodysplasia-related changes (AML-MRC) in all but one instance (n = 7, 87%). Twelve patients (19%) had pathogenic KIT mutations other than p.D816V, all in the setting of AML (CFB-AML, n = 7; AML, not otherwise specified, n = 2; AML-MRC, n = 1; acute promyelocytic leukemia, n = 1); only two of these patients (17%), both with CBF-AML, exhibited concurrent SM. The remaining 12 patients (19%) had SM without evidence of an associated hematological neoplasm (AHN). For nearly one-third of the 30 SM-AHN patients in our cohort (n = 9, 30%), the SM component of their disease was not initially clinicopathologically recognized. We propose that identification of the KIT^D816V mutation in patients diagnosed with MDS, MPN, MDS/MPN, or AML-MRC should trigger reflex testing for SM.

Proapoptotic protein BIM as a novel prognostic marker in mantle cell lymphoma

Mantle cell lymphoma (MCL) is an aggressive B-cell lymphoma. Numerous studies have demonstrated many genetic aberrations in MCL in addition to the characteristic t(11:14), including frequent biallelic deletions of Bim, a proapoptotic member of the BCL-2 family. In mice, Bim deletion coupled with cyclin D1 overexpression generates pathologic and molecular features of human MCL. Since the regulation of apoptosis is crucial in MCL pathogenesis, we hypothesize that BIM expression may be associated with tumor cell survival. Clinical data and tissue from 100 nodal MCL cases between 1988 and 2009 were collected from three large academic medical centers. The average patient age of our MCL cohort was 65.5 years old (range, 42-97) with a 2:1 male to female ratio. Immunohistochemistry was performed with a validated anti-BIM antibody. Patients were separated into low and high BIM-expressing categories with a cutoff of 80%. As expected for a proapoptotic tumor suppressor, patients with high BIM expression were less likely to have progressive disease and more likely to have a complete response (P = .022). In addition, high BIM-expressing MCL tumors revealed a trend toward increased overall survival with this trend persisting in sub-analysis of Ann Arbor stages III and IV. No correlation between BIM expression, Ki-67 index, and MIPI score was observed, suggesting a role for BIM as a novel independent prognostic factor. While BIM is only one member of a complex family of apoptosis-regulating proteins, these findings may yield clinically relevant information for the prognosis and therapeutic susceptibility of MCL.

Targeted inhibition of CD47-SIRPα requires Fc-FcγR interactions to maximize activity in T-cell lymphomas

Antibodies that bind CD47 on tumor cells and prevent interaction with SIRPα on phagocytes are active against multiple cancer types including T-cell lymphoma (TCL). Here we demonstrate that surface CD47 is heterogeneously expressed across primary TCLs, whereas major histocompatibility complex (MHC) class I, which can also suppress phagocytosis, is ubiquitous. Multiple monoclonal antibodies (mAbs) that block CD47-SIRPα interaction promoted phagocytosis of TCL cells, which was enhanced by cotreatment with antibodies targeting MHC class I. Expression levels of surface CD47 and genes that modulate CD47 pyroglutamation did not correlate with the extent of phagocytosis induced by CD47 blockade in TCL lines. In vivo treatment of multiple human TCL patient-derived xenografts or an immunocompetent murine TCL model with a short course of anti-CD47 mAb markedly reduced lymphoma burden and extended survival. Depletion of macrophages reduced efficacy in vivo, whereas depletion of neutrophils had no effect. F(ab')2-only fragments of anti-CD47 antibodies failed to induce phagocytosis by human macrophages, indicating a requirement for Fc-Fcγ receptor interactions. In contrast, F(ab')2-only fragments increased phagocytosis by murine macrophages independent of SLAMF7-Mac-1 interaction. Full-length anti-CD47 mAbs also induced phagocytosis by Fcγ receptor-deficient murine macrophages. An immunoglobulin G1 anti-CD47 mAb induced phagocytosis and natural killer cell-mediated cytotoxicity of TCL cells that was augmented by cotreatment with mogamulizumab, an anti-CCR4 mAb, or a mAb blocking MHC class I. These studies help explain the disparate activity of monotherapy with agents that block CD47 in murine models compared with patients. They also have direct translational implications for the deployment of anti-CD47 mAbs alone or in combination.

The effect of placental location in cases of placenta accreta spectrum

BACKGROUND

Placenta accreta spectrum affects approximately 3 in 1000 pregnancies. There is a paucity of data evaluating the effect of placental location on diagnosis, risk factors, and resultant outcomes in cases of placenta accreta spectrum.

OBJECTIVE

We analyzed placenta accreta spectrum cases to assess whether risk factors or maternal outcomes varied based on placental location.

MATERIALS AND METHODS

We performed a retrospective chart review of pathology-confirmed cases of placenta accreta spectrum from patients delivering at 2 large urban hospitals in the same healthcare system from 2007 to 2017. Placental location was defined by ultrasound images and confirmed by pathology reports. Location was categorized as anterior, posterior, or anterior/posterior for those with placental location at both sites. Fisher exact tests and analysis of variance were used to examine associations with measures of diagnosis, risk factors, and maternal outcomes.

RESULTS

A total of 86 pathology-confirmed placenta accreta spectrum cases were reviewed. The distribution of placental location on ultrasound was as follows: 19% posterior, 59% anterior, and 22% anterior/posterior. We found that prior cesarean delivery was lower with posterior placenta accreta spectrum (63% vs 94% vs 84% in the anterior and anterior/posterior groups respectively; (P = .007); however, in vitro fertilization rates were significantly higher (38% vs 2% vs 5% in the anterior and anterior/posterior groups respectively; P = .001). There was also lower incidence of percreta with posterior placenta accreta spectrum compared to the anterior and anterior/posterior groups (19% vs 47% vs 58% respectively; P = .055). Posterior cases were less likely to have placenta accreta spectrum suspected prenatally (50%) compared to anterior (80%) and anterior/posterior (89%) cases (P = .019). Despite late diagnosis, ureteral injury was the only surgical complication that was more common in patients with posterior placenta accreta spectrum (13% vs 0% vs 5% for anterior and anterior/posterior groups respectively; P = .037).

CONCLUSION

Placenta accreta spectrum with posterior placental location is associated with delayed diagnosis, surgical complications, assisted reproductive technology, and lower numbers of prior cesarean deliveries relative to anterior location. These differences in outcomes and risk factors based on placental location may allow for heightened clinical awareness, and improved diagnosis and management.

Variable loss of CD30 expression by immunohistochemistry in recurrent cutaneous CD30+ lymphoid neoplasms treated with brentuximab vedotin

AIMS

Brentuximab vedotin is a monoclonal anti-CD30 antibody-drug conjugate that has been used to treat a variety of CD30+ neoplasms. The phenomenon of antigen loss has been observed in patients treated with the anti-CD20 antibody rituximab. This study seeks to assess for antigen loss in the setting of recurrent CD30+ neoplasms treated with brentuximab vedotin.

METHODS

We report nine cases of persistent/recurrent cutaneous CD30+ lymphoid neoplasms that demonstrated variable CD30 expression after treatment with brentuximab vedotin. Cases include MF (n = 6), cutaneous T-cell lymphoma, not otherwise specified (n = 1), and anaplastic large cell lymphoma (ALCL), both primary (n = 1) and systemic (n = 1).

RESULTS

Immunohistochemical staining revealed decreased CD30 expression following brentuximab vedotin therapy in seven of nine cases. In these seven cases, the pre-treatment percent of tumor cells staining for CD30 ranged from 10% to 100% (mean 50.0%, SD 27.8%), compared to 5% to 50% (mean 14.5%, SD 14.8%, P = 0.003) at recurrence.

CONCLUSIONS

This case series highlights the finding that CD30 positivity can be variable in recurrences after treatment with anti-CD30 antibodies. This serves to raise awareness of the phenomenon of antigen loss after treatment with brentuximab vedotin and underscores the utility of performing multiple biopsies and/or employing molecular diagnostic techniques in patients with recurrent/persistent disease.

Genetic Testing in the Diagnosis and Biology of Myeloid Neoplasms (Excluding Acute Leukemias)

OBJECTIVES

The 2017 Workshop of the Society for Hematopathology/European Association for Haematopathology reviewed the role of genetic testing in the diagnosis of hematopoietic neoplasms, including non-acute leukemia myeloid malignancies.

METHODS

The workshop panel assigned 98 submitted cases to the category of non-acute leukemia myeloid neoplasms, of which 13 were selected for oral presentation.

RESULTS

Data from both conventional karyotyping and genetic sequencing had important impact on diagnosis, classification, and prognostication. However, some cases had genetic results that appeared discordant from the morphology and/or clinical features. Thus, the workshop underscored the need for careful management of genetic data by the pathologist and clinician, in the context of other findings.

CONCLUSIONS

The workshop cases highlighted the significance of genetic aberrations in the diagnosis and treatment of non-acute leukemia myeloid neoplasms. Many genetic data have already been incorporated in the most recent World Health Organization classification, and undoubtedly they will factor increasingly in future classifications.

Mechanisms of Lymphoma Clearance Induced by High-Dose Alkylating Agents

The extraordinary activity of high-dose cyclophosphamide against some high-grade lymphomas was described nearly 60 years ago. Here we address mechanisms that mediate cyclophosphamide activity in bona fide human double-hit lymphoma. We show that antibody resistance within the bone marrow (BM) is not present upon early engraftment but develops during lymphoma progression. This resistance required a high tumor:macrophage ratio, was recapitulated in spleen by partial macrophage depletion, and was overcome by multiple, high-dose alkylating agents. Cyclophosphamide induced endoplasmic reticulum (ER) stress in BM-resident lymphoma cells in vivo that resulted in ATF4-mediated paracrine secretion of VEGFA, massive macrophage infiltration, and clearance of alemtuzumab-opsonized cells. BM macrophages isolated after cyclophosphamide treatment had increased phagocytic capacity that was reversed by VEGFA blockade or SYK inhibition. Single-cell RNA sequencing of these macrophages identified a "super-phagocytic" subset that expressed CD36/FCGR4. Together, these findings define a novel mechanism through which high-dose alkylating agents promote macrophage-dependent lymphoma clearance. SIGNIFICANCE: mAbs are effective against only a small subset of cancers. Herein, we recapitulate compartment-specific antibody resistance and define an ER stress-dependent mechanism induced by high-dose alkylating agents that promotes phagocytosis of opsonized tumor cells. This approach induces synergistic effects with mAbs and merits testing across additional tumor types.See related commentary by Duval and De Palma, p. 834.This article is highlighted in the In This Issue feature, p. 813.

Intergenerational epigenetic inheritance of cancer susceptibility in mammals

Susceptibility to cancer is heritable, but much of this heritability remains unexplained. Some 'missing' heritability may be mediated by epigenetic changes in the parental germ line that do not involve transmission of genetic variants from parent to offspring. We report that deletion of the chromatin regulator Kdm6a (Utx) in the paternal germ line results in elevated tumor incidence in genetically wild type mice. This effect increases following passage through two successive generations of Kdm6a male germline deletion, but is lost following passage through a wild type germ line. The H3K27me3 mark is redistributed in sperm of Kdm6a mutants, and we define approximately 200 H3K27me3-marked regions that exhibit increased DNA methylation, both in sperm of Kdm6a mutants and in somatic tissue of progeny. Hypermethylated regions in enhancers may alter regulation of genes involved in cancer initiation or progression. Epigenetic changes in male gametes may therefore impact cancer susceptibility in adult offspring.

NK-Cell Enteropathy and Similar Indolent Lymphoproliferative Disorders: A Case Series With Literature Review

Objectives

We report four new cases of natural killer-cell enteropathy (NKCE) and similar lymphoproliferative disorders (LPDs), as well as review the literature concerning indolent natural killer (NK)-cell LPDs of the gastrointestinal tract.

Methods

Pathologic and clinical data were obtained from institutional/referral records.

Results

Patient 1 (45-year-old man) had anemia; a small intestinal lesion was endoscopically biopsied. Patient 2 (65-year-old woman) had biliary colic, treated with cholecystectomy. Patient 3 (62-year-old man) had a small colonic polyp, biopsied on routine colonoscopy. Patient 4 (68-year-old man) had presumed Crohn disease; multiple biopsies were performed over more than 10 years. Diagnostic specimens showed atypical infiltrates of Epstein-Barr virus-negative lymphocytes with immunophenotypes suggestive of NK cells. In all cases, there was distortion of glandular architecture but no marked intraepithelial lymphocytosis or necrosis. The patients did not receive therapy for lymphoma and were well on follow-up.

Conclusions

These cases support the indolent nature of NKCE and similar LPDs, and they indicate that involvement outside the alimentary canal may occur.

Genomic Analyses Identify Recurrent Alterations in Immune Evasion Genes in Diffuse Large B-Cell Lymphoma, Leg Type

Cutaneous diffuse large B-cell lymphomas (DLBCLs) are aggressive lymphomas with a poor prognosis. To elucidate their genetic bases, we analyzed exome sequencing of 37 cutaneous DLBCLs, including 31 DLBCLs, leg type (DLBCL-LT) and 6 cutaneous DLBCLs-not otherwise specified (DLBCL-NOS). As reported previously, 77% of DLBCL-LT harbor NF-κB-activating MYD88 mutations. In nearly all MYD88-wild-type DLBCL-LT, we found cancer-promoting mutations that either activate the NF-κB pathway through alternative genes (NFKBIE or REL) or activate other canonical cancer pathways (BRAF, MED12, PIK3R1, and STAT3). After NF-κB, the second most commonly mutated pathway putatively enables immune evasion via mutations predicted to downregulate antigen processing (B2M, CIITA, HLA) or T-cell co-stimulation (CD58). DLBCL-LT have little genetic overlap with the genetically heterogeneous DLBCL-NOS. Instead, they resemble primary central nervous system and testicular large B-cell lymphomas (primary central nervous system lymphomas and primary testicular lymphomas). Like primary central nervous system lymphomas/primary testicular lymphomas, 40% of DLBCL-LT (vs. 0% of DLBCLs-not otherwise specified) harbored PDL1/PDL2 translocations, which lead to overexpression of PD-L1 or PD-L2 in 50% of the cases. Collectively, these data broaden our understanding of cutaneous DLBCLs and suggest novel therapeutic approaches (e.g., BRAF or PI3K inhibitors). Additionally, they suggest novel treatment paradigms, wherein DLBCL-LT can be targeted with strategies (e.g., immune checkpoint blockers) currently being developed for genomically similar primary central nervous system lymphomas/primary testicular lymphomas.

Multiplex CRISPR/Cas9-Based Genome Editing in Human Hematopoietic Stem Cells Models Clonal Hematopoiesis and Myeloid Neoplasia

Hematologic malignancies are driven by combinations of genetic lesions that have been difficult to model in human cells. We used CRISPR/Cas9 genome engineering of primary adult and umbilical cord blood CD34⁺ human hematopoietic stem and progenitor cells (HSPCs), the cells of origin for myeloid pre-malignant and malignant diseases, followed by transplantation into immunodeficient mice to generate genetic models of clonal hematopoiesis and neoplasia. Human hematopoietic cells bearing mutations in combinations of genes, including cohesin complex genes, observed in myeloid malignancies generated immunophenotypically defined neoplastic clones capable of long-term, multi-lineage reconstitution and serial transplantation. Employing these models to investigate therapeutic efficacy, we found that TET2 and cohesin-mutated hematopoietic cells were sensitive to azacitidine treatment. These findings demonstrate the potential for generating genetically defined models of human myeloid diseases, and they are suitable for examining the biological consequences of somatic mutations and the testing of therapeutic agents.

Metabolic costs imposed by hydrostatic pressure constrain bathymetric range in the lithodid crab Lithodes maja

The changing climate is shifting the distributions of marine species, yet the potential for shifts in depth distributions is virtually unexplored. Hydrostatic pressure is proposed to contribute to a physiological bottleneck constraining depth range extension in shallow-water taxa. However, bathymetric limitation by hydrostatic pressure remains undemonstrated, and the mechanism limiting hyperbaric tolerance remains hypothetical. Here, we assess the effects of hydrostatic pressure in the lithodid crab Lithodes maja (bathymetric range 4-790 m depth, approximately equivalent to 0.1 to 7.9 MPa hydrostatic pressure). Heart rate decreased with increasing hydrostatic pressure, and was significantly lower at ≥10.0 MPa than at 0.1 MPa. Oxygen consumption increased with increasing hydrostatic pressure to 12.5 MPa, before decreasing as hydrostatic pressure increased to 20.0 MPa; oxygen consumption was significantly higher at 7.5-17.5 MPa than at 0.1 MPa. Increases in expression of genes associated with neurotransmission, metabolism and stress were observed between 7.5 and 12.5 MPa. We suggest that hyperbaric tolerance in Lmaja may be oxygen-limited by hyperbaric effects on heart rate and metabolic rate, but that Lmaja's bathymetric range is limited by metabolic costs imposed by the effects of high hydrostatic pressure. These results advocate including hydrostatic pressure in a complex model of environmental tolerance, where energy limitation constrains biogeographic range, and facilitate the incorporation of hydrostatic pressure into the broader metabolic framework for ecology and evolution. Such an approach is crucial for accurately projecting biogeographic responses to changing climate, and for understanding the ecology and evolution of life at depth.

Flow cytometric minimal residual disease assessment of peripheral blood in acute lymphoblastic leukaemia patients has potential for early detection of relapsed extramedullary disease

OBJECTIVES

To evaluate peripheral blood (PB) for minimal residual disease (MRD) assessment in adults with acute lymphoblastic leukaemia (ALL).

METHODS

We analysed 76 matched bone marrow (BM) aspirate and PB specimens independently for the presence of ALL MRD by six-colour flow cytometry (FC).

RESULTS

The overall rate of BM MRD-positivity was 24% (18/76) and PB was also MRD-positive in 22% (4/18) of BM-positive cases. We identified two cases with evidence of leukaemic cells in PB at the time of the extramedullary relapse that were interpreted as MRD-negative in BM.

CONCLUSIONS

The use of PB MRD as a non-invasive method for monitoring of systemic relapse may have added clinical and diagnostic value in patients with high risk of extramedullary disease.

Lymphoma and Pathology in Sub-Saharan Africa: Current Approaches and Future Directions

The care of patients with lymphoma relies heavily on accurate tissue diagnosis and classification. In sub-Saharan Africa, where lymphoma burden is increasing because of population growth, aging, and continued epidemic levels of human immunodeficiency virus infection, diagnostic pathology services are limited. This article summarizes lymphoma epidemiology, current diagnostic capacity, and obstacles and opportunities for improving practice in the region.

IgM myeloma: A multicenter retrospective study of 134 patients

IgM myeloma is a rare hematologic malignancy for which the clinicopathological features and patient outcomes have not been extensively studied. We carried out a multicenter retrospective study in patients with diagnosis of IgM myeloma defined by >10% marrow involvement by monoclonal plasma cells, presence of an IgM monoclonal paraproteinemia of any size, and anemia, renal dysfunction, hypercalcemia, lytic lesions and/or t(11;14) identified by FISH. A total of 134 patients from 20 centers were included in this analysis. The median age at diagnosis was 65.5 years with a male predominance (68%). Anemia, renal dysfunction, elevated calcium and skeletal lytic lesions were found in 37, 43, 19, and 70%, respectively. The median serum IgM level was 2,895 mg dL^-1 with 19% of patients presenting with levels >6,000 mg dL^-1 . International Staging System (ISS) stages 1, 2, and 3 were seen in 40 (33%), 54 (44%), and 29 (24%) of patients, respectively. The malignant cells expressed CD20 (58%) and cyclin D1 (67%), and t(11;14) was the most common cytogenetic finding (39%). The median overall survival (OS) was 61 months. Higher ISS score was associated with worse survival (P = 0.02). Patients with IgM myeloma present with similar characteristics and outcomes as patients with more common myeloma subtypes.

T-cell transcription factor GATA-3 is an immunophenotypic marker of acute leukemias with T-cell differentiation

T-cell transcription factor GATA-3, known to play a role in early T-cell development and in the development of T-cell neoplasms, is expressed at high levels in fetal and adult thymus, as well as in acute leukemias with T-cell differentiation, including T-lymphoblastic leukemia/lymphoma (22/22 cases), early T-cell precursor lymphoblastic leukemia (11/11 cases), and mixed-phenotype acute leukemia, T/myeloid (4/5 cases), but only rarely in acute myeloid leukemia/myeloid sarcoma (1/36 cases), and not in B-lymphoblastic leukemia (0/16 cases). In contrast, T-bet, the other T-cell transcription factor that controls Th1/Th2 T-cell fate, is not expressed to any significant extent in immature thymocytes or in cases of T-lymphoblastic leukemia or acute myeloid leukemia/myeloid sarcoma, but is expressed in most cases (15/16) of B-lymphoblastic leukemia and in mixed-phenotype acute leukemia, B/myeloid. GATA-3-positive acute leukemias with T-cell differentiation were also found to express proto-oncogene C-MYC, in an average of 52% of neoplastic cells, which, along with GATA-3, may contribute to leukemogenesis, as suggested by transgenic mouse models. We conclude that GATA-3 is a sensitive and specific marker for the diagnosis of acute leukemias with T-cell differentiation and may be a useful addition to the panel of immunophenotypic markers for the diagnostic evaluation of acute leukemias.

Morphological and immunophenotypical features of hairy cell leukaemia involving lymph nodes and extranodal tissues

AIMS

Hairy cell leukaemia (HCL) is a rare B cell neoplasm that mainly affects bone marrow (BM), peripheral blood (PB) and spleen. Involvement of lymph nodes and extranodal structures is considered infrequent. Herein we describe our institutional experience of nodal (n = 10) and extranodal (n = 3) HCL during a 30-year period.

METHODS AND RESULTS

Ten patients had prior evidence of HCL within the BM or PB at a median 35.8 months before nodal/extranodal diagnosis (range: <1-175 months), and HCL was diagnosed concurrently within the bone marrow of one additional patient. Nodal involvement showed distinct architectural patterns, including diffuse (62% of cases), sinusoidal (25%) and nodular (13%). Extranodal involvement was characterized as diffuse infiltration through underlying structures in all cases. Morphological features ranged from classic 'fried-egg' cytology to a plasmacytoid appearance. Nodal/extranodal disease showed an overlapping immunophenotypical profile with other small B cell lymphomas, including expression of cyclin D1 (70%), CD43 (55%), CD10 (38%) and CD5 (8%). Rates of both CD43 and CD10 reactivity were higher than described previously in leukaemic HCL, suggesting that expression may be enriched in cases with extramedullary extension.

CONCLUSIONS

Although uncommon, HCL should be considered in the differential diagnosis of small B cell neoplasms involving nodal/extranodal sites, given the therapeutic implications. In particular, recent discoveries including detection of the BRAF^V600E mutation in nearly all cases of HCL and the availability of an antibody to CD103 for use in paraffin-embedded tissues will facilitate the distinction of HCL from other small B cell lymphomas in the nodal/extranodal setting.

Cost-effective approach to the diagnostic workup of B cell lymphoproliferative disorders via optimal integration of flow cytometric data

INTRODUCTION

The workup of lymphoproliferative disorders (LPDs) involves the combined use of flow cytometry (FC) and immunohistochemistry (IHC). This often results in duplicate immunophenotypic testing and adds costs that may not be eligible for reimbursement based on the Medicare National Correct Coding Initiative. We aimed to establish a cost-effective diagnostic algorithm based on initial FC categorization to reduce repetitive immunophenotyping.

METHODS

We retrospectively reviewed 242 cases of suspected LPDs with concurrent FC and IHC testing over a 12-month period. We correlated FC with surgical diagnoses and evaluated the frequency of repeat IHC testing.

RESULTS

Repetitive immunophenotyping was common; overall, 85% of cases had at least one marker repeated. Concordant cases were significantly less likely to have markers repeated than discordant cases. Of concordant B cell malignancies, 57% represented recurrent disease; however, repeat marker usage was not decreased as compared to new diagnoses. The most frequently repeated markers were CD3, CD5, CD10, and CD20.

CONCLUSIONS

We propose that in concordant cases, CD5 and CD10 should not be repeated by IHC; this would decrease the use of these markers by 80% and 76%, respectively. We developed an algorithmic approach to IHC usage that has improved incorporation of FC data at our institution and may reduce healthcare costs.

Clonal Hematopoiesis Associated With Adverse Outcomes After Autologous Stem-Cell Transplantation for Lymphoma

Purpose Clonal hematopoiesis of indeterminate potential (CHIP) is an age-related condition characterized by somatic mutations in the blood of otherwise healthy adults. We hypothesized that in patients undergoing autologous stem-cell transplantation (ASCT) for lymphoma, CHIP at the time of ASCT would be associated with an increased risk of myelodysplastic syndrome and acute myeloid leukemia, collectively termed therapy-related myeloid neoplasm (TMN), and other adverse outcomes. Methods We performed whole-exome sequencing on pre- and post-ASCT samples from 12 patients who developed TMN after autologous transplantation for Hodgkin lymphoma or non-Hodgkin lymphoma and targeted sequencing on cryopreserved aliquots of autologous stem-cell products from 401 patients who underwent ASCT for non-Hodgkin lymphoma between 2003 and 2010. We assessed the effect of CHIP at the time of ASCT on subsequent outcomes, including TMN, cause-specific mortality, and overall survival. Results For six of 12 patients in the exome sequencing cohort, mutations found in the TMN specimen were also detectable in the pre-ASCT specimen. In the targeted sequencing cohort, 120 patients (29.9%) had CHIP at the time of ASCT, which was associated with an increased rate of TMN (10-year cumulative incidence, 14.1% v 4.3% for those with and without CHIP, respectively; P = .002). Patients with CHIP had significantly inferior overall survival compared with those without CHIP (10-year overall survival, 30.4% v 60.9%, respectively; P < .001), including increased risk of death from TMN and cardiovascular disease. Conclusion In patients undergoing ASCT for lymphoma, CHIP at the time of transplantation is associated with inferior survival and increased risk of TMN.

Blastic Plasmacytoid Dendritic Cell Neoplasm Is Dependent on BCL2 and Sensitive to Venetoclax

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive hematologic malignancy with dismal outcomes for which no standard therapy exists. We found that primary BPDCN cells were dependent on the antiapoptotic protein BCL2 and were uniformly sensitive to the BCL2 inhibitor venetoclax, as measured by direct cytotoxicity, apoptosis assays, and dynamic BH3 profiling. Animals bearing BPDCN patient-derived xenografts had disease responses and improved survival after venetoclax treatment in vivo Finally, we report on 2 patients with relapsed/refractory BPDCN who received venetoclax off-label and experienced significant disease responses. We propose that venetoclax or other BCL2 inhibitors undergo expedited clinical evaluation in BPDCN, alone or in combination with other therapies. In addition, these data illustrate an example of precision medicine to predict treatment response using ex vivo functional assessment of primary tumor tissue, without requiring a genetic biomarker.

SIGNIFICANCE

Therapy for BPDCN is inadequate, and survival in patients with the disease is poor. We used primary tumor cell functional profiling to predict BCL2 antagonist sensitivity as a common feature of BPDCN, and demonstrated in vivo clinical activity of venetoclax in patient-derived xenografts and in 2 patients with relapsed chemotherapy-refractory disease. Cancer Discov; 7(2); 156-64. ©2016 AACR.This article is highlighted in the In This Issue feature, p. 115.

Antagonizing Integrin β3 Increases Immunosuppression in Cancer

Integrin β3 is critical for tumor invasion, neoangiogenesis, and inflammation, making it a promising cancer target. However, preclinical and clinical data of integrin β3 antagonists have demonstrated no benefit or worse outcomes. We hypothesized that integrin β3 could affect tumor immunity and evaluated tumors in mice with deletion of integrin β3 in macrophage lineage cells (β3KOM). β3KOM mice had increased melanoma and breast cancer growth with increased tumor-promoting M2 macrophages and decreased CD8(+) T cells. Integrin β3 antagonist, cilengitide, also enhanced tumor growth and increased M2 function. We uncovered a negative feedback loop in M2 myeloid cells, wherein integrin β3 signaling favored STAT1 activation, an M1-polarizing signal, and suppressed M2-polarizing STAT6 activation. Finally, disruption of CD8(+) T cells, macrophages, or macrophage integrin β3 signaling blocked the tumor-promoting effects of integrin β3 antagonism. These results suggest that effects of integrin β3 therapies on immune cells should be considered to improve outcomes. Cancer Res; 76(12); 3484-95. ©2016 AACR.

Myeloid neoplasm demonstrating a STAT5B-RARA rearrangement and genetic alterations associated with all-trans retinoic acid resistance identified by a custom next-generation sequencing assay

We describe the case of a patient presenting with several weeks of symptoms related to pancytopenia associated with a maturation arrest at the late promyelocyte/early myelocyte stage of granulocyte differentiation. A diagnosis of acute promyelocytic leukemia was considered, but the morphologic features were atypical for this entity and conventional tests for the presence of a PML-RARA fusion gene were negative. Additional analysis using a custom next-generation sequencing assay revealed a rearrangement producing a STAT5B-RARA fusion gene, which was confirmed by reverse transcription polymerase chain reaction (RT-PCR) and supplementary cytogenetic studies, allowing the diagnosis of a morphologically atypical form of acute promyelocytic leukemia to be made. Analysis of the sequencing data permitted characterization of both chromosomal breakpoints and revealed two additional alterations, a small deletion in RARA exon 9 and a RARA R276W substitution, that have been linked to resistance to all-trans retinoic acid. This case highlights how next-generation sequencing can augment currently standard testing to establish diagnoses in difficult cases, and in doing so help guide selection of therapy.

The Public Repository of Xenografts Enables Discovery and Randomized Phase II-like Trials in Mice

More than 90% of drugs with preclinical activity fail in human trials, largely due to insufficient efficacy. We hypothesized that adequately powered trials of patient-derived xenografts (PDX) in mice could efficiently define therapeutic activity across heterogeneous tumors. To address this hypothesis, we established a large, publicly available repository of well-characterized leukemia and lymphoma PDXs that undergo orthotopic engraftment, called the Public Repository of Xenografts (PRoXe). PRoXe includes all de-identified information relevant to the primary specimens and the PDXs derived from them. Using this repository, we demonstrate that large studies of acute leukemia PDXs that mimic human randomized clinical trials can characterize drug efficacy and generate transcriptional, functional, and proteomic biomarkers in both treatment-naive and relapsed/refractory disease.

Mutant Calreticulin Requires Both Its Mutant C-terminus and the Thrombopoietin Receptor for Oncogenic Transformation

Somatic mutations in calreticulin (CALR) are present in approximately 40% of patients with myeloproliferative neoplasms (MPN), but the mechanism by which mutant CALR is oncogenic remains unclear. Here, we demonstrate that expression of mutant CALR alone is sufficient to engender MPN in mice and recapitulates the disease phenotype of patients with CALR-mutant MPN. We further show that the thrombopoietin receptor MPL is required for mutant CALR-driven transformation through JAK-STAT pathway activation, thus rendering mutant CALR-transformed hematopoietic cells sensitive to JAK2 inhibition. Finally, we demonstrate that the oncogenicity of mutant CALR is dependent on the positive electrostatic charge of the C-terminus of the mutant protein, which is necessary for physical interaction between mutant CALR and MPL. Together, our findings elucidate a novel paradigm of cancer pathogenesis and reveal how CALR mutations induce MPN.

SIGNIFICANCE

The mechanism by which CALR mutations induce MPN remains unknown. In this report, we show that the positive charge of the CALR mutant C-terminus is necessary to transform hematopoietic cells by enabling binding between mutant CALR and the thrombopoietin receptor MPL.

Complete Surgical Excision Is Essential for the Management of Patients With Breast Implant-Associated Anaplastic Large-Cell Lymphoma

PURPOSE

Breast implant-associated anaplastic large-cell lymphoma (BI-ALCL) is a rare type of T-cell lymphoma that arises around breast implants. The optimal management of this disease has not been established. The goal of this study is to evaluate the efficacy of different therapies used in patients with BI-ALCL to determine an optimal treatment approach.

PATIENTS AND METHODS

In this study, we applied strict criteria to pathologic findings, assessed therapies used, and conducted a clinical follow-up of 87 patients with BI-ALCL, including 50 previously reported in the literature and 37 unreported. A Prentice, Williams, and Peterson model was used to assess the rate of events for each therapeutic intervention.

RESULTS

The median and mean follow-up times were 45 and 30 months, respectively (range, 3 to 217 months). The median overall survival (OS) time after diagnosis of BI-ALCL was 13 years, and the OS rate was 93% and 89% at 3 and 5 years, respectively. Patients with lymphoma confined by the fibrous capsule surrounding the implant had better event-free survival (EFS) and OS than did patients with lymphoma that had spread beyond the capsule (P = .03). Patients who underwent a complete surgical excision that consisted of total capsulectomy with breast implant removal had better OS (P = .022) and EFS (P = .014) than did patients who received partial capsulectomy, systemic chemotherapy, or radiation therapy.

CONCLUSION

Surgical management with complete surgical excision is essential to achieve optimal EFS in patients with BI-ALCL.

Incidence and clinical features of extramedullary multiple myeloma in patients who underwent stem cell transplantation

Extramedullary disease (EMD), defined as an infiltrate of clonal plasma cells at an anatomic site distant from the bone marrow, is an uncommon manifestation of multiple myeloma. Six hundred and sixty-three consecutive patients with multiple myeloma who underwent stem cell transplantation between January 2005 and December 2011 were assessed for the presence of EMD. A cohort of 55 patients with biopsy-proven EMD was identified, comprising 8·3% of the total study population. EMD was present at the time of diagnosis in 14·5% of cases and at the time of relapse in 76% of patients. The most common EMD presentations at relapse were liver involvement and pleural effusions. EMD specimens had high expression of CD44 (92%) and moderate expression of CXCR4. The median overall survival from time of myeloma diagnosis was 4·1 years (95% CI: 3·1, 5·1) and the median overall survival from time of EMD diagnosis was 1·3 years (95% CI: 0·8, 2·3). This report demonstrates that the incidence of EMD has not increased with the introduction of novel agents and stem cell transplantation. The most common EMD presentations in the relapsed setting were liver and pleural fluid. The presence of CD44 and CXCR4 expression may represent new markers of EMD that warrant further investigation.