The highly selective and oral phosphoinositide 3-kinase delta (PI3K-δ) inhibitor roginolisib induces apoptosis in mesothelioma cells and increases immune effector cell composition.

Targeting aberrantly expressed kinases in malignant pleural mesothelioma (MPM) is a promising therapeutic strategy. We here investigated the effect of the novel and highly selective Phosphoinositide 3-kinase delta (PI3K-δ) inhibitor roginolisib (IOA-244) on MPM cells and on the immune cells in MPM microenvironment. To this aim, we analyzed the expression of PI3K-δ by immunohistochemistry in specimens from primary MPM, cell viability and death in three different MPM cell lines treated with roginolisib alone and in combination with ipatasertib (AKT inhibitor) and sapanisertib (mTOR inhibitor). In a co-culture model of patient-derived MPM cells, autologous peripheral blood mononuclear cells and fibroblasts, the tumor cell viability and changes in immune cell composition were investigated after treatment of roginolisib with nivolumab and cisplatin. PI3K-δ was detected in 66/89 (74%) MPM tumors and was associated with reduced overall survival (12 vs. 25 months, P=0.0452). Roginolisib induced apoptosis in MPM cells and enhanced the anti-tumor efficacy of AKT and mTOR kinase inhibitors by suppressing PI3K-δ/AKT/mTOR and ERK1/2 signaling. Furthermore, the combination of roginolisib with chemotherapy and immunotherapy re-balanced the immune cell composition, increasing effector T-cells and reducing immune suppressive cells. Overall, roginolisib induces apoptosis in MPM cells and increases the antitumor immune cell effector function when combined with nivolumab and cisplatin. These results provide first insights on the potential of roginolisib as a therapeutic agent in patients with MPM and its potential in combination with established immunotherapy regimen.

The fifth edition of the WHO classification of mature B-cell neoplasms: open questions for research.

The fifth edition of the World Health Organization Classification of Haematolymphoid Tumours (WHO-HAEM5) is the product of an evidence-based evolution of the revised fourth edition with wide multidisciplinary consultation. Nonetheless, while every classification incorporates scientific advances and aims to improve upon the prior version, medical knowledge remains incomplete and individual neoplasms may not be easily subclassified in a given scheme. Thus, optimal classification requires ongoing study, and there are certain aspects of some entities and subtypes that require further refinements. In this review, we highlight a selection of these challenging areas to prompt more research investigations. These include (1) a 'placeholder term' of splenic B-cell lymphoma/leukaemia with prominent nucleoli (SBLPN) to accommodate many of the splenic lymphomas previously classified as hairy cell leukaemia variant and B-prolymphocytic leukaemia, a clear new start to define their pathobiology; (2) how best to classify BCL2 rearrangement negative follicular lymphoma including those with BCL6 rearrangement, integrating the emerging new knowledge on various germinal centre B-cell subsets; (3) what is the spectrum of non-IG gene partners of MYC translocation in diffuse large B-cell lymphoma/high-grade B-cell lymphoma and how they impact MYC expression and clinical outcome; how best to investigate this in a routine clinical setting; and (4) how best to define high-grade B-cell lymphoma not otherwise specified and high-grade B-cell lymphoma with 11q aberrations to distinguish them from their mimics and characterise their molecular pathogenetic mechanism. Addressing these questions would provide more robust evidence to better define these entities/subtypes, improve their diagnosis and/or prognostic stratification, leading to better patient care. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

The 5th edition of the World Health Organization Classification of mature lymphoid and stromal tumors - an overview and update.

The purpose of this review is to give an overview on the conceptual framework and major developments of the upcoming 5th edition of the World Health Organization (WHO) Classification of Haematolymphoid tumours (WHO-HAEM5) and to highlight the most significant changes made in WHO-HAEM5 compared with the revised 4th edition (WHO-HAEM4R) of lymphoid and stromal neoplasms. The changes from the revised 4th edition include the reorganization of entities by means of a hierarchical system that is realized throughout the 5th edition of the WHO classification of tumors of all organ systems, a modification of nomenclature for some entities, the refinement of diagnostic criteria or subtypes, deletion of certain entities, and introduction of new entities. For the first time, tumor-like lesions, mesenchymal lesions specific to lymph node and spleen, and germline predisposition syndromes associated with the lymphoid neoplasms are included in the classification.

Genetic Characterization of Primary Mediastinal B-Cell Lymphoma: Pathogenesis and Patient Outcomes.

PURPOSE: Primary mediastinal large B-cell lymphoma (PMBCL) is a rare aggressive lymphoma predominantly affecting young female patients. Large-scale genomic investigations and genetic markers for risk stratification are lacking. PATIENTS AND METHODS: To elucidate the full spectrum of genomic alterations, samples from 340 patients with previously untreated PMBCL were investigated by whole-genome (n = 20), whole-exome (n = 78), and targeted (n = 308) sequencing. Statistically significant prognostic variables were identified using a multivariable Cox regression model and confirmed by L1/L2 regularized regressions. RESULTS: Whole-genome sequencing revealed a commonly disrupted p53 pathway with nonredundant somatic structural variations (SVs) in TP53-related genes (TP63, TP73, and WWOX) and identified novel SVs facilitating immune evasion (DOCK8 and CD83). Integration of mutation and copy-number data expanded the repertoire of known PMBCL alterations (eg, ARID1A, P2RY8, and PLXNC1) with a previously unrecognized role for epigenetic/chromatin modifiers. Multivariable analysis identified six genetic lesions with significant prognostic impact. CD58 mutations (31%) showed the strongest association with worse PFS (hazard ratio [HR], 2.52 [95% CI, 1.50 to 4.21]; P < .001) and overall survival (HR, 2.33 [95% CI, 1.14 to 4.76]; P = .02). IPI high-risk patients with mutated CD58 demonstrated a particularly poor prognosis, with 5-year PFS and OS rates of 41% and 58%, respectively. The adverse prognostic significance of the CD58 mutation status was predominantly observed in patients treated with nonintensified regimens, indicating that dose intensification may, to some extent, mitigate the impact of this high-risk marker. By contrast, DUSP2-mutated patients (24%) displayed durable responses (PFS: HR, 0.2 [95% CI, 0.07 to 0.55]; P = .002) and prolonged OS (HR, 0.11 [95% CI, 0.01 to 0.78]; P = .028). Upon CHOP-like treatment, these patients had very favorable outcome, with 5-year PFS and OS rates of 93% and 98%, respectively. CONCLUSION: This large-scale genomic characterization of PMBCL identified novel treatment targets and genetic lesions for refined risk stratification. DUSP2 and CD58 mutation analyses may guide treatment decisions between rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone and dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab.

Inhibition of glutaminase-1 in DLBCL potentiates venetoclax-induced antitumor activity by promoting oxidative stress.

Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma in adults, but first-line immunochemotherapy fails to produce a durable response in about one-third of the patients. Because tumor cells often reprogram their metabolism, we investigated the importance of glutaminolysis, a pathway converting glutamine to generate energy and various metabolites, for the growth of DLBCL cells. Glutaminase-1 (GLS1) expression was robustly detected in DLBCL biopsy samples and cell lines. Both pharmacological inhibition and genetic knockdown of GLS1 induced cell death in DLBCL cells regardless of their subtype classification, whereas primary B cells remained unaffected. Interestingly, GLS1 inhibition resulted not only in reduced levels of intermediates of the tricarboxylic acid cycle but also in a strong mitochondrial accumulation of reactive oxygen species. Supplementation of DLBCL cells with α-ketoglutarate or with the antioxidant α-tocopherol mitigated oxidative stress and abrogated cell death upon GLS1 inhibition, indicating an essential role of glutaminolysis in the protection from oxidative stress. Furthermore, the combination of the GLS1 inhibitor CB-839 with the therapeutic BCL2 inhibitor ABT-199 not only induced massive reactive oxygen species (ROS) production but also exhibited highly synergistic cytotoxicity, suggesting that simultaneous targeting of GLS1 and BCL2 could represent a novel therapeutic strategy for patients with DLBCL.

Targeted panel sequencing in the routine diagnosis of mature T- and NK-cell lymphomas: report of 128 cases from two German reference centers.

Diagnosing any of the more than 30 types of T-cell lymphomas is considered a challenging task for many pathologists and currently requires morphological expertise as well as the integration of clinical data, immunophenotype, flow cytometry and clonality analyses. Even considering all available information, some margin of doubt might remain using the current diagnostic procedures. In recent times, the genetic landscape of most T-cell lymphomas has been elucidated, showing a number of diagnostically relevant mutations. In addition, recent data indicate that some of these genetic alterations might bear prognostic and predictive value. Extensive genetic analyses, such as whole exome or large panel sequencing are still expensive and time consuming, therefore limiting their application in routine diagnostic. We therefore devoted our effort to develop a lean approach for genetic analysis of T-cell lymphomas, focusing on maximum efficiency rather than exhaustively covering all possible targets. Here we report the results generated with our small amplicon-based panel that could be used routinely on paraffin-embedded and even decalcified samples, on a single sample basis in parallel with other NGS-panels used in our routine diagnostic lab, in a relatively short time and with limited costs. We tested 128 available samples from two German reference centers as part of our routine work up (among which 116 T-cell lymphomas), which is the largest routine diagnostic series reported to date. Our results showed that this assay had a very high rate of technical success (97%) and could detect mutations in the majority (79%) of tested T-cell lymphoma samples.

Activity of tafasitamab in combination with rituximab in subtypes of aggressive lymphoma.

Background: Despite recent advances in the treatment of aggressive lymphomas, a significant fraction of patients still succumbs to their disease. Thus, novel therapies are urgently needed. As the anti-CD20 antibody rituximab and the CD19-targeting antibody tafasitamab share distinct modes of actions, we investigated if dual-targeting of aggressive lymphoma B-cells by combining rituximab and tafasitamab might increase cytotoxic effects. Methods: Antibody single and combination efficacy was determined investigating different modes of action including direct cytotoxicity, antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) in in vitro and in vivo models of aggressive B-cell lymphoma comprising diffuse large B-cell lymphoma (DLBCL) and Burkitt lymphoma (BL). Results: Three different sensitivity profiles to antibody monotherapy or combination treatment were observed in in vitro models: while 1/11 cell lines was primarily sensitive to tafasitamab and 2/11 to rituximab, the combination resulted in enhanced cell death in 8/11 cell lines in at least one mode of action. Treatment with either antibody or the combination resulted in decreased expression of the oncogenic transcription factor MYC and inhibition of AKT signaling, which mirrored the cell line-specific sensitivities to direct cytotoxicity. At last, the combination resulted in a synergistic survival benefit in a PBMC-humanized Ramos NOD/SCID mouse model. Conclusion: This study demonstrates that the combination of tafasitamab and rituximab improves efficacy compared to single-agent treatments in models of aggressive B-cell lymphoma in vitro and in vivo.

Frequent ZNF217 mutations lead to transcriptional deregulation of interferon signal transduction via altered chromatin accessibility in B cell lymphoma.

Recent exome-wide studies discovered frequent somatic mutations in the epigenetic modifier ZNF217 in primary mediastinal B cell lymphoma (PMBCL) and related disorders. As functional consequences of ZNF217 alterations remain unknown, we comprehensively evaluated their impact in PMBCL. Targeted sequencing identified genetic lesions affecting ZNF217 in 33% of 157 PMBCL patients. Subsequent gene expression profiling (n = 120) revealed changes in cytokine and interferon signal transduction in ZNF217-aberrant PMBCL cases. In vitro, knockout of ZNF217 led to changes in chromatin accessibility interfering with binding motifs for crucial lymphoma-associated transcription factors. This led to disturbed expression of interferon-responsive and inflammation-associated genes, altered cell behavior, and aberrant differentiation. Mass spectrometry demonstrates that ZNF217 acts within a histone modifier complex containing LSD1, CoREST and HDAC and interferes with H3K4 methylation and H3K27 acetylation. Concluding, our data suggest non-catalytic activity of ZNF217, which directs histone modifier complex function and controls B cell differentiation-associated patterns of chromatin structure.

Novel insights into the pathogenesis of follicular lymphoma by molecular profiling of localized and systemic disease forms.

Knowledge on the pathogenesis of FL is mainly based on data derived from advanced/systemic stages of FL (sFL) and only small cohorts of localized FL (lFL) have been characterized intensively so far. Comprehensive analysis with profiling of somatic copy number alterations (SCNA) and whole exome sequencing (WES) was performed in 147 lFL and 122 sFL. Putative targets were analyzed for gene and protein expression. Overall, lFL and sFL, as well as BCL2 translocation-positive (BCL2+) and -negative (BCL2-) FL showed overlapping features in SCNA and mutational profiles. Significant differences between lFL and sFL, however, were detected for SCNA frequencies, e.g., in 18q-gains (14% lFL vs. 36% sFL; p = 0.0003). Although rare in lFL, gains in 18q21 were associated with inferior progression-free survival (PFS). The mutational landscape of lFL and sFL included typical genetic lesions. However, ARID1A mutations were significantly more often detected in sFL (29%) compared to lFL (6%, p = 0.0001). In BCL2 + FL mutations in KMT2D, BCL2, ABL2, IGLL5 and ARID1A were enriched, while STAT6 mutations more frequently occurred in BCL2- FL. Although the landscape of lFL and sFL showed overlapping features, molecular profiling revealed novel insights and identified gains in 18q21 as prognostic marker in lFL.

Radiation and Dose-densification of R-CHOP in Primary Mediastinal B-cell Lymphoma: Subgroup Analysis of the UNFOLDER Trial.

UNFOLDER (NCT00278408, EUDRACT 2005-005218-19) is a phase-3 trial in patients with aggressive B-cell lymphoma and intermediate prognosis, including primary mediastinal B-cell lymphoma (PMBCL). In a 2 × 2 factorial design, patients were randomized to 6× R-CHOP-14 or R-CHOP-21 (rituximab, cyclophosphamide, doxorubicin, vincristine, and prediso(lo)ne) and to consolidation radiotherapy to extralymphatic/bulky disease or observation. Response was assessed according to the standardized criteria from 1999, which did not include F-18 fluordesoxyglucose positron emission tomography/computed tomography (FDG-PET) scans. Primary end point was event-free survival (EFS). A subgroup of 131 patients with PMBCLs was included (median age, 34 y; 54% female, 79% elevated lactate dehydrogenase (LDH), 20% LDH >2× upper limit of normal [ULN], and 24% extralymphatic involvement). Eighty-two (R-CHOP-21: 43 and R-CHOP-14: 39) patients were assigned to radiotherapy and 49 (R-CHOP-21: 27, R-CHOP-14: 22) to observation. The 3-year EFS was superior in radiotherapy arm (94% [95% confidence interval (CI), 89-99] versus 78% [95% CI, 66-89]; P = 0.0069), due to a lower rate of partial responses (PRs) (2% versus 10%). PR triggered additional treatment, mostly radiotherapy (n = 5; PR: 4; complete response/unconfirmed complete response: 1). No significant differences were observed in progression-free survival (PFS) (95% [95% CI, 90-100] versus 90% [95% CI, 81-98]; P = 0.25) nor in overall survival (OS) (98% [95% CI, 94-100] versus 96% [95% CI, 90-100]; P = 0.64). Comparing R-CHOP-14 and R-CHOP-21, EFS, PFS, and OS were not different. A prognostic marker for adverse outcome was elevated LDH >2× ULN (EFS: P = 0.016; PFS: P = 0.0049; OS: P = 0.0014). With the limitation of a pre-PET-era trial, the results suggest a benefit of radiotherapy only for patients responding to R-CHOP with PR. PMBCL treated with R-CHOP have a favorable prognosis with a 3-year OS of 97%.

Indolyl-chalcone derivatives trigger apoptosis in cisplatin-resistant mesothelioma cells through aberrant tubulin polymerization and deregulation of microtubule-associated proteins.

Introduction: Malignant pleural mesothelioma (MPM) is a neoplasm with dismal prognosis and notorious resistance to the standard therapeutics cisplatin and pemetrexed. Chalcone derivatives are efficacious anti-cancer agents with minimal toxicity and have, therefore, gained pharmaceutical interest. Here, we investigated the efficacy of CIT-026 and CIT-223, two indolyl-chalcones (CITs), to inhibit growth and viability of MPM cells and defined the mechanism by which the compounds induce cell death. Methods: The effects of CIT-026 and CIT-223 were analyzed in five MPM cell lines, using viability, immunofluorescence, real-time cell death monitoring, and tubulin polymerization assays, along with siRNA knockdown. Phospho-kinase arrays and immunoblotting were used to identify signaling molecules that contribute to cell death. Results: CIT-026 and CIT-223 were toxic in all cell lines at sub-micromolar concentrations, in particular in MPM cells resistant to cisplatin and pemetrexed, while normal fibroblasts were only modestly affected. Both CITs targeted tubulin polymerization via (1) direct interaction with tubulin and (2) phosphorylation of microtubule regulators STMN1, CRMP2 and WNK1. Formation of aberrant tubulin fibers caused abnormal spindle morphology, mitotic arrest and apoptosis. CIT activity was not reduced in CRMP2-negative and STMN1-silenced MPM cells, indicating that direct tubulin targeting is sufficient for toxic effects of CITs. Discussion: CIT-026 and CIT-223 are highly effective inducers of tumor cell apoptosis by disrupting microtubule assembly, with only modest effects on non-malignant cells. CITs are potent anti-tumor agents against MPM cells, in particular cells resistant to standard therapeutics, and thus warrant further evaluation as potential small-molecule therapeutics in MPM.

Transdifferentiation, phenotypic infidelity, progression, and transformation in T/NK-cell neoplasms: Report from the 2021 SH/EAHP Workshop.

OBJECTIVES: Sessions 8 and 9 of the 2021 Society for Hematopathology and the European Association for Haematopathology Workshop aimed to collect examples of transdifferentiation, lineage infidelity, progression, and transformation in precursor and mature T/natural killer (NK)-cell neoplasms. METHODS: Twenty-eight cases were submitted and analyzed, with whole-exome sequencing and genome-wide RNA expression analysis performed in a subset of the cases. RESULTS: In session 8, 7 T-lymphoblastic lymphoma/leukemia cases were received that showed transdifferentiation to clonally related mature myeloid hematopoietic neoplasms, including 6 histiocytic/dendritic cell lineage neoplasms and a mast cell sarcoma. Session 9 included 21 mature T-cell neoplasms that were grouped into 3 themes. The first one addressed phenotypic infidelity in mature T-cell lymphomas (TCLs) and included 8 TCLs expressing aberrant antigens, mimicking classic Hodgkin and non-Hodgkin B-cell lymphomas. The second theme addressed disease progression in TCL and included 5 cutaneous T-cell lymphoproliferative disorders and 2 T-cell large granular lymphocyte proliferations with subsequent progression to systemic TCL. The third theme included 6 patients with TCL with T-follicular helper phenotype, mainly angioimmunoblastic T-cell lymphoma, with concurrent/subsequent clonal hematopoiesis or myeloid neoplasms and/or subsequent/concomitant diffuse large B-cell lymphoma. CONCLUSIONS: This cohort of cases allowed us to illustrate, discuss, and review current concepts of transdifferentiation, aberrant antigen expression, and progression in various T/NK-cell neoplasms.

Progression of follicular lymphoma and related entities: Report from the 2021 SH/EAHP Workshop.

OBJECTIVES: The 2021 Society for Hematopathology and European Association for Haematopathology Workshop addressed the molecular and cytogenetic underpinnings of transformation and transdifferentiation in lymphoid neoplasms. METHODS: Session 4, "Transformations of Follicular Lymphoma," and session 5, "Transformations of Other B-Cell Lymphomas," included 45 cases. Gene alteration analysis and expression profiling were performed on cases with submitted formalin-fixed, paraffin embedded tissue. RESULTS: The findings from session 4 suggest that "diffuse large B-cell lymphoma/high-grade B-cell lymphoma with rearrangements of MYC and BCL2" is a distinct category arising from the constraints of a preexisting BCL2 translocation. TdT expression in aggressive B-cell lymphomas is associated with MYC rearrangements, immunophenotypic immaturity, and a dismal prognosis but must be differentiated from lymphoblastic -lymphoma. Cases in session 5 illustrated unusual morphologic and immunophenotypic patterns of transformation. Additionally, the findings support the role of cytogenetic abnormalities-specifically, MYC and NOTCH1 rearrangements-as well as single gene alterations, including TP53, in transformation. CONCLUSIONS: Together, these unique cases and their accompanying molecular and cytogenetic data suggest potential mechanisms for and unusual patterns of transformation in B-cell lymphomas and indicate numerous opportunities for further study.

Large B-Cell Lymphomas in the 5th Edition of the WHO-Classification of Haematolymphoid Neoplasms-Updated Classification and New Concepts.

The family/class of the large B-cell lymphomas (LBCL) in the 5th edition of the World Health Organization (WHO) classification of haematolymphoid tumors (WHO-HAEM5) features only a few major changes as compared to the 4th edition. In most entities, there are only subtle changes, many of them only representing some minor modifications in diagnostic terms. Major changes have been made in the diffuse large B-cell lymphomas (DLBCL)/high-grade B-cell lymphomas (HGBL) associated with MYC and BCL2 and/or BCL6 rearrangements. This category now consists of MYC and BCL2 rearranged cases exclusively, while the MYC/BCL6 double hit lymphomas now constitute genetic subtypes of DLBCL, not otherwise specified (NOS) or of HGBL, NOS. Other major changes are the conceptual merger of lymphomas arising in immune-privileged sites and the description of LBCL arising in the setting of immune dysregulation/deficiency. In addition, novel findings concerning underlying biological mechanisms in the pathogenesis of the different entities are provided.

Transformations of marginal zone lymphomas and lymphoplasmacytic lymphomas: Report from the 2021 SH/EAHP Workshop.

OBJECTIVES: To summarize the conclusions of the 2021 Society for Hematopathology/European Association for Haematopathology workshop regarding transformations of marginal zone lymphoma (MZL) and lymphoplasmacytic lymphoma (LPL). METHODS: Nineteen cases were submitted to this portion of the workshop. Additional studies were performed in cases with sufficient material. RESULTS: Cases included splenic MZL (n = 4), splenic diffuse red pulp small B-cell lymphoma (n = 2), nodal MZL (n = 4), extranodal MZL (n = 1), and LPL (n = 8). The most common transformation was to diffuse large B-cell lymphoma (DLBCL), but others included classic Hodgkin lymphoma, high-grade B-cell lymphomas with MYC and BCL6 rearrangements, plasmablastic lymphoma, and plasma cell leukemia. Two splenic MZLs with transformation to DLBCL contained t(14;19)(q32;q13.3) IGH::BCL3 rearrangements in both samples. Paired sequencing studies in 5 MZLs with transformation to clonally related DLBCL identified a variety of mutations and gene fusions at the time of transformation, including CARD11, IGH::MYC, NOTCH2, P2RY8, TBLX1X1, and IGH::CD274. CONCLUSIONS: Marginal zone lymphoma and LPL may undergo a variety of transformation events, most commonly to DLBCL, which is usually, although not always, directly clonally related to the underlying low-grade lymphoma. Multiparameter analysis including broad-based sequencing studies can assist in the diagnosis and classification of these uncommon cases.

B-cell lineage neoplasms transdifferentiating into histiocytic/dendritic cell neoplasms: diversity, differentiation lineage, genomic alterations, and therapy: Report from the 2021 SH/EAHP Workshop.

OBJECTIVES: To report findings from the 2021 Society for Hematopathology/European Association for Haematopathology Workshop within the category of B-cell lineage neoplasms' transdifferentiation into histiocytic/dendritic cell neoplasms (HDCNs). METHODS: The workshop panel reviewed 29 cases, assigned consensus diagnoses, and summarized findings. RESULTS: The specific diagnoses of transdifferentiated HDCN tumors were histiocytic sarcoma (16); Langerhans cell histiocytosis/sarcoma (5); indeterminate DC tumor (1); and HDCN, unclassifiable (1). Approximately one-third of the patients reviewed had follicular lymphoma; lymphoblastic leukemia/lymphoma; or another B-cell lymphoma, most commonly chronic lymphocytic leukemia/small lymphocytic lymphoma. There was a 3:1 preponderance toward women, median patient age was 60 years, and the median interval between the initial diagnosis of B-cell lineage neoplasm and HDCN was 4 to 5 years. The submitted cases have demonstrated substantial heterogeneity as well as overlapping immunophenotypic and other features. Comprehensive genomic DNA sequencing revealed alterations enriched in the MAPK pathway. Based on shared and distinct alterations seen in HDCNs and the preceding lymphomas, both linear and divergent clonal evolutionary pathways were inferred. Furthermore, RNA sequencing performed in a subset of cases yielded new insights into markers that could be useful for more precise cell lineage identification. The panel has thus proposed an updated algorithm for HDCN lineage assignment. The outcome of transdifferentiated HDCNs was poor, but the MAPK signaling pathway emerges as a potentially attractive therapeutic target. CONCLUSIONS: Transdifferentiated HDCNs demonstrate heterogeneity and pose diagnostic challenges with regard to exact classification, but the in-depth characterization of the submitted cases have added to our understanding of the secondary HDCNs transdifferentiated from B-cell lymphoma/leukemia. Continuous efforts focusing on deciphering the specific cell lineage and differentiation state of these tumors will be critical for their accurate classification. Comprehensive molecular characterization of HDCNs may be informative in this regard. With the list of novel pharmacologic inhibitors of the MAPK pathway continuing to expand, improved outcomes for HDCN can be expected.

Bile duct tissue acquisition by cholangioscopy-guided cryobiopsy technique: first-in-human application.

Video 1Case description and video in cholangioscopic view demonstrating bile duct tissue acquisition by cholangioscopy-guided cryobiopsy technique.

Phenotypic and genotypic infidelity in B-lineage neoplasms, including transdifferentiation following targeted therapy: Report from the 2021 SH/EAHP Workshop.

OBJECTIVES: Session 2 of the 2021 Society for Hematopathology and European Association for Haematopathology Workshop collected examples of lineage infidelity and transdifferentiation in B-lineage neoplasms, including after targeted therapy. METHODS: Twenty cases were submitted. Whole-exome sequencing and genome-wide RNA expression analysis were available on a limited subsample. RESULTS: A diagnosis of B-cell acute lymphoblastic leukemia (B-ALL) was rendered on at least 1 biopsy from 13 patients. There was 1 case of acute myeloid leukemia (AML); the remaining 6 cases were mature B-cell neoplasms. Targeted therapy was administered in 7 cases of B-ALL and 4 cases of mature B-cell neoplasms. Six cases of B-ALL underwent lineage switch to AML or mixed-phenotype acute leukemia at relapse, 5 of which had rearranged KMT2A. Changes in maturational state without lineage switch were observed in 2 cases. Examples of de novo aberrant T-cell antigen expression (n = 2) were seen among the mature B-cell lymphoma cohort, and their presence correlated with alterations in tumor cell gene expression patterns. CONCLUSIONS: This cohort of cases enabled us to illustrate, discuss, and review current concepts of lineage switch and aberrant antigen expression in a variety of B-cell neoplasms and draw attention to the role targeted therapies may have in predisposing neoplasms to transdifferentiation as well as other, less expected changes in maturational status.