ALBERT

Description: Chronic lymphocytic leukemia (CLL) is characterized by the existence of subsets of patients with (quasi)identical, stereotyped B cell receptor immunoglobulins (BcR IG). Patients in certain major stereotyped subsets often display remarkably consistent clinicobiological profiles, suggesting that the study of BcR IG stereotypy in CLL has important implications for understanding disease pathophysiology and refining clinical decision-making. Nevertheless, several issues remain open, especially pertaining to the actual frequency of BcR IG stereotypy and major subsets, as well as the existence of higher-order connections between individual subsets. In order to address these issues, we investigated clonotypic IGHV-IGHD-IGHJ gene rearrangements in a series of 29,856 patients with CLL, by far the largest series worldwide. We report that the stereotyped fraction of CLL peaks at 41% of the entire cohort and that all 19 previously identified major subsets retained their relative size and ranking, while 10 new ones emerged; overall, major stereotyped subsets had a cumulative frequency of 13.5%. Higher-level relationships were evident between subsets, particularly for major stereotyped subsets with unmutated IGHV genes (U-CLL), for which close relations with other subsets, termed 'satellites', were identified. Satellite subsets accounted for 3% of the entire cohort. These results confirm our previous notion that major subsets can be robustly identified and are consistent in relative size, hence representing distinct disease variants amenable to compartmentalized research with the potential of overcoming the pronounced heterogeneity of CLL. Furthermore, the existence of satellite subsets reveals a novel aspect of repertoire restriction with implications for refined molecular classification of CLL.

Description: INTRODUCTION: Chronic lymphocytic leukemia (CLL)-like monoclonal B cell lymphocytosis (MBL) is considered a precursor of CLL. It is found in 5-10% of elderly healthy individuals and shows a progression rate to CLL requiring therapy of 1.1% per year. A balance between microenvironmental factors and intrinsic properties of the emerging B cell clone may be decisive for the transition from MBL to CLL, although biomarkers of progression remain unknown. The objective is to describe biological markers (B cell gene expression profiles and serum cytokine levels) that predict progression from MBL to CLL. METHODS: Gene expression profiles of clonal B cells from 14 MBL subjects (median age: 76 years, clonal B cells: 0.5-4.3 x109/L) were evaluated. With a median follow-up from analysis of 59 months (range: 10-77), 3 cases (21.4%) had progressed to CLL Binet stage A at last follow-up (clonal lymphocytosis 〉5x109/L, range: 6.2-7.9). Clonal B cells (CD19+CD5+) were isolated from peripheral blood by immunomagnetic methods (Miltenyi Biotec). Extracted RNA (RIN〉7) was hybridized to GeneChip Human Gene 2.0 ST arrays (Affymetrix). Gene expression profiles were compared between MBL cases that progressed to CLL (P-MBL, n=3) and non-progressive MBL cases (NP-MBL, n=11). Differential gene expression was evaluated employing linear models for microarrays in R, and genes with P1.5 or 5x109/L, range: 6.4-17.3). Clonal B cells and cytokine levels were compared between P-MBL (n=5) and NP-MBL (N=36). For cytokine levels, the optimal cut-off values to stratify MBL cases according to their progression risk were assessed using the maxstat R package, whereas for clonal B cells a cut-off value of 3.9 x109/L was considered according to the results obtained by Kostopoulos et al (Blood Cancer J, 2017). The effect of different covariates on progression-free survival was evaluated using log-rank test. Cox proportional hazards regression models were performed to assess their independent prognostic value. P

Description: Abstract 4631 BACKGROUND The precursor of nucleotide biosynthesis acadesine or 5-aminoimidazole-4-carboxamide (AICA) riboside induces apoptosis in CLL cells, and other lymphoproliferative diseases such as splenic marginal zone lymphoma and mantle cell lymphoma. This effect is selective for B-cells, at least ex vivo, however there is no evidence of whether this cytotoxic effect depends on well known prognostic variables such as ZAP-70 expression or IgVH mutational status. AIM To analyse ex vivo the cytotoxic effect of acadesine on peripheral CLL cells and correlate it with prognostic variables. METHODS Cryopreserved cells from 62 CLL patients were incubated ex vivo with acadesine at 0.2, 0.5, and 1 mM for 24 hours. Viability was determined by flow cytometry using Annexin V-FITC and DAPI staining combined with CD19-PE and CD3-PerCP to differentiate cell viability of B- and T-cells. Cells were considered sensitive to the drug when the percentage of acadesine-induced apoptosis was equal to or higher than 15% with respect to the viability of control cells. The mutational status of IgVH genes was determined by RT-PCR amplification using a set of six VH family-specific primers (VH1 through VH6) along with primers complementary to the constant region (IgM and IgG). Products were directly sequenced from both strands using the Big Dye Terminator Cycle Sequencing Ready Reaction (version 3.1, Applied Biosystems). Sequencing analysis and alignments were performed with use of V-QUEST software and the online international immunogenetics information (IMGT) data library. Samples in which fewer than 2 percent of base pairs differed from those of the consensus sequence have been considered unmutated. ZAP-70 expression was quantified by flow cytometry (cut-off:20%) and cytogenetic alterations associated with CLL (trisomy 12, del13q, del 17p and del11q) were determined by FISH. RESULTS After 24h of ex vivo incubation, 0.2 mM acadesine induced a significant cytotoxic effect (〉 15%) in 31 out of 62 patients (50%). Higher concentrations, 0.5 mM and 1 mM, induced a significant effect in 91.4% (57 of 62 patients) and 98% (61 of 62 patients), respectively. The viabilities (mean ±SD) of the different culture conditions are shown in the table. The cytotoxic effect induced by acadesine was analyzed with respect to the IgVH mutational status and ZAP-70 expression. No significant differences were observed between cases with unmutated IgVH (n=20) and mutated IgVH(n=37), or between ZAP-70 positive (n=24) and ZAP-70 negative cases (n=34). Interestingly, 5 cases showing deletion of 17p were sensitive to treatment with acadesine, in agreement with previously published studies showing that acadesine-induced apoptosis is independent of p53. Only one case showing deletion 17p and VH3-21 usage was not sensitive to acadesine. CONCLUSIONS Acadesine induces apoptosis in B-cells from CLL regardless of ZAP-70 expression, IgVH mutational status and 17p status. Disclosures: Campàs: Advancell: Employment. de Frías:Advancell: Employment.

Description: Basis. Abnormalities in chromosome 8 (8p-/8q+) are observed in 2-5% of CLL patients. Microarray studies have revealed up to 30-40% of 8 alterations in del(17p) patients and an independent association with poor outcome. Large series assessing CLL patients with 8p-/8q+ are scarce. Aims. 1. To describe the frequency of 8q gains (8q+) and 8p losses (8p-) in CLL patients with del(17p); 2. To compare cytogenetic and clinical characteristics between patients with 8p-/8q+ (Alt-chr8) and those with normal chromosome 8 (N-chr8); 3. To assess their prognostic value. Patients and methods. From 2,249 patients included in the Spanish CLL database, 75 del(17p) cases were selected. Gains of MYC (8q24) and losses of LPL (8p22) were studied by FISH. Clinical and cytogenetic data of Alt-chr8 and N-chr8 were compared. Results. 8p- and/or 8q+ were found in 21/75 patients (28%). In the Alt-chr8 group, 8q+ was more frequent than 8p- (71% vs. 52%) and 29% showed concomitance of both abnormalities, suggesting the presence of i(8q). Six different FISH patterns were identified, some of them coexisting in the same patient (Table 1). Conventional cytogenetics data were available in 47 cases (15 Alt-chr8 and 32 N-chr8). Alt-chr8 group showed a higher median number of alterations and frequency of complex karyotypes (P=0.048 and P=0.013). In the Alt-chr8 group, the karyotype revealed 8p-/8q+ in 3 patients and in 9 cases with abnormal karyotype, the presence of marker chromosomes, added material and/or cryptic alterations would explain the FISH results (Table 1). From 66 cases, routine FISH data (13q, 12 and 11q) were available and no significant differences were detected among Alt-chr8 and N-chr8, as with other clinical and analytical parameters at diagnosis. Of note, shorter Overall Survival (OS) was observed for Alt-chr8, although differences were only significant for patients with 8p- (P=0.012, Figure 1). Interestingly, for 3 patients of Alt-chr8 group, previous non-del(17p) samples already presented 8p-/8q+. Conclusions. 1. In CLL patients with del(17p), detection of 8p- and/or 8q+ is associated with an increased karyotypic complexity and a worse outcome; 2. 8p-/8q+ could act as a primary event that trigger del(17p). More cases are required to confirm this hypothesis. Acknowledgments.PI11/01621; RD12/0036/0044, RD12/0036/0069; 2014/SGR585; Fundació La Caixa. Table 1. Karyotypes and FISH results of patients with del(17p) and Alt-chr8. Conventional Cytogenetics FISH ID Karyotype % del(17p) Chromosome 8 alteration % Pattern* 1 46,XX,del(8)(p21),add(10)(q26),add(17)(p13),+2ac[5]/47,XX,+12,add(17)(p13),del(18)(q21),add(22)(q13)[3] 80 20 1O2G 8p- 2 - 95 75 3 46,XX,add(6)(q24),add(14)(q32,3),i(17)(q10)[6]/46,XX[8] 95 75 4 - 76 50 5 45,XY,-5,-9,-15,add(17)(p13),+18,-21,+2mar[13]/46,XY[37] 70 17 6 46,X,der(X),add(8)(p23),del(13)(q12q22),add(17)(p13)[11]/46,XX[13] 10 32 1O3G 8p- and 8q+ 7 - 95 64 8 45,XY,add(3)(q29),del(4)(q26q35),der(7)(1p36-1p32::7p22-7q32::15q22-15q26), -8,der(9),del(13)(q21q34),-15,-17,-18,+19,add(19)(p13),+2mar,+ac[17]/46,XY[3] 78 34/21 1O3G/2O3G 9 44,X,-X,-6,der(13;15)(q10;q10),add(17)(p13),-20,+mar[13]/46,XX[7] 95 10/23 1O3G/1O2G 10 - 95 66/31 11 45,XY,add(6)(q22),del(11)(q11q22),-17[15]/44,XY,add(6)(q22),del(11)(q11q22),-17,-20,-22,+mar[2] 87 40/24 12 46,XX,del(13)(q14q21)[2]/45,X,-X,del(13)(q14q21)[3]/45,XX,add(3)(q27), t(9;10)(q21;q22),+12,der(12)t(12;17)(q11;p11),del(13)(q14q21),-14,-17[7]/46,XX[8] 70 62 2O3G 8q+ 13 46,XY[30] 14 88 14 46,XY[13] 80 82 15 47,XY,+12[8]/46,XY,add(1)(p34),add(2)(q34),t(11;22)(p14;q11),+12,-22[15]/46,XY[11] 75 18 16 43,X,-X,del(2)(p15),+4,-7,add(11)(q21),-12,-13,add(14)(q32),add(17)(p11)[6]/46,XX[9] 19 14 17 45,XY,del(6)(q?),-9,add(14)(q32),-22,+mar[9]/ 46,XY,del(6)(q?),add(17)(p13),add(19)(q13)[21] 55 23 18 45,XY,add(6)(p11),-22[13]/46,XY,i(17)(q10)[5]/46,XY[16] 16 57 19 - 70 66 2O4G 20 - 90 81 2OnG 21 46,XY[11] 43 60 4O4G Tetraploid *O: LPL signal in orange, G: MYC signal in green. Figure 1. Kaplan Meier plots for OS and (A) 8p- and/or 8q+, (B) 8p- or (C) 8q+. Figure 1. Kaplan Meier plots for OS and (A) 8p- and/or 8q+, (B) 8p- or (C) 8q+. Disclosures No relevant conflicts of interest to declare.

Description: INTRODUCTION: CXCL9, CXCL10 and CXCL11 (CXCL9-10-11) are closely related cytokines that specifically bind to their receptor CXCR3. They act inducing chemotaxis, proliferation and/or cytotoxicity of CD4+ Th1 and cytotoxic T cells, which express CXCR3. Although the CXCL9-10-11/CXCR3 axis promotes immune activation, their pro- or anti-tumor effects in chronic lymphocytic leukemia (CLL) remain controversial. The aims of this study are: 1. To investigate serum levels of CXCL9-10-11 and the protein expression of their receptor CXCR3, as well as Th1 and cytotoxic gene expression signatures and protein expression of the cytotoxic molecules granzyme B and perforin in peripheral blood (PB) CD4+ T cells of controls, CLL-like monoclonal B-cell lymphocytosis (MBL) and CLL Binet stage A patients. 2. To assess the correlations between all previous parameters. 3. To evaluate Th1, cytotoxic and PD1+ T cell populations during disease progression. METHODS: Samples from 52 MBL subjects, 61 untreated CLL patients (Binet stage A/B [CLL-A/CLL-B]: 53/8) and 31 age-matched controls were employed. Serum levels (pg/mL) of CXCL9-10-11 were measured in 24 controls, 41 MBL and 44 CLL-A patients using Human CXCL9/MIG Quantikine ELISA Kit (R&D Systems) and U-PLEX Platform (Meso Scale Discovery). In addition, cryopreserved PB mononuclear cells from 8 controls, 11 MBL, 10 CLL-A and 8 CLL-B were studied by flow cytometry. Anti-CD3, anti-CD4, anti-granzyme B, anti-perforin, anti-CXCR3 and anti-PD1 antibodies, FVS510 and Fixation/Permeabilization Kit were used for cell staining (BD Biosciences). Protein expression of CXCR3, granzyme B, perforin and PD1 (measured as percentage of positive cells in PB CD4+ T cells) was assessed using FACSCanto II cytometer (BD Biosciences). In addition, purified CD4+ cells from PB (purity≥90%) were isolated by immunomagnetic methods (Miltenyi Biotec) to analyze gene expression in 9 controls, 13 MBL and 14 CLL-A patients. Extracted RNA (RIN〉7) was hybridized to GeneChip Human Gene 2.0 ST arrays (Affymetrix). Differential gene expression was evaluated with linear models in R, and genes with P-value1.5 were considered differentially expressed. Linear regression and Pearson correlations were calculated to evaluate the relationship between the different components of the CXCL9-10-11/CXCR3 axis (Figure 1). P-values0.8 for 6/7 genes). Significant positive correlations were also observed between CXCR3 protein expression and cytotoxic genes as well as granzyme B protein (Table 2). Protein expression of CXCR3 and cytotoxic molecules were similarly increased in the different stages of the disease. However, CLL-B patients displayed an increased percentage of CD4+ T cells expressing PD1 (around 7% in MBL and CLL-A versus 16% in CLL-B), although significance was not achieved (Table 1). CONCLUSIONS: 1. The increased levels of the different components of the CXCL9-10-11/CXCR3 axis in MBL and CLL-A, together with the strong correlations observed, point to an important activation of this molecular pathway in the first stages of the disease. 2. Correlations between CXCR3 and Th1/cytotoxic genes/proteins suggest that the increased Th1/cytotoxic features of CD4+ T cells in MBL and CLL-A are triggered by CXCL9-10-11/CXCR3 stimulation, and might be considered as a potential target for CLL immunotherapy. 3. The lower percentage of PD1+ CD4+ T cells in MBL/CLL-A may allow efficient effector Th1/cytotoxic responses at these stages of the disease. ACKNOWLEDGEMENTS. PI11/01621, PI15/00437, 2017/SGR437, Fundació La Caixa, Fundación Española de Hematología y Hemoterapia (FEHH). Disclosures Gimeno: Abbvie: Speakers Bureau; JANSSEN: Consultancy, Speakers Bureau. Rai:Genentech/Roche: Membership on an entity's Board of Directors or advisory committees; Pharmacyctics: Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees; Cellectis: Membership on an entity's Board of Directors or advisory committees. Abrisqueta:Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Other: Travel, Accommodations, expenses, Speakers Bureau; Abbvie: Consultancy, Honoraria, Other: Travel, Accommodations, expenses, Speakers Bureau; Roche: Consultancy, Honoraria, Other: Travel, Accommodations, expenses, Speakers Bureau. Bosch:Acerta: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Kyte: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; AstraZeneca: Honoraria, Research Funding; F. Hoffmann-La Roche Ltd/Genentech, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.

Description: Introduction: MYC rearrangements (MYCr) occur in 5 to 15% of diffuse large B-cell lymphomas (DLBCL) and 20 to 35% of high-grade B-cell lymphoma, NOS (HGBL-NOS), are a defining criterion of the category HGBL with rearrangements of MYC and/or BCL2/BCL6 (HGBL, with MYCr and BCL2/BCL6), and may be present in 90% of Burkitt lymphoma. The current WHO classification considers cytogenetic techniques as the appropriate tool to detect MYCr but does not define how to approach to the identification of such alteration. As the global incidence of MYCr in large B-cell lymphomas (LBCL) is low, it is necessary to clarity whether FISH or other cytogenetic methods have to be applied to all LBCL or only in selected cases. We previously identified LMO2 as a potential surrogate marker of MYCr in LBCL (Colomo L, Am J Surg Pathol 2017). Our aim with this study is to confirm this observation and evaluate the clinical impact of this marker in the survival of patients with LBCL. Methods: We have prospectively studied between September 2014 and July 2019 a new series of 180 LBCL including patients with DLBCL, HGBL, with HGBL, with MYCr and BCL2/BCL6, HGBL-NOS and transformed low-grade lymphomas into DLBCL (tDLBCL) diagnosed according to WHO criteria. LMO2 (clone 1A9-1), MYC (clone Y69) and a common immunohistochemistry (IHC) panel of B and T-cell markers have been used for the histological categorization of the cases, using whole tissue sections. The cutoff for LMO2 and MYC were 30% and 40%, respectively. MYC and BCL6 genes were studied using break apart probes, and BCL2 gene using dual-color dual-fusion probes (IGH/BCL2), all from Vysis-Abbott. We have statistically correlated the loss of expression of LMO2 and the overexpression of MYC with the presence or absence of MYCr. Moreover, we performed survival analyses assessing the clinical impact of LMO2 in a series of 162 LBCL patients (112 DLBCL, 20 HGBL, with MYCr and BCL2/BCL6, 4 HGBL-NOS and 26 tDLBCL). The survival series included cases diagnosed before 2014 with IHC and FISH data. Results: The prospective series included 132 patients with DLBCL (78M/52F; median age 67 years, range 35-95), 9 HGBL, with MYCr and BCL2/BCL6 (5M/4F; median age 67 years, range 42-85), 4 HGBL-NOS (2M/2F; median age 58 years, range 42-89), and 35 tDLBCL (31 transformed follicular lymphomas, 3 marginal zone lymphoma and 1 lymphoplasmacytic lymphoma; 23M/20F; median age 64 years, range 40-82). LMO2 and MYC were expressed as follows, respectively: 84/130 (65%) and 46/132 (35%) in DLBCL; 1/9 (11%) and 8/9 (89%) in HGBL, with MYCr and BCL2/BCL6; 0/4 and 3/4 (75%) HGBL-NOS; 25/34 (73%) and 7/33 (21%) tDLBCL. MYCr were identified in 9/132 (7%) DLBCL; all HGBL, with MYCr and BCL2/BCL6; 4/4 HGBL-NOS; 7/35 (20%) tDLBCL. The table shows the comparisons between LMO2 and MYC protein expression for the identification of the presence of MYCr in the series of LBCL. Whereas in the whole series LMO2 and MYC had similar results, among CD10-positive cases, LMO2 had better results than MYC and identified better the presence of MYCr than MYC protein expression. The 5-year progression-free survival (PFS) according the diagnostic categories was 59% for DLBCL, 28% for HGBL, with MYCr and BCL2/BCL6, 25% for HGBL-NOS and 22% for tDLBCL (P=0.015). In addition, PFS was significantly lower for the presence of MYCr (26% vs 53%, P=0.02) and MYC IHC expression (35% vs 53%, P=0.005), and showed a positive trend for LMO2 loss of expression (39% vs 52%, P=0.1). The 5-year overall survival (OS) according the diagnostic categories was 67% for DLBCL, 23% for HGBL, with MYCr and BCL2/BCL6, 50% for HGBL-NOS and 77% for tDLBCL (P

Description: Introduction The majority of prognostic indexes in CMML include information extracted from bone marrow (BM) evaluation. The blast count in BM in CMML includes the blast and promonocyte percentage. In the extent of our knowledge there are no data evaluating whether both cells have an equivalent prognostic weight for predicting survival. Recent data indicate that an accurate diagnosis of CMML could be established by assessing the monocyte population distribution by flow cytometry and by evaluating its molecular profile by targeted next-generation sequencing in PB. Our aim was to analyze which variables from our series had an independent prognostic value in order to assess if their addition to the most common prognostic scores for CMML, CPSS and Mayo prognostic model (Mayo), contributed to increase their predictive capacity; or if they allowed us to create a new one. Methods One hundred and fifty patients diagnosed with CMML from 1975 to 2019 from a single institution were evaluated. All patients met 2017 WHO criteria. Complete information was available for the following: BM blast percentage, BM promonocyte percentage, PB blast percentage, circulating immature myeloid cells (IMC), presence of Auer rods and complete blood count. The median overall survival (OS) was 35 months (CI 95%: 30-40). We performed univariate and multivariate survival analyses to establish the prognostic weight of each one. Both C-index and Somers'D (Dxy) were used to compare the prognostic accuracy of the different models. Results Patients characteristics are depicted in Table 1. The prognostic impact of the following items was reviewed: BM blasts; BM promonocytes; the sum of BM blasts and promonocytes; proliferative CMML (CMML-P); monocyte count ≥ 5 x 109/L; transfusional dependency; Hb 〈 100 g/L; platelets 〈 100 x 109/L; IMC; PB blasts; abnormal karyotype; spanish cytogenetic risk classification; sex, and dysmegacaryopoiesis, dysgranylopoiesis and dyserythropoiesis according to WHO criteria. In the univariate analysis for the OS only the following demonstrated an adverse impact: sex (women 50.7m vs men 33.4m, P=0.023), PB blasts (39m vs 11m, P

Description: We conducted a retrospective collaborative study to cytogenetically characterize splenic marginal zone lymphoma (SMZL) and ascertain the prognostic value of chromosomal aberrations. Of 330 cases, 72% displayed an aberrant karyotype, 53% were complex, and 29% had a single aberration. The predominant aberrations were gains of 3/3q and 12q, deletions of 7q and 6q and translocations involving 8q/1q/14q. CD5 expression was detected in 39 of 158 cases (25%). The cytogenetic makeup of the CD5+ group differed significantly from that of the CD5− group. Cases with unmutated IGHV were significantly associated with deletions of 7q and TP53. A strong association was noted between usage of the IGVH1-2 and deletion 7q, 14q alterations, and abnormal karyotype. On univariate analysis, patients with more than or equal to 2 aberrations, 14q alterations, and TP53 deletions had the shortest survival; 7q deletion did not affect survival. On multivariate analysis, cytogenetic aberrations did not retain prognostic significance; the parameters negatively affecting survival were hemoglobin and age. In conclusion, the cytogenetic profile of SMZL is distinct from other B-cell lymphomas. Complexity of the karyotype, 14q aberrations, and TP53 deletions are poor prognostic indicators and may be considered together with other clinicobiologic parameters to ascertain the prognosis of SMZL.

Description: Mantle cell lymphoma (MCL) is characterized by the t(11;14)(q13;q32) translocation resulting in overexpression of cyclin D1. However, a small subset of cyclin D1− MCL has been recognized, and approximately one-half of them harbor CCND2 translocations while the primary event in cyclin D1−/D2− MCL remains elusive. To identify other potential mechanisms driving MCL pathogenesis, we investigated 56 cyclin D1−/SOX11+ MCL by fluorescence in situ hybridization (FISH), whole-genome/exome sequencing, and gene-expression and copy-number arrays. FISH with break-apart probes identified CCND2 rearrangements in 39 cases (70%) but not CCND3 rearrangements. We analyzed 3 of these negative cases by whole-genome/exome sequencing and identified IGK (n = 2) and IGL (n = 1) enhancer hijackings near CCND3 that were associated with cyclin D3 overexpression. By specific FISH probes, including the IGK enhancer region, we detected 10 additional cryptic IGK juxtapositions to CCND3 (6 cases) and CCND2 (4 cases) in MCL that overexpressed, respectively, these cyclins. A minor subset of 4 cyclin D1− MCL cases lacked cyclin D rearrangements and showed upregulation of CCNE1 and CCNE2. These cases had blastoid morphology, high genomic complexity, and CDKN2A and RB1 deletions. Both genomic and gene-expression profiles of cyclin D1− MCL cases were indistinguishable from cyclin D1+ MCL. In conclusion, virtually all cyclin D1− MCLs carry CCND2/CCND3 rearrangements with immunoglobulin genes, including a novel IGK/L enhancer hijacking mechanism. A subset of cyclin D1−/D2−/D3− MCL with aggressive features has cyclin E dysregulation. Specific FISH probes may allow the molecular identification and diagnosis of cyclin D1− MCL.