In non-follicular lymphoproliferative disorders, IGH/BCL2-fusion is not restricted to chronic lymphocytic leukaemia

The many faces of nodal and splenic marginal zone lymphomas. A report of the 2022 EA4HP/SH lymphoma workshop

Session 3 of the lymphoma workshop of the XXI joint meeting of the European Association for Haematopathology and the Society for Hematopathology took place in Florence, Italy, on September 22, 2022. The topics of this session were splenic and nodal marginal zone lymphomas, transformation in marginal zone lymphomas, and pediatric nodal marginal zone lymphomas and their differential diagnosis as well as related entities. Forty-two cases in these categories were submitted to the workshop, including splenic lymphomas (marginal zone and diffuse red pulp lymphomas), transformed marginal zone lymphomas (splenic and nodal), nodal marginal zone lymphomas with increased TFH-cells, and pediatric nodal marginal zone lymphomas. The case review highlighted some of the principal problems in the diagnosis of marginal zone lymphomas, including the difficulties in the distinction between splenic marginal zone lymphoma, splenic diffuse red pulp lymphoma, and hairy cell leukemia variant/splenic B-cell lymphoma with prominent nucleoli which requires integration of clinical features, immunophenotype, and morphology in blood, bone marrow, and spleen; cases of marginal zone lymphoma with markedly increased TFH-cells, simulating a T-cell lymphoma, where molecular studies (clonality and mutation detection) can help to establish the final diagnosis; the criteria for transformation of marginal zone lymphomas, which are still unclear and might require the integration of morphological and molecular data; the concept of an overlapping spectrum between pediatric nodal marginal zone lymphoma and pediatric-type follicular lymphoma; and the distinction between pediatric nodal marginal zone lymphoma and "atypical" marginal zone hyperplasia, where molecular studies are mandatory to correctly classify cases.

Divergent evolution of metachronous follicular lymphoma and extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue from a common precursor

The translocation t(14;18)(q32:q21)/IGH::BCL2 occurs at the pre-B stage of B-cell development in the bone marrow and is insufficient for malignant transformation, although it leads to the formation of in situ follicular B-cell neoplasia (ISFN). Despite that, the translocation is the genetic hallmark of follicular lymphoma (FL), it occurs infrequently in metachronous/synchronous lymphomas, including extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (EMZL), mantle cell lymphoma, and Hodgkin's lymphoma. In each of these scenarios, the two lymphomas often appear to be clonally related by analyses of IGH::BCL2 and/or rearranged IG genes. However, it remains largely unknown whether one lymphoma originates from the other or they develop independently. We studied five cases of metachronous EMZL and FL. In four cases, the two lymphomas were clonally related, as shown by identical IGH::BCL2 and/or rearranged IG genes or shared mutations. There were common and unique mutations between the paired EMZL and FL, indicating that they developed independently from a common premalignant cell population, harbouring IGH::BCL2 in three cases. Furthermore, case 1 presented with three metachronous FLs, and all of them originated from a common precursor cell population via divergent evolution. Our findings highlight the multi-malignant potential of IGH::BCL2-positive B-cells. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

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.

IGH Translocations in Chinese Patients With Chronic Lymphocytic Leukemia: Clinicopathologic Characteristics and Genetic Profile

Immunoglobulin heavy chain translocations (IGH-t) have occasionally been reported in Chinese patients with chronic lymphocytic leukemia (CLL). The objective of the present study was to identify the clinicopathologic features of patients with IGH-t CLL and compare them with those of patients with non-IGH-t CLL. We performed fluorescence in situ hybridization (FISH) based on a routine CLL prognostic FISH panel using IGH, IGH-BCL2, BCL3, IGH-CMYC, and BCL6 FISH probes. Furthermore, we retrospectively evaluated the clinical features of 138 newly diagnosed CLL patients via chromosome banding analysis (CBA), FISH, and targeted next-generation sequencing. IGH-t was identified in 25 patients (18.1%). Patients with IGH-t CLL had lower flow scores than those with non-IGH-t CLL. The most frequent translocation was t(14;18) (10 patients), followed by t(14;19) (3 patients), and t(2;14)(p13;q32), t(7;14)(q21.2;q12), t(9;14)(p13;q32) (3 patients). The remaining nine patients included three with abnormal karyotypes without translocation involving 14q32, four with a normal karyotype, and two who failed CBA. The most frequently concomitant FISH-detected aberrations were 13q deletion, followed by +12 and TP53 deletion, while one case involved ATM deletion. Complex karyotypes were detected in five patients with IGH-t CLL, in whom all partner genes were non-BCL2. Available mutational information indicated that KMT2D mutation was the most frequent mutation among tested 70 patients, while TP53 mutation was the most frequent mutation in the IGH-t group. Moreover, the IGH-t group had higher FBXW7 (P=0.014) and ATM (P=0.004) mutations than the non-IGH-t group, and this difference was statistically significant. Our study demonstrates that IGH-t is not uncommon among Chinese CLL patients, and that its partner genes are multiple. The gene mutational profile of the IGH-t group was distinct from that of the non-IGH-t group, and the concomitant chromosomal abnormalities within the IGH-t CLL group differed. Thus, identification of IGH-t and its partner genes in CLL patients may help further refine risk stratification and strengthen the accurate management in CLL patients.

A novel diagnostic approach for the classification of small B-cell lymphoid neoplasms based on the NanoString platform

Small B-cell lymphoid neoplasms (SBCLNs) are a heterogeneous group of diseases characterized by malignant clonal proliferation of mature B-cells. However, the classification of SBCLNs remains a challenge, especially in cases where histopathological analysis is unavailable or those with atypical laboratory findings or equivocal pathologic data. In this study, gene expression profiling of 1039 samples from 27 gene expression omnibus (GEO) datasets was first investigated to select highly and differentially expressed genes among SBCLNs. Samples from 57 SBCLN cases and 102 nonmalignant control samples were used to train a classifier using the NanoString platform. The classifier was built by employing a cascade binary classification method based on the random forest algorithm with 35 refined gene signatures. Cases were successively classified as chronic lymphocytic leukemia/small lymphocytic lymphoma, conventional mantle cell lymphoma, follicular lymphoma, leukemic non-nodal mantle cell lymphoma, marginal zone lymphoma, lymphoplasmacytic lymphoma/Waldenström's macroglobulinemia, and other undetermined. The classifier algorithm was then validated using an independent cohort of 197 patients with SBCLNs. Under the distribution of our validation cohort, the overall sensitivity and specificity of proposed algorithm model were >95%, respectively, for all the cases with tumor cell content greater than 0.72. Combined with additional genetic aberrations including IGH-BCL2 translocation, MYD88 L265P mutation, and BRAF V600E mutation, the optimal sensitivity and specificity were respectively found at 0.88 and 0.98. In conclusion, the established algorithm demonstrated to be an effective and valuable ancillary diagnostic approach for the sub-classification and pathologic investigation of SBCLN in daily practice.

[Chronic lymphocytic leukemia with t (14;18) (q32;q21) : report of eight cases and a literature review]

Objective: The study aimed to analyze the clinical features and prognosis of chronic lymphocytic leukemia (CLL) with t (14;18) (q32;q21) and conduct a literature review. Methods: The clinical data of 8 patients with CLL carrying t (14;18) (q32;q21) seen in Jiangsu Province Hospital from November 2009 to November 2019 were collected and analyzed. Results: Among the 8 cases, 7 were male and 1 was female. The median age at diagnosis was 70 years old. The immunophenotype score was 5 in 3 patients. 4 patients were scored 4 and the remaining one scored 3. The bone marrow histopathology showed the typical manifestation of CLL. Karyotype analysis showed that all the cases carried t (14;18) (q32;q21) in the stemline. The t (14;18) (q32;q21) showed as the sole abnormality in 3 cases, with +12 in 4, and with 13q- in 1 case. 13q- was found in another 3 patients by FISH. Immunoglobulin heavy chain gene (IGHV) mutation status was detected in 6 cases and all of them were mutated. None of them used IGHV3-21. Only 1 case harbored TP53 mutation and no TP53, SF3B1, NOTCH1, or MYD88 mutations were found in the remaining cases who underwent the relevant tests. At a median follow-up of 30.9 months, 1 case died. The remaining 7 cases survived and 3 of them have not reached the treatment indication. 4 patients who received chemotherapy or immunotherapy were stable. Conclusions: The t (14;18) (q32;q21) is rare in CLL and often accompanied by +12 and mutated IGHV. CLL with t (14; 18) (q32; q21) tends to have a good prognosis.

An unusual case of chronic lymphocytic leukemia with trisomy 12 and t(14;18) and a favorable response to ibrutinib

Chronic lymphocytic leukemia (CLL) is the most common type of adult leukemia. Chromosomal abnormalities are reported to play important roles in CLL pathogenesis and evolution, including deletions of 11q, 13q, 17p, and trisomy12, that are frequently observed and have a known prognostic value. Furthermore, the mutational status of the IGHV gene was reported as an independent prognostic marker in CLL impacting the choice of therapy. We herein, report an unusual presentation of a Lebanese CLL patient with two cytogenetic abnormalities: trisomy 12 and t(14;18)(q32;q21), along with an unmutated IGHV, displaying a favorable response to ibrutinib with a maintained complete remission.

IGH translocations in chronic lymphocytic leukemia: Clinicopathologic features and clinical outcomes

The prevalence, clinicopathologic correlates, and outcomes of previously untreated chronic lymphocytic leukemia (CLL) patients with IGH-BCL2 and IGH-BCL3 translocations are not well known. Using the Mayo Clinic CLL database, we identified patients seen between March 1, 2002 and September 30, 2016 who had FISH testing performed within 3 years of CLL diagnosis. The prognostic profile, time to first therapy (TTT), and overall survival (OS) of patients with IGH-BCL2 and IGH-BCL3 translocation were compared to patients without these abnormalities (non-IGH group). Of 1684 patients who met the inclusion criteria, 38 (2.2%) had IGH-BCL2, and 16 (0.9%) had IGH-BCL3 translocation at diagnosis. Patients with IGH-BCL3 translocation were more likely to have high and very-high CLL-International Prognostic Index, compared to patients with IGH-BCL2 translocation and the non-IGH group. The 5-year probability of requiring therapy was significantly higher for IGH-BCL3 compared to IGH-BCL2 and non-IGH groups (84% vs 33% vs 29%, respectively, P < 0.0001). The 5-year OS was significantly shorter for IGH-BCL3 compared to IGH-BCL2 and non-IGH groups (45% vs 89% vs 86%, respectively, P < 0.0001). On multivariable analyses, IGH-BCL3 translocation was associated with a shorter TTT (hazard ratio [HR] = 2.7; P = 0.005) and shorter OS (HR = 5.5; P < 0.0001); IGH-BCL2 translocation did not impact TTT and OS. In conclusion, approximately 3% of all newly diagnosed CLL patients have either an IGH-BCL2 or IGH-BCL3 translocation. Patients with IGH-BCL3 translocations have a distinct prognostic profile and outcome. These results support the inclusion of an IGH probe during the routine evaluation of FISH abnormalities in newly diagnosed CLL.

t(14;18)(q32;q21) in chronic lymphocytic leukemia patients: Report of two cases and a literature review

The chromosomal abnormality t(14;18)(q32;q21) is most commonly associated with germinal center-derived B-cell lymphomas, particularly follicular lymphoma (FL). Generally, it is considered a hallmark of FL. The t(14;18)(q32;q21) translocation is rare in chronic lymphocytic leukemia (CLL) and its prognostic significance remains unclear. In the present study, two cases of CLL with t(14;18)(q32;q21) were diagnosed using conventional cytogenetic analysis and fluorescence in situ hybridization. Both patients presented with leukemia and the morphological features and immunophenotypes were typical of CLL. Case 2 underwent a further lymph node biopsy, which established a diagnosis of CD5^- CLL/small lymphocyte lymphoma. In addition to t(14;18)(q32;q21), trisomy 12 was identified in the same clone in Case 2. Both cases exhibited immunoglobulin heavy chain variable mutations, and heavy-chain variable region gene (VH) 4-39 and VH3-62 were used in Case 1 and Case 2, respectively. In addition, direct Sanger sequencing of exons 4-9 revealed that Case 2 harbored the tumor protein p53 mutation, c.829T>G. Both cases had indications for therapy. Case 1 responded well to chlorambucil treatment, and was still alive at the last follow-up. Conversely, Case 2 exhibited aggressive disease that appeared refractory to treatment, and eventually succumbed to the disease.

Issues in diagnosis of small B cell lymphoid neoplasms involving the bone marrow and peripheral blood. Report on the Bone Marrow Workshop of the XVIIth meeting of the European Association for Haematopathology and the Society for Hematopathology

Small B cell lymphoid neoplasms are the most common lymphoproliferative disorders involving peripheral blood (PB) and bone marrow (BM). The Bone Marrow Workshop (BMW) organized by the European Bone Marrow Working Group (EBMWG) of the European Association for Haematopathology (EAHP) during the XVIIth EAHP Meeting in Istanbul, October 2014, was dedicated to discussion of cases illustrating how the recent advances in immunophenotyping, molecular techniques and cytogenetics provide better understanding and classification of these entities. Submitted cases were grouped into following categories: (i) cases illustrating diagnostic difficulties in chronic lymphocytic leukaemia (CLL); (ii) cases of BM manifestations of small B cell lymphoid neoplasms other than CLL; (iii) transformation of small B cell lymphoid neoplasms in the BM; and (iv) multiclonality and composite lymphomas in the BM. This report summarizes presented cases and conclusions of the BMW and provides practical recommendations for classification of the BM manifestations of small B cell lymphoid neoplasms based on the current state of knowledge.

Immunoglobulin gene translocations in chronic lymphocytic leukemia: A report of 35 patients and review of the literature

Chronic lymphocytic leukemia (CLL) represents the most common hematological malignancy in Western countries, with a highly heterogeneous clinical course and prognosis. Translocations involving the immunoglobulin (IG) genes are regularly identified. From 2000 to 2014, we identified an IG gene translocation in 18 of the 396 patients investigated at diagnosis (4.6%) and in 17 of the 275 analyzed during follow-up (6.2%). A total of 4 patients in whom the IG translocation was identified at follow-up did not carry the translocation at diagnosis. The IG heavy locus (IGH) was involved in 27 translocations (77.1%), the IG κ locus (IGK) in 1 (2.9%) and the IG λ locus (IGL) in 7 (20.0%). The chromosome band partners of the IG translocations were 18q21 in 16 cases (45.7%), 11q13 and 19q13 in 4 cases each (11.4% each), 8q24 in 3 cases (8.6%), 7q21 in 2 cases (5.7%), whereas 6 other bands were involved once (2.9% each). At present, 35 partner chromosomal bands have been described, but the partner gene has solely been identified in 10 translocations. CLL associated with IG gene translocations is characterized by atypical cell morphology, including plasmacytoid characteristics, and the propensity of being enriched in prolymphocytes. The IG heavy chain variable region (IGHV) mutational status varies between translocations, those with unmutated IGHV presumably involving cells at an earlier stage of B-cell lineage. All the partner genes thus far identified are involved in the control of cell proliferation and/or apoptosis. The translocated partner gene becomes transcriptionally deregulated as a consequence of its transposition into the IG locus. With the exception of t(14;18)(q32;q21) and its variants, prognosis appears to be poor for the other translocations. Therefore, searching for translocations involving not only IGH, but also IGL and IGK, by banding and molecular cytogenetics is required. Furthermore, it is important to identify the partner gene to ensure the patients receive the optimal treatment.

miRs-138 and -424 control palmitoylation-dependent CD95-mediated cell death by targeting acyl protein thioesterases 1 and 2 in CLL

Resistance toward CD95-mediated apoptosis is a hallmark of many different malignancies, as it is known from primary chronic lymphocytic leukemia (CLL) cells. Previously, we could show that miR-138 and -424 are downregulated in CLL cells. Here, we identified 2 new target genes, namely acyl protein thioesterase (APT) 1 and 2, which are under control of both miRs and thereby significantly overexpressed in CLL cells. APTs are the only enzymes known to promote depalmitoylation. Indeed, membrane proteins are significantly less palmitoylated in CLL cells compared with normal B cells. We identified APTs to directly interact with CD95 to promote depalmitoylation, thus impairing apoptosis mediated through CD95. Specific inhibition of APTs by siRNAs, treatment with miRs-138/-424, and pharmacologic approaches restore CD95-mediated apoptosis in CLL cells and other cancer cells, pointing to an important regulatory role of APTs in CD95 apoptosis. The identification of the depalmitoylation reaction of CD95 by APTs as a microRNA (miRNA) target provides a novel molecular mechanism for how malignant cells escape from CD95-mediated apoptosis. Here, we introduce palmitoylation as a novel posttranslational modification in CLL, which might impact on localization, mobility, and function of molecules, survival signaling, and migration.

Chronic Lymphocytic Leukemia with t(14;18)(q32;q21) As a Sole Cytogenetic Abnormality

BACKGROUND

Chronic lymphocytic leukemia (CLL) is the most common leukemia in adults. The chromosomal abnormality t(14;18)(q32;q21) is most commonly associated with neoplasms of a follicular center cell origin. However, t(14;18) has also been reported in rare cases of CLL.

OBJECTIVE

We describe the clinicopathologic, immunophenotypic, conventional, and molecular cytogenetic features of two rare cases proven to be CLL morphologically and immunologically in which t(14;18) was found as the sole cytogenetic abnormality.

METHODS

Morphologic, flow cytometric analysis and molecular cytogenetic of peripheral blood and/or bone marrow samples were analyzed.

RESULTS

Cytomorphologically, the cells were small mature lymphocytes without any findings that had characteristics of follicular lymphoma (FL) such as indented or clefted nuclei. Immunologic findings were characteristic of typical CLL without expression of CD10. A cytogenetic study revealed the two cases of CLL carrying t(14;18)(q32;q21).

CONCLUSION

We concluded that CLL with t(14;18) is rare and should be differentiated from FL as the therapy is highly diverse between both diseases. Using immunoglobulin heavy chain gene (IGH) probes are important in the workup of patients with suspected CLL and suggest that the IGH probe should be used routinely in all CLL fluorescence in situ hybridization (FISH) panels.

Oral follicular lymphomas. A short report of 8 cases with assessment of the IGH/BCL2 gene fusion with fluorescence in situ hybridization

OBJECTIVE

To present the clinicopathologic features and confirm the presence of the IGH/BCL2 gene fusion in an oral follicular lymphoma (OFL) series.

STUDY DESIGN

Cases of OFLs were retrieved from a data base of non-Hodgkin lymphomas (NHL). Fluorescence in situ hybridization (FISH) was performed to confirm the IGH/BCL2 fusion.

RESULTS

Eight (8.7%) of 92 NHL were OFLs. Six (75%) patients were male and two female (mean age: 73.4 ± 14.8). The most frequent site was the palate. Five of the 8 patients are alive and without disease. Five (three grade 1 and two grade 2) of six successfully hybridized cases revealed the IGH/BCL2 gene fusion. The sixth case, a grade 3 follicular lymphoma (FL), demonstrated multiple BCL2 signals without IGH/BCL2 fusion.

CONCLUSIONS

OFLs exhibit an indolent clinical behavior. In the present study, 5/6 cases in which FISH was successful had an IGH/BCL2 fusion as would result from the t(14; 18)(q32; q21) translocation commonly seen in FL of extraoral sites.

Genome-wide association study identifies multiple risk loci for chronic lymphocytic leukemia

Genome-wide association studies (GWAS) have previously identified 13 loci associated with risk of chronic lymphocytic leukemia or small lymphocytic lymphoma (CLL). To identify additional CLL susceptibility loci, we conducted the largest meta-analysis for CLL thus far, including four GWAS with a total of 3,100 individuals with CLL (cases) and 7,667 controls. In the meta-analysis, we identified ten independent associated SNPs in nine new loci at 10q23.31 (ACTA2 or FAS (ACTA2/FAS), P=1.22×10(-14)), 18q21.33 (BCL2, P=7.76×10(-11)), 11p15.5 (C11orf21, P=2.15×10(-10)), 4q25 (LEF1, P=4.24×10(-10)), 2q33.1 (CASP10 or CASP8 (CASP10/CASP8), P=2.50×10(-9)), 9p21.3 (CDKN2B-AS1, P=1.27×10(-8)), 18q21.32 (PMAIP1, P=2.51×10(-8)), 15q15.1 (BMF, P=2.71×10(-10)) and 2p22.2 (QPCT, P=1.68×10(-8)), as well as an independent signal at an established locus (2q13, ACOXL, P=2.08×10(-18)). We also found evidence for two additional promising loci below genome-wide significance at 8q22.3 (ODF1, P=5.40×10(-8)) and 5p15.33 (TERT, P=1.92×10(-7)). Although further studies are required, the proximity of several of these loci to genes involved in apoptosis suggests a plausible underlying biological mechanism.

Nodal and leukemic small B-cell neoplasms

The small B-cell neoplasms represent some of the most frequently encountered lymphoproliferative disorders in routine surgical pathology practice. This report reviews the current diagnostic criteria for classifying small B-cell neoplasms and distinguishing them from newly recognized precursor conditions that do not appear to represent overt lymphomas. Newly available immunohistochemical stains and molecular studies that may assist in the diagnosis and classification of these neoplasms are also discussed.

Chronic lymphocytic leukemia with t(14;18)(q32;q21)

The t(14;18)(q32;q21) is a cytogenetic hallmark of follicular lymphoma and also occurs in approximately 20% of diffuse large B-cell lymphomas of follicle center cell origin. Relatively few cases of chronic lymphocytic leukemia/small lymphocytic lymphoma with t(14;18) have been reported previously. We report the clinicopathologic, cytogenetic, and molecular genetic features of 12 patients with chronic lymphocytic leukemia associated with t(14;18). There were 9 men and 3 women, with a median age of 51 years at diagnosis. To date, 11 patients have required chemotherapy, 6 before coming to our institution. At last follow-up, 5 patients have died of disease. Karyotypic analysis showed that 10 cases had t(14;18) in the stemline and 2 cases in the sideline; t(14;18) was the sole abnormality in the stemline in 2 cases. In 11 cases, other abnormalities were identified in the stemline or sidelines, most commonly trisomy 12 in 6 cases. Trisomy 12 was associated with atypical morphology and immunophenotype. Of 8 cases tested, 7 showed somatically mutated immunoglobulin heavy chain variable region genes. We conclude that the t(14;18) in chronic lymphocytic leukemia is associated with relatively young age at diagnosis, mutated immunoglobulin heavy chain variable region genes, and a clinical course that usually requires chemotherapy. The cytogenetic findings, in particular, t(14;18) in the stemline in 10 cases and as the sole karyotypic abnormality in 2 cases, suggest that t(14;18) is an early pathogenetic event in this small subset of chronic lymphocytic leukemia cases.