CD23 expression in mantle cell lymphoma is associated with CD200 expression, leukemic non-nodal form, and a better prognosis

CD23 expression in lymphoplasmacytic lymphoma: Clinical-pathological and biological correlations

AIMS

The diagnosis of lymphoplasmacytic lymphoma (LPL) in the bone marrow (BM) is challenged by aberrant phenotypes and by overlapping histological features with marginal zone lymphoma (MZL). To address these issues, we (i) assessed LPL immunophenotype on a large series of BM samples, (ii) drew possible correlations between LPL phenotype and clinical/molecular data and (iii) investigated the role of new phenotypical markers in the differential diagnosis between LPL and MZL.

MATERIALS AND METHODS

The study retrospectively considered 81 clinically annotated LPL diagnosed at Padua University Hospital (Padua, Italy) during a 5-year period. BM findings were correlated with clinical laboratory findings and with MYD88 and CXCR4 mutational status. The obtained results were compared with a series of 77 MZL in the BM, including 46 splenic MZL (SMZL), 14 nodal MZL (NMZL) and 17 extra-nodal MZL (EMZL).

RESULTS

The LPL cohort included 52 males and 29 females (median age at diagnosis = 71 years). Aberrant CD10 and CD5 positivity was documented in 3 of 81 (3.7%) and 13 of 81 (16.1%) cases, respectively. CD23 positivity occurred in 56 of 81 (69.1%) cases, being usually partial/focal. CD23 expression did not correlate with any specific clinical-pathological parameter. Comparison with SMZL, NMZL and EMZL highlighted less frequent splenomegaly, higher serum paraprotein, higher CD23 expression and fewer follicular dendritic cell networks in LPL. A combined clinical-pathological score supported the differential diagnosis between LPL and MZL of any type. The highest diagnostic yield was obtained for the differential diagnosis between LPL and SMZL.

CONCLUSIONS

Partial positivity for CD23 is a common feature of LPL in the BM. Together with other clinical and histological parameters, CD23 expression supports the differential diagnosis between LPL and MZL.

Cyclin D1-negative mantle cell lymphoma

Cyclin D1-negative mantle cell lymphoma (MCL) is regarded as a B-cell neoplasm that has morphologic and immunophenotypic findings indistinguishable from typical MCL. These neoplasms lack cyclin D1 overexpression by immunohistochemistry and t(11;14)(q13;q32)/IGH::CCND1. Since cyclin D1-negative MCL was first recognized by gene expression profiling in 2003, there has been diagnostic confusion regarding this entity, mostly attributable to a lack of diagnostic tools to recognize these neoplasms in most clinical laboratories. Accumulated data show that most cyclin D1-negative MCL cases harbor CCND2 or CCND3 translocation with a variety of gene partners. In this review, the concept of cyclin D1-negative MCL is discussed in chronological order to further our understanding of this entity. We then discuss currently available diagnostic approaches and we conclude with future directions. We also suggest that the more specific terms CCND2-rearranged MCL or CCND3-rearranged MCL be used for neoplasms in which the rearranged gene is known, and that we reserve the term cyclin D1-negative MCL for neoplasms in which the rearranged gene in unknown.

SOX11+ Large B-Cell Neoplasms: Cyclin D1-Negative Blastoid/Pleomorphic Mantle Cell Lymphoma or Large B-Cell Lymphoma?

Large or blastoid B-cell neoplasms that are SOX11+ are a diagnostic dilemma and raise a differential diagnosis of cyclin D1-negative blastoid/pleomorphic mantle cell lymphoma (MCL) versus diffuse large B-cell lymphoma (DLBCL) or blastoid high-grade B-cell lymphoma (HGBL) with aberrant SOX11 expression. Here we report a study cohort of 13 SOX11+ large/blastoid B-cell neoplasms. Fluorescence in situ hybridization analysis was negative for CCND1 rearrangement in all 13 cases; 1 of 8 (12.5%) cases tested showed CCND2 rearrangement and 2 (25%) cases had extracopies of CCND2. Gene expression profiling showed that the study group had a gene expression signature similar to cyclin D1+ blastoid/pleomorphic MCL but different from DLBCL. Principal component analysis revealed that the cohort cases overlapped with cyclin D1+ blastoid/pleomorphic MCL but had minimal overlap with DLBCL. All patients in the cohort had clinicopathologic features similar to those reported for patients with cyclin D1+ MCL. We also performed a survey of SOX11 expression in a group of 85 cases of DLBCL and 24 cases of blastoid HGBL. SOX11 expression showed a 100% specificity and positive predictive value for the diagnosis of MCL. Overall, the results support the conclusion that large or blastoid B-cell neoplasms that are positive for SOX11 are best classified as cyclin D1-negative blastoid/pleomorphic MCL, and not as DLBCL or blastoid HGBL. We also conclude that SOX11 is a specific marker for the diagnosis of MCL, including cyclin D1-negative blastoid/pleomorphic MCL cases and should be performed routinely on blastoid/large B-cell neoplasms to help identify potential cases of cyclin D1-negative blastoid/pleomorphic MCL.

[CD23 positive, BCL2 rearrangement-negative germinal centre lymphomas]

Acknowledgeing that the group of follicular lymphomas is to be regarded as very heterogeneous, a group of follicular lymphomas has been delineated in recent years that was characterised by an often diffuse growth (without formation of evident follicular structures) as well as expression of CD23 in the lymphoma cells and the absence of the classic BCL2 translocation. Further characteristics are a preferred inguinal localisation of the lymphomas and a localised stage with a good prognosis. Genetically, this lymphoma group is characterised by a high rate of either STAT6 or SOCS1 mutations.The ICC classification took this development into account by introducing the provisional entity CD23 positive, BCL2 rearrangement-negative germinal centre lymphoma. Further studies must now show how exactly this entity can be defined (combination of morphology, immunohistochemical phenotype, focus on genetic alterations) in order to pave the way towards a uniform classification and a better clinical characterisation of these cases - especially with regard to possible new therapeutic treatment options.

PAX5 aberrant expression incorporated in MIPI-SP risk scoring system exhibits additive value in mantle cell lymphoma

Mantle cell lymphoma (MCL) is a subtype of non-Hodgkin lymphoma with highly heterogeneous clinical courses. Paired-box 5 (PAX5), the regulator of B cell differentiation and growth, is abnormally expressed in several types of cancers. Herein, we explored the prognostic value of PAX5 in MCL by comprehensively analyzing the clinical features and laboratory data of 82 MCL cases. PAX5 positivity was associated with shorter overall survival (OS; p = 0.011) and was identified as an independent prognostic factor in MCL patients. The elevated β2-MG (p = 0.027) and advanced Mantle Cell Lymphoma International Prognostic Index (MIPI) score (p = 0.014) were related to positive PAX5 expression. The MIPI-SP risk scoring system was established and exhibited a superior prognostic value for OS depending on an area under the curve (AUC) of 0.770 (95% CI, 0.658-0.881) than MIPI score. Bioinformatic analysis of PAX5-related genes supported the mechanistic roles of PAX5 in MCL. This study provides insight into the potential role of PAX5 in MCL, and the novel risk scoring system MIPI-SP optimizes the risk stratification and facilitates prognosis evaluation in MCL patients. KEY MESSAGES: • Paired-box 5 positivity indicated adverse prognosis in mantle cell lymphoma patients. • Positive PAX5 expression was related to MIPI score and β2-MG in MCL patients. • MIPI-SP risk scoring system has superior prognostic value than MIPI score in MCL.

How I manage mantle cell lymphoma: indolent versus aggressive disease

Mantle cell lymphoma (MCL) is a mature B-cell lymphoma with a variable clinical course and historically poor prognosis. Management is challenging in part due to the heterogeneity of the disease course, with indolent and aggressive subtypes now well recognised. Indolent MCL is often characterised by a leukaemic presentation, SOX11 negativity and low proliferation index (Ki-67). Aggressive MCL is characterised by rapid onset widespread lymphadenopathy, extra-nodal involvement, blastoid or pleomorphic histology and high Ki-67. Tumour protein p53 (TP53) aberrations in aggressive MCL are recognised with clear negative impact on survival. Until recently, trials have not addressed these specific subtypes separately. With the increasing availability of targeted novel agents and cellular therapies, the treatment landscape is constantly evolving. In this review, we describe the clinical presentation, biological factors, and specific management considerations of both indolent and aggressive MCL and discuss current and potential future evidence which may help move to a more personalised approach.

Chronic lymphocytic leukaemia/small lymphocytic lymphoma and mantle cell lymphoma: from early lesions to transformation

The International Clinical Advisory Committee reviewed advances in our understanding of the clinicopathologic and biologic features of chronic lymphocytic leukaemia/small lymphocytic lymphoma, B-cell prolymphocytic leukaemia, and mantle cell lymphoma since the revised 4th edition of the WHO Classification of Tumours of the Haematopoietic and Lymphoid Tissues. Discussions amongst pathologists, clinicians, and molecular geneticists around these diseases focussed on incorporating new knowledge into the next classification system. In this manuscript, we review these disease entities and incorporate results of these deliberations, including advances in our understanding of early lesions and transformation.

Identification of Six Diagnostic Biomarkers for Chronic Lymphocytic Leukemia Based on Machine Learning Algorithms

BACKGROUND

Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in adults. Thus, novel reliable biomarkers need to be further explored to increase diagnostic, therapeutic, and prognostic effectiveness.

METHODS

Six datasets containing CLL and control samples were downloaded from the Gene Expression Omnibus database. Differential gene expression analysis, weighted gene coexpression network analysis (WGCNA), and the least absolute shrinkage and selection operator (LASSO) regression were applied to identify potential diagnostic biomarkers for CLL using R software. The diagnostic performance of the hub genes was then measured by the receiver operating characteristic (ROC) curve analysis. Functional analysis was implemented to uncover the underlying mechanisms. Additionally, correlation analysis was performed to assess the relationship between the hub genes and immunity characteristics.

RESULTS

A total number of 47 differentially expressed genes (DEGs) and 25 candidate hub genes were extracted through differential gene expression analysis and WGCNA, respectively. Based on the 14 overlapped genes between the DEGs and the candidate hub genes, LASSO regression analysis was used, which identified a final number of six hub genes as potential biomarkers for CLL: ABCA6, CCDC88A, PMEPA1, EBF1, FILIP1L, and TEAD2. The ROC curves of the six genes showed reliable predictive ability in the training and validation cohorts, with all area under the curve (AUC) values over 0.80. Functional analysis revealed an abnormal immune status in the CLL patients. A significant correlation was found between the hub genes and the immune-related pathways, indicating a possible tight connection between the hub genes and tumor immunity in CLL.

CONCLUSION

This study was based on machine learning algorithms, and we identified six genes that could be possible CLL markers, which may be involved in CLL pathogenesis and progression through immune-related signal pathways.

Mantle cell lymphoma negative for t(11,14) involving the kidneys: a case report

Background

Mantle cell lymphoma is the rarest subtype of non-Hodgkin’s lymphoma. It can exhibit diverse extranodal manifestations. However, renal involvement is uncommon, and if it occurs, it usually only gets detected postmortem. There are several mechanisms by which mantle cell lymphoma can damage the kidneys. Renal failure is a potential complication, and prompt evaluation and diagnosis are critical steps to prevent long-term complications.

Case presentation

We present the case of a 75-year-old non-Hispanic White male with past medical history significant for hypertension and dyslipidemia, presenting with fever, weight loss, and night sweats. Work-up showed markedly elevated white blood cells, multiple enlarged lymph nodes, and a kidney mass. The patient was diagnosed with mantle cell lymphoma with kidney involvement confirmed with a kidney biopsy. His disease was positive for cyclin D1 overexpression despite t(11; 14) absence. The patient received six cycles of alternating vincristine, rituximab, cyclophosphamide, doxorubicin, and prednisone then dexamethasone, high-dose cytarabine, and oxaliplatin, after which he was maintained on ibrutinib and rituximab, with resolution of symptoms and disease regression.

Conclusion

We present a case of a rare presentation of Mantle cell lymphoma while describing the clinical presentation and diagnostic and treatment approaches. This case report can assist physicians in the clinical work-up and treatment of patients with similar diagnosis or presentation.

Mantle Cell Lymphoma with Chronic Lymphocytic Leukemia-Like Features: A Diagnostic Mimic and Pitfall

Mantle cell lymphoma (MCL) is a mature B-cell neoplasm characterized by t(11;14)(q13;q32) and cyclin D1 overexpression in >95% of cases. Classic MCL cases are composed of a monotonous population of small to medium-sized lymphocytes with irregular nuclear contours that are positive for cyclin D1 and SOX11, and negative for CD23 and CD200. By contrast, occasional MCL cases express CD23 and CD200 but lack of SOX11, and morphologically and immunophenotypically resemble chronic lymphocytic leukemia (CLL), termed as CLL-like MCL in this study. These neoplasms pose a diagnostic challenge and easy to be diagnosed as CLL in daily practice. We studied 14 cases of CLL-like MCL to define their clinicopathologic features and compared them with 33 traditional CLL cases. There were 8 men and 6 women with a median age of 62 years (range, 44-80). Compared with CLL, patients with CLL-like MCL have lower levels of peripheral blood and bone marrow involvement, and more frequently had mutated IGHV. Immunophenotypically, CLL-like MCL often showed moderate to bright expression of B-cell antigens and surface immunoglobulin light chain, dim and partial expression of CD23 and CD200, infrequent CD43 positivity, and lack of LEF1. The overall survival of patients with CLL-like MCL was similar to that of CLL patients. In conclusion, CD23+, CD200+, and SOX11-negative MCL closely resemble CLL, both clinically and pathologically, including a similar indolent clinical course. They may pose a diagnostic challenge. However, patients with CLL-like MCL also have distinctive immunophenotypic features that are useful to distinguish these neoplasms from CLL.

Mantle cell lymphoma involving tonsils: a clinicopathologic study of 83 cases

We report 83 cases of mantle cell lymphoma (MCL) involving the tonsil as initial manifestation (IM). The median age at the time of tonsillar involvement was 58 years (range, 35-79 years). Most (85%) patients presented similar to acute tonsillitis. Lymphadenopathy (84%) and advanced stage of disease (81%) were frequent. With a median follow-up of 6.1 years (range, 0.5-18.4 years), the median overall survival (OS) was 11.3 years for all patients. Cases with classic MCL morphology demonstrated a superior OS (median OS: 11.7 years versus 7.8 years for aggressive morphology, P = 0.0361). Approximately 20% of patients had limited stage of disease, and they had excellent outcomes (median OS: not reached versus 11.3 years for advanced-stage MCL, P = 0.0479). All the patients were alive after a median follow-up of 6.6 years (range, 1-16.2 years). There were no differences in relapse-free survival in morphology and stage (P > 0.05). When tonsils were involved by relapsed MCL, patients less commonly had acute tonsillitis-like symptoms, lymphadenopathy, and advanced stage of disease compared to MCL as IM. Patients in the relapse group had poorer OS than patients in the IM group from the time of tonsillar involvement by MCL to the date of death or last follow-up (7.8 versus 11.7 years, P = 0.003). Compared with a group of 93 patients whose initial biopsy specimen was a lymph node, patients whose initial biopsy specimen was tonsil had similar OS (11.7 versus 8.8 years, P = 0.1764). However, patients with tonsillar MCL more commonly had limited stage disease (19% versus 8%, P = 0.0385) and a low-risk Mantle Cell Lymphoma International Prognostic Index score (71% versus 47%, P = 0.0025).

Detailed characterization of the transcriptome of single B cells in mantle cell lymphoma suggesting a potential use for SOX4

Mantle cell lymphoma (MCL) is a malignancy arising from naive B lymphocytes with common bone marrow (BM) involvement. Although t(11;14) is a primary event in MCL development, the highly diverse molecular etiology and causal genomic events are still being explored. We investigated the transcriptome of CD19⁺ BM cells from eight MCL patients at single-cell level. The transcriptomes revealed marked heterogeneity across patients, while general homogeneity and clonal continuity was observed within the patients with no clear evidence of subclonal involvement. All patients were SOX11⁺CCND1⁺CD20⁺. Despite monotypic surface immunoglobulin (Ig) κ or λ protein expression in MCL, 10.9% of the SOX11 + malignant cells expressed both light chain transcripts. The early lymphocyte transcription factor SOX4 was expressed in a fraction of SOX11 + cells in two patients and co-expressed with the precursor lymphoblastic marker, FAT1, in a blastoid case, suggesting a potential prognostic role. Additionally, SOX4 was found to identify non-malignant SOX11^– pro-/pre-B cell populations. Altogether, the observed expression of markers such as SOX4, CD27, IgA and IgG in the SOX11⁺ MCL cells, may suggest that the malignant cells are not fixed in the differentiation state of naïve mature B cells, but instead the patients carry B lymphocytes of different differentiation stages.

Clinicopathological and Immunohistochemical Profile of Mantle Cell Lymphoma: An Institutional Experience

Introduction

Mantle cell lymphoma (MCL) is a biologically aggressive B-cell non-Hodgkin lymphoma (NHL) with distinctive morphologic, immunophenotypic, and molecular characteristics. Differentiation from other chronic lymphoproliferative disorders is essential for prognostication.

Aim

This paper aims to study the clinicopathological features of MCL with emphasis on immunohistochemical features and disease correlation.

Method

To do so, clinicopathological characteristics from 21 cases of MCL (14 males, seven females, M:F=2:1) diagnosed in the last five years i.e. 2015 to 2020, were retrospectively reviewed and correlated with immunohistochemistry (IHC) data. Particularly those pertaining to cyclin D1, SRY-box transcription factor 11 (SOX11), cluster of differentiation (CD) 5, CD23, MIB E3 ubiquitin protein ligase 1 (MIB1), tumor protein 53 (TP53), c-myelocytomatosis oncogene product (c-MYC), multiple myeloma oncogene 1 (MUM1), mouse double minute 2 homolog (MDM2), and Epstein-Barr virus latent membrane protein 1 (EBV-LMP1) expression with its aberrations.

Observations

This study shows that MCL constituted 4.2% (21/500) of all NHLs with a mean age of 57.5 years (median 60 years, range 30 to 80 years). The disease was nodal in 19, and extranodal in the remaining two cases. 14 of 21 (67%) had generalized lymphadenopathy and 71% had bone marrow (BM) involvement. The nodal involvement was diffuse in 9/17 (53%), 8/21 (38%) had a blastoid morphology, and an in-situ MCL pattern was not seen in any of the cases selected for the study. Cyclin D1 immunoexpression correlated well with SOX11; CD5-negative in five cases; and CD23-positive in three cases. TP53 and c-MYC expression were noted in 17/19 (89.4%) and 8/17 (47%), respectively. MUM1 registered positive in six cases. None of the cases showed immunopositivity for MDM2 and EBV-LMP1.

Conclusion

In essence, this study indicates that morphological and immunophenotypic subclassification of mantle cell lymphoma with a wider panel of IHC markers is essential for understanding disease biology and better prognostication.

Leukemic Variant of Mantle Cell Lymphoma: Clinical Presentation and Management

PURPOSE OF REVIEW

This review summarizes the unique presentation and management of the leukemic variant of mantle cell lymphoma (LV-MCL, also referred to as non-nodal MCL) and highlights the biologic and clinical differentiation from classical mantle cell lymphoma (cMCL) in biomarker expression, clinical features, prognosis, disease course, and treatment.

RECENT FINDINGS

Several studies have evaluated the gene expression profile of mantle cell lymphoma, differentiating LV-MCL from cMCL. The typical immunophenotypic profile is CD5-positive, SOX 11-negative, CD23-low, CD200-low, and cyclin D1 overexpressed. LV-MCL commonly has mutated immunoglobulin heavy chain variable region genes. Data on treatment of LV-MCL is limited to retrospective analyses; the ideal treatment for these patients is unknown although many have a clinically indolent, asymptomatic presentation and often may be observed for an extended period without active treatment. LV-MCL is a clinically and biologically distinct entity. Clinically, it must be distinguished from chronic lymphocytic leukemia and cMCL. Future prospective, randomized clinical trials are required to optimize management, define the initial treatment, and appropriately sequence treatment modalities.

Progress in molecular feature of smoldering mantle cell lymphoma

Mantle cell lymphoma (MCL) is considered one of the most aggressive lymphoid tumors. However, it sometimes displays indolent behavior in patients and might not necessitate treatment at diagnosis; this has been described as "smoldering MCL" (SMCL). There are significant differences in the diagnosis, prognosis, molecular mechanisms and treatments of indolent MCL and classical MCL. In this review, we discuss the progress in understanding the molecular mechanism of indolent MCL to provide insights into the genomic nature of this entity. Reported findings of molecular features of indolent MCL include a low Ki-67 index, CD200 positivity, a low frequency of mutations in TP53, a lack of SOX11, normal arrangement and expression of MYC, IGHV mutations, differences from classical MCL by L-MCL16 assays and MCL35 assays, an unmutated P16 status, few defects in ATM, no NOTCH1/2 mutation, Amp 11q gene mutation, no chr9 deletion, microRNA upregulation/downregulation, and low expression of several genes that have been valued in recent years (SPEN, SMARCA4, RANBP2, KMT2C, NSD2, CARD11, FBXW7, BIRC3, KMT2D, CELSR3, TRAF2, MAP3K14, HNRNPH1, Del 9p and/or Del 9q, SP140 and PCDH10). Based on the above molecular characteristics, we may distinguish indolent MCL from classical MCL. If so, indolent MCL will not be overtreated, whereas the treatment of classical MCL will not be delayed.

MYC rearrangement but not extra MYC copies is an independent prognostic factor in patients with mantle cell lymphoma

Mantle cell lymphoma (MCL) with MYC rearrangement (MYC-R) is rare and little is known about the importance of MYC extra copies (EC) in the absence of MYC-R in MCL patients. This study includes 88 MCL patients with MYC tested by fluorescence in situ hybridization and/or conventional cytogenetics, including 27 with MYC-R, 21 with MYC-EC, and 40 with normal (NL) MYC. MCL patients with MYC-R more often had blastoid/pleomorphic morphology; a higher frequency of CD10, MYC, and simultaneous MYC and BCL2 expression; a higher level of MYC; and a higher Ki67 proliferation rate (p<0.05) than those without MYC-R. Although patients with MYC-R more frequently received aggressive chemotherapy (p=0.001), their overall survival (OS) was significantly shorter than those without MYC-R. Compared with patients with MYC/BCL2 double hit lymphoma (DHL), patients with MYC-R MCL had a similar OS but more commonly had bone marrow involvement, stage 4 disease, and a different immunophenotype. MCL patients with MYC-EC showed an OS intermediate between those with MYC-R and MYC-NL, either all or only blastoid/pleomorphic MCL patients included. Multivariate analysis showed that MYC-R, but not MYC-EC, had an independent and negative impact on OS. In conclusion, MYC-R but not MYC-EC showed a higher MYC expression and is an adverse prognostic factor for MCL patients. Although the OS of MCL patients with MYC-R is similar to that of MYC/BCL2 DHL patients, these groups have different clinicopathologic features supporting the retention of MCL with MYC-R in the category of MCL, as recommended in the revised World Health Organization classification.

Blastoid Mantle Cell Lymphoma

Blastoid and pleomorphic mantle cell lymphoma (MCL) are among the worst prognostic, aggressive histology, high-risk variants of MCL, and, in this article, they are presented as blastoid MCL. Blastoid MCL have not been systematically studied, probably due to their rarity. De novo blastoid MCLs have superior outcomes compared with transformed MCL. Compared with classic MCL, extranodal involvement (mainly skin, central nervous system), frequent relapses, and inferior responses to conventional chemoimmunotherapy, BTK inhibitors and venetoclax are frequent in blastoid MCL. KTE-X19 induces excellent response in blastoid MCL. Combinations with novel agents are actively investigated. This article presents a comprehensive review on blastoid MCL in 2020.

Differential diagnosis of chronic lymphocytic leukemia/small lymphocytic lymphoma and other indolent lymphomas, including mantle cell lymphoma

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) accounts for approximately 1% of all lymphomas in our department. In this article, we describe the differential diagnosis of CLL/SLL from other indolent lymphomas, with special reference to follicular lymphoma, marginal zone B-cell lymphoma, lymphoplasmacytic lymphoma, and mantle cell lymphoma, although the latter is considered to be aggressive. CLL/SLL often exhibits proliferation centers, similar to follicular lymphoma. Immunohistological examination can easily distinguish these two lymphomas. The most important characteristic of CLL/SLL is CD5 and CD23 positivity. Mantle cell lymphoma is also CD5-positive and there are some CD23-positive cases. Such cases should be carefully distinguished from CLL/SLL. Some marginal zone lymphomas are also positive for CD5 and such cases are often disseminated. Lymphoplasmacytic lymphoma should also be a differential diagnosis for CLL/SLL. It frequently demonstrates MYD88 L265P, which is a key differential finding. By immunohistological examination, the expression of lymphoid enhancer-binding factor 1 is specific for CLL/SLL and can be a good marker in the differential diagnosis.