CD10-positive mantle cell lymphoma: clinicopathologic and prognostic study of 30 cases

Large B-cell lymphoma with IRF4 rearrangement: a multi-centric study with focus on potential misleading phenotypes

Large B-cell lymphoma with IRF4 rearrangement (LBCL-IRF4) is a rare lymphoid neoplasm, usually occurring in the pediatric/young-adult age. Despite this, subsets of cases occur in elderly patients and express CD5, possibly entering the differential diagnosis with adult aggressive lymphomas, such as blastoid/pleomorphic mantle cell lymphoma (MCL-B/P). To better characterize the clinical-pathological features and differential diagnosis of LBCL-IRF4, we conducted a multi-centric study on 12 cases, focusing on CD5, Cyclin D1, and SOX11 expression. While most cases had typical presentation, adult-to-elderly age at diagnosis and unusual anatomic locations were reported in 3/12 (25.0%) and 2/12 (16.7%) patients, respectively. Histologically, CD5 was positive in 4/12 (33.3%) cases, Cyclin D1 was invariably negative, and SOX11 was weakly/partially expressed in 1/12 (8.3%) case. In conclusion, LBCL-IRF4 can have unconventional clinical presentations that may challenge its recognition. Although CD5 is frequently expressed, negativity for Cyclin D1 and SOX11 contributes to the differential diagnosis with MCL-B/P.

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.

Aggressive B-cell non-Hodgkin lymphomas: a report of the lymphoma workshop of the 20th meeting of the European Association for Haematopathology

Aggressive B-cell non-Hodgkin lymphomas are a heterogeneous group of diseases and our concepts are evolving as we learn more about their clinical, pathologic, molecular genetic features. Session IV of the 2020 EAHP Workshop covered aggressive, predominantly high-grade B-cell lymphomas, many that were difficult to classify. In this manuscript, we summarize the features of the submitted cases and highlight differential diagnostic difficulties. We specifically review issues related to high-grade B-cell lymphomas (HGBCLs) with MYC and BCL2 and/or BCL6 rearrangements including TdT expression in these cases, HGBCL, not otherwise specified, large B-cell lymphomas with IRF4 rearrangement, high-grade/large B-cell lymphomas with 11q aberration, Burkitt lymphoma, and pleomorphic mantle cell lymphoma. Since the workshop, the 5th edition of the WHO Classification for Haematolymphoid Tumours (WHO-HAEM5) and International Consensus Classification (ICC) 2022 were published. We endeavor to use the updated terminology.

Blastoid Variant of Mantle Cell Lymphoma with Extranodal Presentation and Aberrant CD10 Expression

Mantle cell lymphoma (MCL) constitutes 3%-10% of non-Hodgkin lymphoma and is characterized by t (11:14)(q13;q32). The common presentation is generalized lymphadenopathy with weight loss, infrequently night sweats, and fever. Among histological subtypes of MCL, the blastoid variant of MCL constitutes 10%-15% of all the cases. It is challenging to diagnose the blastoid variant of MCL based on its morphology alone as it mimics large B-cell lymphoma. Hence, the immunophenotyping and molecular studies aid in its correct diagnosis. We report an elderly man diagnosed with blastoid variant MCL. He presented with disseminated soft-tissue and subcutaneous nodules, and showed aberrant CD10 expression. Presentation of the extranodal site and aberrant CD10 expressions carries an overall poor prognosis. CD10-positive MCL can be mistaken for large B-cell lymphoma.

Testicular involvement in mantle cell lymphoma: An analysis of 16 patients

Mantle cell lymphoma (MCL) with testicular involvement is a rare presentation and only a few cases have been described in the literature. We present a case of MCL with testicular involvement and the first analysis of all previously reported cases assessing trends in immunohistochemical features, prognostic indicators, and survival. Our data suggest that among all MCL, testicular MCL is more likely to present with aggressive features: blastoid/pleomorphic morphology, high Ki-67 proliferative index, and CNS involvement. Testicular MCL is also associated with shorter overall survival.

A Push to Consider Mantle Cell Lymphoma in Adults with Leukemia/Lymphoma with Blastoid Morphology

Mantle cell lymphoma (MCL) is an intermediate-grade B-cell lymphoma, representing 2.8% of all non-Hodgkin lymphomas in the US. It is associated with t(11;14)(q13; q23), which leads to the overexpression of cyclin D1, consequently promoting cell proliferation. MCL usually expresses CD19, CD20, CD43, surface immunoglobulins, FMC7, BCL2, cyclin D1, CD5, and SOX11. Herein is a case of a 67-year-old male, referred to our facility with shortness of breath, anemia (hemoglobin of 5.3 g/dL), thrombocytopenia (12 × 109/L), and leukocytosis (283 × 109/L). A peripheral blood smear showed marked lymphocytosis with blastoid morphology. Morphologic examination of the bone marrow biopsy revealed a diffuse sheet of blastoid cells expressing CD20 and CD10, but without CD5 or cyclin D1. Given these features, a differential diagnosis of diffuse large B-cell lymphoma (DLBCL) with germinal center derivation, high-grade follicular lymphoma, and Burkitt lymphoma was considered, with the latter not favored due to morphology. Additional studies revealed positive SOX11, and fluorescence in situ hybridization (FISH) studies detected t(11;14). These additional studies supported diagnosis of the blastoid variant of MCL. In conclusion, we present a unique and challenging case of MCL without cyclin D1 or CD5, but with an expression of CD10 and SOX11, along with t(11;14). Pathologists should explicitly consider the blastoid variant of MCL when dealing with mature B-cell neoplasms with blastoid morphology in adults, and utilize a broad panel of ancillary studies, including FISH and SOX11.

19-color, 21-Antigen Single Tube for Efficient Evaluation of B- and T-cell Neoplasms

Non-Hodgkin lymphoma (NHL) is a heterogeneous disease, encompassing a wide variety of individually distinct neoplastic entities of mature B-, T-, and NK-cells. While they constitute a broad category, they are the most common hematologic malignancies in the world. The distinction between different neoplastic entities requires a multi-modal approach, such as flow cytometric immunophenotyping, which can exclude a neoplastic proliferation and help narrow the differential diagnosis. This article describes a flow cytometric test developed at Memorial Sloan Kettering Cancer Center to assess B-, T-, and NK-cells in a single tube, 21-antibody, 19-color assay. The assay can identify most B- and T-cell NHLs with high specificity and sensitivity and significantly narrow the differential when a specific diagnosis cannot be made. The basic protocol provides a detailed operational procedure for sample processing, staining, and cytometric acquisition. The support protocol provides typical steps and caveats for data analysis in lymphoproliferative disorders and in discriminating a variety of specific disease entities from each other and normal lymphoid populations. © 2023 Wiley Periodicals LLC. Basic Protocol: Processing, staining, and cytometric analysis of samples for B- and T-cell assessment Support Protocol: Analysis and interpretation of the B- and T-cell lymphocyte assay.

Unveiling the Prognostic Significance of BCL6+/CD10+ Mantle Cell Lymphoma: Meta-Analysis of Individual Patients and Systematic Review

Mantle cell lymphoma (MCL) is a type of non-Hodgkin lymphoma (NHL) characterized by a hallmark translocation of t (11; 14). CD10 negativity has been used to differentiate MCL from other NHL types; however, recently, there has been an increase in the number of reported cases of CD10-positive MCL. This warrants further investigation into this rarer immunophenotype and its clinical significance. BCL6, which is a master transcription factor for the regulation of cell proliferation and key oncogene in B cell lymphomagenesis, has been reported to have co-expression with CD10 in MCL. The clinical significance of this aberrant antigen expression remains unknown. We conducted a systematic review by searching four databases and selected five retrospective analyses and five case series. Two survival analyses were conducted to determine if BCL6 positivity conferred a survival difference: 1. BCL6+ vs. BCL6- MCL. 2. BCL6+/CD10+ vs. BCL6-/CD10+ MCL. Correlation analysis was conducted to determine if BCL6 positivity correlated with the Ki67 proliferation index (PI). Overall survival (OS) rates were performed by the Kaplan-Meier method and log-rank test. Our analyses revealed that BCL6+ MCL had significantly shorter overall survival (median OS: 14 months vs. 43 months; p = 0.01), BCL6+/CD10+ MCL had an inferior outcome vs. BCL6+/CD10- MCL (median OS: 20 months vs. 55 months p = 0.1828), BCL6+ MCL had significantly higher percentages of Ki67% (Ki67% difference: 24.29; p = 0.0094), and BCL6 positivity had a positive correlation with CD10+ status with an odds ratio 5.11 (2.49, 10.46; p = 0.0000286). Our analysis showed that BCL6 expression is correlated with CD10 positivity in MCL, and BCL6 expression demonstrated an inferior overall survival. The higher Ki67 PI in BCL6+ MCL compared to BCL6- MCL further supports the idea that the BCL6+ immunophenotype may have prognostic value in MCL. MCL management should consider incorporating prognostic scoring systems adjusted for BCL6 expression. Targeted therapies against BCL6 may offer potential therapeutic options for managing MCL with aberrant immunophenotypes.

Poly-lymphomatous Syndrome With Concurrent or Sequential Hodgkin and Non-Hodgkin lymphoma

INTRODUCTION

The development of Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) concurrently or sequentially in the same patient is a rare clinical scenario and can be labeled as a poly-lymphomatous syndrome (PLS).

METHODS

We report clinico-pathologic characteristics and survival outcomes of 7 such cases from our institution. In concurrent PLS, HL is present with NHL in the same location (composite PLS) or in separate locations (discordant PLS). Sequential presentations were seen with HL following NHL or vice versa (sequential PLS).

CONCLUSIONS

It is essential to perform adequate biopsies in supposedly relapsed or refractory settings to diagnose PLS. We suggest that the incidence of PLS is likely underestimated due to the under-utilization of repeat biopsies. In patients with concurrent PLS, the treatment should ideally cover both types of lymphoma with an emphasis on tailoring the treatment towards the more aggressive lymphoma. In patients with sequential PLS, the treatment should target the new lymphoma. Consolidation treatments such as autologous hematopoietic cell transplant should be considered when there is a component of relapsed cHL or aggressive NHL. Based on our experience, PLS does not appear to be associated with a poor prognosis. Further research is necessary for better understanding of the biology and management of PLS.

Clinicopathologic Features and Treatment of CD10-Positive Mantle Cell Lymphoma: A Case Report and Review of Literature

Mantle cell lymphoma (MCL) is a rare and aggressive non-Hodgkin’s B cell lymphoma characterized by the translocation t(11;14) (q13;32) and overexpression of CCND1. MCL is immunophenotypically identified as CD20⁺, CD5⁺, CyclinD1+, CD43⁺, CD10⁻, BCL6⁻, and CD23⁻. It is often distinguished from B cell lymphomas of germinal center cell origin by the absence of CD10 expression. Here we report the unique clinicopathologic features of a patient with CD10⁺ MCL with gastrointestinal involvement and review current literature identifying this unique immunophenotype.

Cooccurrence of CD10-Positive and CD10-Negative Mantle Cell Lymphoma Complicated With Central Nervous System Involvement Solely by CD10-Positive Population

The neoplastic cells of mantle cell lymphoma (MCL) usually express CD5 and not CD10. However, cases of MCL with aberrant expression of CD10 have been seldom reported. A 71-year-old man presented multiple lymphadenopathies with a bulky tumor of the abdomen. He received the biopsies from the left cervical lymph node and the duodenum. The former specimen showed MCL with CD5-positive and CD10-negative, but the latter showed MCL with CD5-positive and CD10-positive. After receiving induction therapy, he developed convulsions, and lymphoma cells expressing CD5-positive and CD10-positive were detected in cerebrospinal fluid (CSF). CD10-positive MCL has some significant clinical characteristics. And it shows worse overall survival compared with CD10-negative MCL when it has aggressive features such as blastoid and pleomorphic morphology, high-Ki-67 index, and high mantle cell lymphoma international prognostic index (MIPI). Therefore, physicians and pathologists must carefully discriminate against cases having this aberrant expression.

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.

CD5-negative blastoid variant mantle cell lymphoma: a diagnostic dilemma

We encountered two cases of CD5^- blastoid variant mantle cell lymphoma (MCL), prompting us to investigate the proportion of CD5 negativity in MCL and assess the diagnosis of aggressive MCL variants. Among 117 patients diagnosed with MCL, CD5 negativity was observed in 13% (13/104) of cases with classical MCL and 15% (2/13) of cases with blastoid/pleomorphic variant MCL. Of the aggressive MCL variant cases, tumor cells exhibited intermediate nuclear size and required differential diagnosis between blastoid variant and classical MCL in six patients, and classical MCL cells were found in the background of aggressive variant tumors or in other sites in six patients. Of 1534 patients with diffuse large B-cell lymphoma (DLBCL), CD5 positivity was observed in 8% (121/1534) of cases. Immunohistochemical staining for cyclin D1 performed for these cases revealed one cyclin D1-positive and IGH/CCND1 fusion-positive case (0.9%, 1/114), namely pleomorphic variant MCL. Of the remaining 1413 patients initially diagnosed with CD5^- DLBCL, the diagnoses of two patients (0.1%) were amended to CD5^- blastoid variant MCL in the relapse phase based on morphology, cyclin D1 immunostaining, and fluorescence in situ hybridization. The incidence of CD5 negativity was similar between classical MCL and two aggressive variants. Accurate diagnosis of MCL variants was enabled by identifying a classical MCL component and/or CD5 positivity; however, we misdiagnosed two cases of CD5^- blastoid variant MCL. A small number of MCL variants may be included in CD5^- DLBCL cases. The diagnosis of CD5^- aggressive variant MCL remains challenging but crucial because of its therapeutic significance.

Mantle cell lymphomas with concomitant MYC and CCND1 breakpoints are recurrently TdT positive and frequently show high-grade pathological and genetic features

Chromosomal breakpoints involving the MYC gene locus, frequently referred to as MYC rearrangements (MYC - R+), are a diagnostic hallmark of Burkitt lymphoma and recurrent in many other subtypes of B-cell lymphomas including follicular lymphoma, diffuse large B-cell lymphoma and other high-grade B-cell lymphomas and are associated with an aggressive clinical course. In remarkable contrast, in MCL, only few MYC - R+ cases have yet been described. In the current study, we have retrospectively analysed 16 samples (MYC - R+, n = 15, MYC - R-, n = 1) from 13 patients and describe their morphological, immunophenotypic and (molecular) genetic features and clonal evolution patterns. Thirteen out of fifteen MYC - R+ samples showed a non-classical cytology including pleomorphic (centroblastic, immunoblastic), anaplastic or blastoid. MYC translocation partners were IG-loci in 4/11 and non-IG loci in 7/11 analysed cases. The involved IG-loci included IGH in 3 cases and IGL in one case. PAX5 was the non-IG partner in 2/7 patients. The MYC - R+ MCL reported herein frequently displayed characteristics associated with an aggressive clinical course including high genomic-complexity (6/7 samples), frequent deletions involving the CDKN2A locus (7/10 samples), high Ki-67 proliferation index (12/13 samples) and frequent P53 expression (13/13 samples). Of note, in 4/14 samples, SOX11 was not or only focally expressed and 3/13 samples showed focal or diffuse TdT-positivity presenting a diagnostic challenge as these features could point to a differential diagnosis of diffuse large B-cell lymphoma and/or lymphoblastic lymphoma/leukaemia.

PD-L1 expression is associated with ALK positivity and STAT3 activation, but not outcome in patients with systemic anaplastic large cell lymphoma

The programmed cell death 1 (PD-1) pathway is a recently recognized mechanism of tumor immune evasion. In this study, programmed cell death ligand 1 (PD-L1) expression was evaluated in 95 patients with systemic anaplastic large cell lymphoma: 45 ALK+ and 50 ALK-. ALK+ anaplastic large cell lymphoma was more often positive for PD-L1 than ALK- anaplastic large cell lymphoma (76% vs 42%, p = 0.002). ALK- anaplastic large cell lymphoma showed a strong correlation between PD-L1 expression and STAT3 activation (measured by pSTAT3^Tyr705) (r = 0.8, p < 0.0001). In contrast, the PD-L1/pSTAT3 correlation was weaker in ALK+ anaplastic large cell lymphoma (r = 0.4, p = 0.08). In ALK- anaplastic large cell lymphoma, the PD-L1+ subgroup was more often EMA positive (69% vs 20%, p = 0.02) and tended to be less often CD2+ (50% vs 83%, p = 0.059). In ALK+ anaplastic large cell lymphoma, PD-L1 was not associated with pathologic features (all p > 0.05). Negative ALK status and high IPI score (≥3) were associated with shorter overall survival (p = 0.009 and p = 0.0005, respectively). Overall survival was not different between patients with PD-L1+ vs PD-L1- anaplastic large cell lymphoma (p = 0.44), regardless of ALK status and International Prognostic Index (IPI) score. We conclude that PD-L1 expression is more common in ALK+ anaplastic large cell lymphoma than ALK- anaplastic large cell lymphoma. In ALK- anaplastic large cell lymphoma, PD-L1 is strongly correlated with STAT3 activation and is associated with more frequent EMA and less frequent CD2 expression. PD-L1 has no prognostic significance in predicting the outcome of patients with systemic anaplastic large cell lymphoma, regardless of ALK status. PD-L1 expression on the anaplastic large cell lymphoma cells suggests these patients as potential candidates for PD-1 blockade immunotherapy.

SOX11-negative Mantle Cell Lymphoma: Clinicopathologic and Prognostic Features of 75 Patients

Studies have suggested that SOX11 expression has prognostic implications in patients with mantle cell lymphoma (MCL), but the data are controversial. In this study, we describe the clinicopathologic and prognostic features of 75 patients with SOX11-negative MCL. Compared with patients with SOX11-positive MCL, SOX11-negative MCL patients more frequently had leukemic non-nodal disease (21% vs. 4%, P=0.0001). SOX11-negative MCLs more often showed classic morphology (83% vs. 65%, P=0.005), were more often positive for CD23 (39% vs. 22%, P=0.02) and CD200 (60% vs. 9%, P=0.0001), and had a lower proliferation index (Ki67 23% vs. 33%, P=0.04). Overall survival (OS) was not significantly different between patients with SOX11-negative versus SOX11-positive MCL (P=0.63). High Ki67 index and blastoid/pleomorphic morphology were associated with shorter OS in both SOX11-negative (P<0.05) and SOX11-positive MCL groups (P<0.05). A high Mantle Cell Lymphoma International Prognostic Index (MIPI) predicted poorer prognosis in patients with SOX11-negative MCL (P<0.0001), but not SOX11-positive MCL (P=0.09). Nodal involvement and stage III/IV disease were associated with poorer outcome in patients with SOX11-positive MCL (P=0.03 and 0.04, respectively), but not SOX11-negative MCL (P=0.88 and 0.74, respectively). In summary, SOX11-negative MCL is characterized by more frequent leukemic non-nodal disease, classic morphology, more frequent expression of CD23 and CD200, and a lower Ki67 index. Prognostic factors in patients with SOX11-negative MCL include morphology, Ki67 index, and MIPI score.

CD8 expression in anaplastic large cell lymphoma correlates with noncommon morphologic variants and T-cell antigen expression suggesting biological differences with CD8-negative anaplastic large cell lymphoma

Anaplastic large cell lymphoma (ALCL) is a T-cell neoplasm characterized by uniformly strong CD30 expression and common absence of T-cell markers. Most ALCL cases express CD4, but a small subset of ALCL cases has been reported to express CD8. Little is known about the clinicopathologic and prognostic features of CD8+ ALCL. In this study, CD8 was assessed in 158 patients with systemic ALCL: CD8 was positive in 13 of 67 (19%) ALK+ and 13 of 91 (14%) ALK-negative neoplasms. In ALK+ ALCL, the CD8+ subgroup more often showed a noncommon morphologic pattern (69% vs 13%, P = .0001) and was more often positive for CD2 (100% vs 45%, P = .001), CD3 (92% vs 24%, P = .0001), and CD7 (100% vs. 39%, P = .002), but less frequently positive for CD25 (50% vs. 100%, P = .02). Patients with ALK+ ALCL and CD8+ neoplasms also had a higher relapse rate (82% vs 48%, P = .05) and more often underwent stem cell transplant (73% vs 36%, P = .04). CD8 expression did not correlate with patient overall survival or progression-free survival regardless of ALK status (all P > 0.05). We conclude that CD8+ ALCL cases appear to be biologically different from the more common CD8-negative ALCL cases. Our data suggest that CD8 positivity in ALK+ ALCL helps to identify a subset of patients more prone to relapse or more in need of stem cell transplant during their clinical course, although there was no impact on survival in this cohort.

Three Synchronous Primary Extranodal Mantle Cell Lymphomas Involving Torus Tubarius, Posterior Nasopharynx, and Base of the Tongue 65 Years After Treatment of Chronic Sinusitis with Nasopharyngeal Radium Irradiation

Patient: Male, 81

Final Diagnosis: Mantle cell lymphoma

Symptoms: Dificulty in swallowing and pain in the right ear

Medication: —

Clinical Procedure: Otorhinolaryngology panendoscopy • biopsy of the tumors

Specialty: Otolaryngology

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

Mantle cell lymphoma (MCL) is usually CD23 negative, a feature helpful in distinguishing MCL from chronic lymphocytic leukemia/small lymphocytic lymphoma. However, a subset of MCL cases can be CD23+. Limited data are available regarding the clinicopathological features and prognosis of patients with CD23+ MCL. In this study, we reviewed 798 cases of MCL and identified 103 (13%) that were CD23+ by flow cytometry, all of which were positive for cyclin D1 and/or associated with CCND1/IGH. In all cases of CD23+ MCL, CD23 expression was dim partial or dim, unlike moderate to bright CD23 expression observed in chronic lymphocytic leukemia/small lymphocytic lymphoma. The clinicopathological features and outcome of patients with CD23+ MCL were compared with 240 patients with typical MCL negative for CD23. Patients with CD23+ MCL more often had an elevated leukocyte count (33% versus 18%, P = .009), bone marrow involvement (89% versus 78%, P = .02), stage 4 disease (87% versus 77%, P = .03), and a leukemic presentation (42% versus 11%, P = .0001). CD23+ MCL was also more often positive for CD200 (17% versus. 4.6%, P = .0005) and less commonly positive for SOX11 (55% versus. 74%, P = .027). All other clinicopathological features were similar. With similar treatment regimens and observation times, patients with CD23+ MCL had a significant better overall survival (P = .02) and progression-free survival (P = .029). In conclusion, CD23 expression was observed in 13% of MCL cases and is associated with a better prognosis in patients with MCL. CD23 is associated with leukocytosis, a leukemic presentation, bone marrow involvement, CD200 expression, and a lower frequency of SOX11 positivity.