CD200 expression in plasma cell myeloma

CD200 expression in hematopoietic neoplasms: Beyond a marker for diagnosis of B-cell neoplasms

CD200 (OX-2) is expressed in myeloid cells, B cells, subsets of T cells and on other normal and neoplastic non-hematopoietic cells. It interacts with CD200R and has a suppressive effect on T cells immune mediated response. We aimed to review CD200 expression and its role in the immune evasion of non-B cell hematopoietic neoplasms. In acute myeloid leukemia, CD200 seems to be related to the worst outcome, even in diseases of good prognosis, possibly due to an immunosuppressive effect. In plasma cell myeloma studies, while some have associated CD200 expression with worst prognosis possibly due to its suppressive effect on monocyte and T cell-mediated immune response, in others CD200 appeared to be a marker of a better outcome, or even showed no impact in event-free survival (EFS). Few studies have evaluated CD200 expression in T cell neoplasms; however, it appears to be a good immunophenotypic marker for angioimmunoblastic T cell lymphoma. In conclusion, CD200 appears to be involved in the immune evasion of malignant cells, which could affect the survival of these patients.

Clinical significance of CD200 expression in newly diagnosed multiple myeloma patients and dynamic changing during treatment

The aim of our study was to determine the impact of CD200 expression in newly diagnosed myltiple myeloma (MM) patients. CD200⁺ patients had significantly shorter median overall survival time (OS) than CD200^- patients (41.0 months vs. not reached, p = .009). The ratio of CD4⁺ to CD8⁺ T cells was lower in CD200⁺ patients and this reduction was significantly related to the increase of CD8⁺ T cells (p = .021). Moreover, we analyzed dynamic changes of CD200 expression in 47 CD200⁺ patients during treatment. Thirty-eight (80.9%) patients switched to CD200^- during treatment. Those patients had a favorable survival compared with the others (median OS, 65.0 vs. 32.0 months, p < .001; median PFS, 29.0 vs. 11.5 months, p = .027). We concluded that CD200 expression is an independent marker for MM prognostic estimation during treatment.

Increased CD200 expression in post-transplant lymphoproliferative disorders correlates with an increased frequency of FoxP3(+) regulatory T cells

CD200 is a membrane protein with immunosuppressive function and is expressed in many hematopoietic neoplasms, including acute myeloid leukemia (AML), plasma cell myeloma (PCM), and B-cell lymphoproliferative disorders, but is mostly negative in diffuse large cell lymphoma (DLBCL). CD200 has been shown to be a poor prognostic marker in AML and PCM; in AML, its immunomodulatory effect was linked to its ability to induce FoxP3(+) regulatory T cells (Tregs). Post-transplant lymphoproliferative disorders (PTLDs) arise in the setting of immune dysregulation, and tumor-infiltrating T cells, including Tregs, have been shown to correlate with outcome in these disorders. Because there is no literature data and CD200 is a potentially useful diagnostic and prognostic marker, we studied the expression of CD200 in a series of 38 PTLDs by immunohistochemistry (ICH), and found that 23.7% PTLDs were CD200(+) and showed strong membrane and cytoplasmic positivity in the neoplastic cells. All CD200(+) monomorphic PTLDs were DLBCLs and the median FoxP3(+) Treg count/hpf was higher in CD200(+) than in CD200(-) PTLDs: 22.6 vs. 0.30 (p < 0.001). These results indicated that almost a quarter of PTLDs in our series are CD200(+) by IHC, and CD200 expression correlates with the frequency of immunosuppressive Tregs. This is novel data and supports a pathophysiologic link between CD200 activity and Tregs. In our series, the 5-year overall survival was shorter in CD200(+) PTLDs, compared to CD200(-) patients, although this difference did not reach statistical significance. In addition, we find a higher proportion of CD200(+) monomorphic PTLD-DLBCLs (31.0%), as compared to de novo DLBCLs (7-8%, as found here and in other studies). This may indicate differential expression of CD200 in B-cell lymphomas arising in the setting of immune dysregulation, and raises the possibility of anti-CD200 immunotherapy for these cases.

Revving the CAR - Combination strategies to enhance CAR T cell effectiveness

Chimeric antigen receptor (CAR) T cell therapy is currently approved for treatment of refractory B-cell malignancies. Response rates in these diseases are impressive by historical standards, but most patients do not have a durable response and there remains room for improvement. To date, CAR T cell activity has been even more limited in solid malignancies. These limitations are thought to be due to several pathways of resistance to CAR T cells, including cell-intrinsic mechanisms and the immunosuppressive tumor microenvironment. In this review, we discuss current experimental strategies that combine small molecules and monoclonal antibodies with CAR T cells to overcome these resistance mechanisms. We describe the biological rationale, pre-clinical data and clinical trials in progress that test the efficacy and safety of these combinations.

Flow Cytometric Evaluation of Traditional and Novel Surface Markers for the Diagnosis of Plasma Cell Dyscrasias

Increasing interest has been expressed for flow cytometric immunophenotyping for diagnosis and monitoring in plasma cell dyscrasias over the last decades. The aim of this investigation was to compare the expression strength of various cell surface markers used traditionally or currently under investigation on normal and abnormal PC populations. We enrolled 295 consecutive patients undergoing bone marrow aspiration in the workup of monoclonal gammopathies, selecting 54 normal and 241 abnormal PC populations via flow cytometry to characterize the expression of CD45, CD38, CD138, CD19, CD56, CD20, CD27, CD28, CD81, CD117 and CD200 on the cell surface of PCs. We observed significant differences in the expression strength of all assessed markers between normal and abnormal PC populations in all markers except for CD20. While none of them was conclusive on its own, the combination of CD81 positivity and CD117 negativity was present in 98.1% of normal PC populations tested. In contrast, particularly CD117 positivity, but also CD81 negativity was indicative of an abnormal PC phenotype. Our results highlight the descriptive value of CD81 and CD117 for the allocation of bone marrow PCs to a normal or abnormal phenotype.

Single nucleotide polymorphism rs3746444 in miR‑499a affects susceptibility to non‑small cell lung carcinoma by regulating the expression of CD200

The present study evaluated the association between single nucleotide polymorphism (SNP) rs3746444 and the risk of non‑small cell lung carcinoma (NSCLC) in a Chinese population. Computational analyses and luciferase assays were performed to investigate the regulatory relationship between miR‑499a and CD200. In addition, reverse transcription‑quantitative polymerase chain reaction and western blot assays were performed to examine the effect of rs3746444 on the expression of miR‑499a and CD200. The results demonstrated a significant difference in the smoking history of patients carrying malignant pulmonary nodules and those carrying benign pulmonary nodules. Furthermore, CD200 was demonstrated to be a direct target of miR‑499a, and a miR‑499a binding site was located in the 3'UTR of CD200. Notably, the levels of miR‑499a in malignant pulmonary nodules were higher compared with benign pulmonary nodules, while the levels of CD200 were higher in benign pulmonary nodules compared with malignant pulmonary nodules. In addition, the subjects carrying the AA genotype of SNP rs3746444 exhibited upregulated miR‑499a expression and reduced CD200 expression, compared with the subjects carrying AG and GG genotypes. These findings indicate that the SNP rs3746444 in miR‑499a could affect the prognosis of NSCLC patients by regulating the expression of CD200.

Current applications of multiparameter flow cytometry in plasma cell disorders

Multiparameter flow cytometry (MFC) has become standard in the management of patients with plasma cell (PC) dyscrasias, and could be considered mandatory in specific areas of routine clinical practice. It plays a significant role during the differential diagnostic work-up because of its fast and conclusive readout of PC clonality, and simultaneously provides prognostic information in most monoclonal gammopathies. Recent advances in the treatment and outcomes of multiple myeloma led to the implementation of new response criteria, including minimal residual disease (MRD) status as one of the most relevant clinical endpoints with the potential to act as surrogate for survival. Recent technical progress led to the development of next-generation flow (NGF) cytometry that represents a validated, highly sensitive, cost-effective and widely available technique for standardized MRD evaluation, which also could be used for the detection of circulating tumor cells. Here we review current applications of MFC and NGF in most PC disorders including the less frequent solitary plasmocytoma, light-chain amyloidosis or Waldenström macroglobulinemia.

High CD200 expression is associated with poor prognosis in cytogenetically normal acute myeloid leukemia, even in FlT3-ITD-/NPM1+ patients

Overexpression of CD200, a trans-membrane protein belonging to the immunoglobulin superfamily, has been associated with poor prognosis in patients with acute myeloid leukemia (AML). As few data are available in the subset of cytogenetically-normal (CN) AML, we retrospectively evaluated the correlations between CD200 expression and response to therapy in a series of 139 adults with CN-AML. CD200 was expressed in 67/139 (48%) cases; 18 of them (28%) expressed CD200 at high intensity. No differences in CD200 expression rate were observed according to age, WBC count, type of leukemia, FLT3 or NMP1 mutation, and CD56 expression. A higher incidence of CD200 expression was observed in CD34+ cases (P<0.0001) and in BCL2+ patients (P=0.04). Complete remission (CR) was evaluable achieved in 98 patients (70%): 56/71 (79%) in CD200- and 47/67 (63%) in CD200+ patients (P=0.03), with a lower CR rate in patients with high CD200 intensity (9/18, 50%). CD200 expression had a negative impact on long-term outcome. CD200 expression, per se, did not impact on disease-free survival (DFS), but cases with high CD200 expression had a lower 3-year DFS compared to CD200-negative and low-expressing ones (0% vs 65% vs 68%, P=0.019). Three-year overall survival (OS) was 51% in CD200- and 27% in CD200+ patients (P=0.01), with a significant difference among cases with low or high CD200 expression (35% vs 0%, P=0.001). CD200 high expression defined a group with very poor DFS and OS also among the 37 FLT3-/NPM1+: 3-year DFS and OS were 88% and 60% in CD200-, 50% and 32% in CD200 low and 0% and 0% in CD200 high patients, respectively (P=0.01 for DFS and P=0.05 for OS). Our data suggest a negative impact of CD200 expression in CN-AML, with a further worsening in high-expressing cases, also in the subset of FLT3-/NPM1+ patients.

Role of Flow Cytometry in the Diagnosis and Prognosis of Plasma Cell Myeloma

This article provides an overview of the role of flow cytometry in the diagnosis and follow-up of plasma cell myeloma. A brief introduction to the general immunophenotypic features of normal and myeloma plasma cells is provided, followed by a discussion of technical issues as they relate to the application of flow cytometry in this entity. The prognostic and therapeutic utility of flow cytometric immunophenotyping in myeloma is also analyzed, with an emphasis on the growing role of minimal residual analysis as potential biomarker for evaluating treatment efficacy and for tailoring risk-adapted treatment, in prospective clinical trials.

CD200 Expression on Plasma Cell Myeloma Cells is Associated with the Efficacies of Bortezomib, Lenalidomide and Thalidomide

Plasma cell myeloma (PCM) is a devastating disease with a highly heterogeneous outcome, with survival ranging from a few months to longer than 10 years. Treatment of multiple myeloma has changed markedly in the past decade due to the development of new drugs such as bortezomib, lenalidomide and thalidomide, which have greatly improved the outcome of PCM. The clinical and prognostic value of immunophenotyping in PCM remains questionable. The aim of this study was to determine the diagnostic and prognostic significance of CD200 expression in newly diagnosed PCM. We retrospectively reviewed the records of 107 patients newly diagnosed with PCM at Showa University Hospital between January 2004 and September 2013. Expression of CD200 was studied by immunohistochemistry. Clinical and pathological parameters were compared between CD200-positive and CD200-negative cases. CD200-positive PCM cases had lower serum albumin (p = 0.0001) compared to those without CD200 expression. Our results showed no significant difference in median overall survival between patients with CD200-positive and CD200-negative PCM. However, there was a strong correlation between CD200 expression and serum albumin level. In the CD200-negative group, median overall survival was significantly longer in patients who received new drug treatment. These findings suggest that CD200 expression is a useful marker for evaluation of the severity of PCM and that lack of CD200 expression may improve the sensitivity of PCM to therapy with new drugs.

Flow cytometric analysis of CD200 expression by pulmonary small cell carcinoma

BACKGROUND

CD200 is a membrane bound glycoprotein that is expressed by a variety of normal tissues and hematopoietic malignancies. Flow cytometric analysis of CD200 expression has utility in the evaluation of mature B-cell neoplasms, myeloma, and acute leukemia; however, CD200 expression in nonhematopoietic malignancies has not been extensively studied.

METHODS

We studied 14 cases of biopsy proven pulmonary small cell carcinoma in which a discrete CD45 negative, CD56 positive abnormal cell population was identified by flow cytometry. We retrospectively evaluated these cases for flow cytometric and immunohistochemical evidence of CD200 expression.

RESULTS

Twelve of the 14 cases of pulmonary small cell carcinoma showed convincing expression of CD200 by both immunohistochemistry and flow cytometry.

CONCLUSIONS

Pulmonary small cell carcinoma frequently expresses CD200 at a level that can be detected by flow cytometry and immunohistochemistry. CD200 expression therefore may be used to help identify pulmonary small cell carcinoma in flow cytometry specimens and tissue sections. CD200 may also play a role in the biology of pulmonary small cell carcinoma and is a potential target of future therapies. © 2015 International Clinical Cytometry Society.

Differential expression of CD200 in B-cell neoplasms by flow cytometry can assist in diagnosis, subclassification, and bone marrow staging

OBJECTIVES

To analyze CD200 expression by flow cytometry in a large series of B-cell neoplasms in a variety of tissue types in comparison with benign B-lineage cells.

METHODS

We measured CD200 expression levels in 505 peripheral blood (PB), bone marrow (BM), and lymphoid tissue biopsy specimens, including 364 cases positive for B-cell leukemias and lymphomas.

RESULTS

CD200 expression in chronic lymphocytic leukemia cases was as bright as or brighter than normal PB B cells in nearly all cases, while mantle cell lymphoma (MCL) cases were usually dim or negative. However, rare MCL cases (about 5%) were moderately bright for CD200. Marginal zone lymphomas varied by subtype, with nodal cases brighter, splenic cases dimmer, and extranodal cases heterogeneous for CD200 expression. Follicular lymphoma (FL) cells were brighter for CD200 in BM specimens than in lymph nodes. In some BM specimens, dim CD200 could distinguish FL cells from background hematogones. Large B-cell lymphomas of the non-germinal center type tended to be brighter for CD200 than those of the germinal center type, while Burkitt lymphomas were negative.

CONCLUSIONS

CD200 staining by flow cytometry can be useful in the differential diagnosis of B-cell neoplasms and in their detection in the BM.

Diagnostic and prognostic significance of CD200 expression and its stability in plasma cell myeloma

Aim

Previous studies showed that CD200 expression is a prognostic factor for plasma cell myeloma (PCM), but the prognostic effect is conflicting between studies. We studied CD200 protein expression and the stability of expression in PCM to clarify its potential utility in diagnosis, prognosis and monitoring of disease.

Method

CD200 expression was studied in 77 cases of PCM by immunohistochemistry on paraffin sections from decalcified bone marrow biopsies.

Result

There were 16 newly diagnosed cases and 61 post-treatment cases from 54 patients: 37 men and 17 women, with a median age of 62 years (range, 41–88 years). CD200 demonstrated moderate to strong membrane expression in positive cases. Fifty-six of 77 cases (73%) showed CD200 expression. Twenty of the 22 (91%) patients with serial specimens demonstrated stable CD200 expression (n=15) or lack of CD200 expression (n=5). One patient lost CD200 expression, while another one gained CD200 expression during treatment. The clinical, pathologic and cytogenetic features between the CD200+ group and the CD200− group were similar in most instances. However, CD200 expression was associated with lower serum β2-microglobulin (p=0.03). There was no significant difference in overall survival and progression-free survival between the CD200+ and CD200− patients (p>0.05).

Conclusions

CD200 is expressed in a majority of PCM cases, and the expression is stable during the treatment process. Therefore, immunohistochemical expression of CD200 is a useful marker for the diagnosis and follow-up of PCM.

Immunological dysregulation in multiple myeloma microenvironment

Multiple Myeloma (MM) is a systemic hematologic disease due to uncontrolled proliferation of monoclonal plasma cells (PC) in bone marrow (BM). Emerging in other solid and liquid cancers, the host immune system and the microenvironment have a pivotal role for PC growth, proliferation, survival, migration, and resistance to drugs and are responsible for some clinical manifestations of MM. In MM, microenvironment is represented by the cellular component of a normal bone marrow together with extracellular matrix proteins, adhesion molecules, cytokines, and growth factors produced by both stromal cells and PC themselves. All these components are able to protect PC from cytotoxic effect of chemo- and radiotherapy. This review is focused on the role of immunome to sustain MM progression, the emerging role of myeloid derived suppressor cells, and their potential clinical implications as novel therapeutic target.

CD200 has an important role in the differential diagnosis of mature B-cell neoplasms by multiparameter flow cytometry

BACKGROUND

Multiparameter flow cytometry is a useful tool for the diagnostic evaluation of mature B-cell neoplasms (MBN). Recently, it has been shown that CD200 may improve the distinction between chronic lymphocytic leukemia (CLL; CD200+) and mantle cell lymphoma (MCL; CD200-), but the role of CD200 expression in atypical CLL and other MBN remains to be established.

METHODS

To address this issue, we investigated the expression of CD200 in 159 consecutive cases of MBN.

RESULTS

CD200 was strongly expressed in CLL and was revealed to be an excellent marker to distinguish CLL from MCL, even in cases of atypical CLL. However, lack of CD200 was not an exclusive finding of MCL, being also observed in other MBNs. Furthermore, CD200 was highly expressed in hairy cell leukemia, being useful in the differential diagnosis of lymphomas with villous lymphocytes. Herein, we propose an algorithm to classify CD5+ MBNs based on the expression of CD200, CD11c, heavy chain immunoglobulins, and Matutes score.

CONCLUSIONS

These results expand the understanding of the CD200 expression in MBNs, giving further support for the inclusion of this marker in the routine investigation by flow cytometry.

Residual malignant and normal plasma cells shortly after high dose melphalan and stem cell transplantation. Highlight of a putative therapeutic window in Multiple Myeloma?

Multiple Myeloma (MM) is an incurable malignant plasma cell disorder. We have evaluated the counts of Multiple Myeloma Cells (MMCs) and normal plasma cells (N-PCs), seven days after high-dose melphalan (HDM) and autologous stem transplantation (ASCT). Two third of patients had detectable minimal residual disease (MRD⁺) (71.7 MMCs/μL) after induction treatment with dexamethasone and proteasome inhibitor. MMC counts were reduced by 92% (P ≤ .05) but not eradicated 7 days after HDM+ASCT. Post-HDM+ASCT MMCs were viable and bathed in a burst of MMC growth factors, linked with post-HDM aplasia. In one third of patients (MRD⁻ patients), MMCs were not detectable after induction treatment and remained undetectable after HDM+ASCT. Major difference between MRD⁻ and MRD⁺ patients is that N-PC counts were increased 3 fold (P < .05) by HDM+ASCT in MRD⁻ patients, but were unaffected in MRD⁺ patients. Possible explanation could be that clearance of MMCs in MRD⁻ patients makes more niches available for N-PCs. Thus, MMCs are not fully eradicated shortly after HDM, are bathed in high concentrations of MMC growth factors in an almost desert BM, are viable in short-term culture, which suggests providing additional therapies shortly after HDM to kill resistant MMCs before full repair of lesions.

CD200 expression in plasma cells of nonmyeloma immunoproliferative disorders: clinicopathologic features and comparison with plasma cell myeloma

The majority of plasma cell myelomas (PCMs) are positive for CD200, a membrane protein with immunosuppressive function. There are no flow cytometry data in the literature on plasma cell CD200 expression in other immunoproliferative disorders. Therefore we used flow cytometry to study the expression of CD200 on plasma cells in diagnostic bone marrow aspirates from 61 patients with monoclonal gammopathy of undetermined significance (MGUS) and 10 patients with lymphoplasmacytic lymphoma (LPL). For comparison, we evaluated CD200 expression in 74 PCM bone marrow biopsies. Thirty-three (54.1%) of 61 MGUS cases and 2 (20.0%) of 10 LPL cases were CD200+. Comparative clinicopathologic parameters for MGUS cases, based on CD200 expression status, showed no differences between the 2 groups. The proportion of CD200+ PCMs (73.0%) in our series was significantly higher than that of CD200+ MGUS (P = .030) and CD200+ LPL (P = .002) cases.

Coinhibitory molecules in hematologic malignancies: targets for therapeutic intervention

The adaptive immune system can be a potent defense mechanism against cancer; however, it is often hampered by immune suppressive mechanisms in the tumor microenvironment. Coinhibitory molecules expressed by tumor cells, immune cells, and stromal cells in the tumor milieu can dominantly attenuate T-cell responses against cancer cells. Today, a variety of coinhibitory molecules, including cytotoxic T lymphocyte–associated antigen-4, programmed death-1, B and T lymphocyte attenuator, LAG3, T-cell immunoglobulin and mucin domain 3, and CD200 receptor, have been implicated in immune escape of cancer cells. Sustained signaling via these coinhibitory molecules results in functional exhaustion of T cells, during which the ability to proliferate, secrete cytokines, and mediate lysis of tumor cells is sequentially lost. In this review, we discuss the influence of coinhibitory pathways in suppressing autologous and allogeneic T cell–mediated immunity against hematologic malignancies. In addition, promising preclinical and clinical data of immunotherapeutic approaches interfering with negative cosignaling, either as monotherapy or in conjunction with vaccination strategies, are reviewed. Numerous studies indicate that coinhibitory signaling hampers the clinical benefit of current immunotherapies. Therefore, manipulation of coinhibitory networks is an attractive adjuvant immunotherapeutic intervention for hematologic cancers after standard treatment with chemotherapy and hematopoietic stem cell transplantation.

Diagnostic usefulness and prognostic impact of CD200 expression in lymphoid malignancies and plasma cell myeloma

The membrane glycoprotein MRC OX-2 (CD200) is expressed in several lymphoid malignancies. However, the diagnostic usefulness and potential prognostic importance of CD200 expression have not been rigorously examined. We show that CD200 is uniformly expressed in chronic lymphocytic leukemia (CLL) and absent in mantle cell lymphoma (MCL). It is important to note that expression of CD200 is retained even in CLLs with immunophenotypic aberrancies, making CD200 a particularly useful marker for discrimination between these cases and MCL. CD200 is expressed in nearly all precursor B-lymphoblastic leukemias, with aberrant overexpression or underexpression compared with normal B-cell progenitors in 55% of cases. More than 70% of plasma cell myelomas (PCMs) expressed CD200, and loss of CD200 expression in PCM may be associated with more clinically aggressive disease. CD200 is expressed in several hematolymphoid neoplasms. Analysis of its expression has several diagnostic and potentially prognostic applications in the flow cytometric evaluation of lymphoid malignancies.

Monoclonal antibody-based therapy as a new treatment strategy in multiple myeloma

The introduction of autologous stem cell transplantation combined with the introduction of immunomodulatory drugs (IMiDs) and proteasome inhibitors has significantly improved survival of multiple myeloma patients. However, ultimately the majority of patients will develop refractory disease, indicating the need for new treatment modalities. In preclinical and clinical studies, promising results have been obtained with several monoclonal antibodies (mAbs) targeting the myeloma tumor cell or the bone marrow microenvironment. The mechanisms underlying the therapeutic efficacy of these mAbs include direct induction of tumor cell apoptosis via inhibition or activation of target molecules, complement-dependent cytotoxicity and antibody-dependent cell-mediated cytotoxicity (ADCC). The capability of IMiDs to enhance ADCC and the modulation of various important signaling cascades in myeloma cells by both bortezomib and IMiDs forms the rationale to combine these novel agents with mAbs as new treatment strategies for myeloma patients. In this review, we will give an overview of various mAbs directly targeting myeloma tumor cells or indirectly via effects on the bone marrow microenvironment. Special focus will be on the combination of these mAbs with IMiDs or bortezomib.

Clinicopathologic analysis of the impact of CD23 expression in plasma cell myeloma with t(11;14)(q13;q32)

A recent study has shown that 10% of plasma cell myelomas (PCMs) express CD23 and that expression is associated with abnormalities of chromosome 11, mainly t(11;14)(q13;q32); however, only 40% of t(11;14)(+) PCMs express CD23. Because these results were generated in a limited patient cohort and because the clinical relevance of CD23 expression in PCMs with t(11;14)(q13;q32) has not been fully characterized, we addressed this question in a large series of patients with t(11;14)(+) PCM. Forty-two bone marrow biopsies from patients with t(11;14)(+) PCM were evaluated for CD23 expression by immunohistochemistry. CD23 expression was correlated with laboratory and clinical data and outcome after autologous stem cell transplantation, including event-free survival and overall survival (OS). Plasma cell myelomas with t(11;14)(q13;q32) were frequently CD20(+) (46.4%) and CD56(-) (53.8%) and had a nonhyperdiploid karyotype (97.6%) with frequent 13q deletion (33.3%). Of 42 cases, 19 (45.2%) expressed CD23. CD23(+) PCMs were more likely to present with platelet counts less than 150 × 10(3)/μL (100% vs 50%, P = .006). There were no significant differences in other laboratory or presenting clinical data. The median event-free survival in patients treated with autologous stem cell transplantation (n = 29) was similar regardless of CD23 status, whereas the median OS (all patients) was longer in CD23(-) than in CD23(+) PCMs: not reached vs 3365 days (P = .08). Our findings suggest that patients with t(11;14)(+)/CD23(+) PCM present with lower platelet counts and may have a shorter OS than those with t(11;14)(+)/CD23(-) PCM.