CD200 is a useful diagnostic marker for identifying atypical chronic lymphocytic leukemia by flow cytometry

B-cell prolymphocytic leukemia: an enduring bona fide entity

B-cell prolymphocytic leukemia (B-PLL) was recognized as a distinct entity in the fourth edition of the World Health Organization (WHO) classification for hematolymphoid neoplasms (WHO-HAEM4); however, its de novo presentation has been removed from the upcoming 5th edition classification (WHO-HAEM5). We present a case of a 65-year-old man with leukocytosis, fatigue, and no organomegaly by imaging. Bone marrow examination showed a prolymphocytoid population comprising 78% of the marrow elements. After thorough exclusion of other entities by clinical parameters and ancillary methods, we concluded that this case represents a de novo case of B-PLL.

What Does Atypical Chronic Lymphocytic Leukemia Really Mean? A Retrospective Morphological and Immunophenotypic Study

Atypical chronic lymphocytic leukemia (CLL) is still defined according to morphological criteria. However, deviance from the typical surface immunological profile suggests an atypical immunological-based CLL. A large cohort of patients with CLL was retrospectively evaluated aiming at assessing morphological (FAB criteria), immunophenotypical (two or more discordances from the typical profile), and clinical-biological features of atypical CLL. Compared to typical cases, morphologically atypical CLL showed a greater percentage of unmutated IgVH and CD38 positivity, and a higher expression of CD20. Immunophenotypically atypical CLL was characterized by more advanced clinical stages, higher expression of CD20, higher rate of FMC7, CD79b and CD49d positivity, and by an intermediate-high expression of membrane surface immunoglobulin, compared to typical cases. When patients were categorized based on immunophenotypic and morphologic concordance or discordance, no difference emerged. Finally, morphological features better discriminated patients' prognosis in terms of time-to-first treatment, while concordant atypical cases showed overall a worse prognosis. Discordant cases by immunophenotype and/or morphology did not identify specific prognostic groups. Whether-in the era of molecular markers used as prognostic indicators-it does make sense to focus on morphology and immunophenotype features in CLL is still matter of debate needing further research.

Atypical Chronic Lymphocytic Leukemia-The Current Status

A diagnosis of typical chronic lymphocytic leukemia (CLL) requires the presence of ≥5000 clonal B-lymphocytes/μL, the coexistence of CD19, CD20, CD5, and CD23, the restriction of light chain immunoglobulin, and the lack of expression of antigens CD22 and CD79b. Atypical CLL (aCLL) can be distinguished from typical CLL morphologically and immunophenotypically. Morphologically atypical CLL cells have been defined mainly as large, atypical forms, prolymphocytes, or cleaved cells. However, current aCLL diagnostics rely more on immunophenotypic characteristics rather than atypical morphology. Immunophenotypically, atypical CLL differs from classic CLL in the lack of expression of one or fewer surface antigens, most commonly CD5 and CD23, and the patient does not meet the criteria for a diagnosis of any other B-cell lymphoid malignancy. Morphologically atypical CLL has more aggressive clinical behavior and worse prognosis than classic CLL. Patients with aCLL are more likely to display markers associated with poor prognosis, including trisomy 12, unmutated IGVH, and CD38 expression, compared with classic CLL. However, no standard or commonly accepted criteria exist for differentiating aCLL from classic CLL and the clinical significance of aCLL is still under debate. This review summarizes the current state of knowledge on the morphological, immunophenotypic, and genetic abnormalities of aCLL.

Methodological and conceptual challenges to the flow cytometric classification of leukemic lymphoproliferative disorders

The diagnosis of leukemic B-cell lymphoproliferative disorders (B-LPDs) is made by integrating clinical, cytological, cytometric, cytogenetic, and molecular data. This leaves room for differences and inconsistencies between experts. In this study, we examine methodological and conceptual aspects of the flow cytometric classification of leukemic B-LPDs that could explain them. Among methodological aspects, we discuss (1) the different statistical tests used to select and evaluate markers, (2) how these markers are analyzed, (3) how scores are interpreted, (4) different degrees to which diagnostic information is used, and (5) and the impact of differences in study populations. Among conceptual aspects, we discuss (1) challenges to integrating different biological data points, (2) the under examination of the costs of misclassification (false positives and false negatives), and finally, (3) we delve into the impact of the lack of a true diagnostic gold standard and the indirect evidence suggesting poor reproducibility in the diagnosis of leukemic B-LPDs. We then outline current harmonization efforts and our personal approach. We conclude that numerous flow cytometry scores and diagnostic systems are now available; however, as long as the considerations discussed remain unaddressed, external reproducibility and interobserver agreement will not be achieved, and the field will not be able to move forward if a true gold standard is not found.

A Flow Cytometry Panel for Differential Diagnosis of Mantle Cell Lymphoma from Atypical B-Chronic Lymphocytic Leukaemia

Background

Differential diagnosis of chronic lymphoproliferative disorders (CLDs) has remained challenging due to the highly variable morphology features and immunophenotyping. Currently, the development of multiple-marker panel analyses by flow cytometry has opened a broad way for diagnosis of CLDs.

Methods

We analyzed the peripheral blood and bone marrow samples of 131 patients with B-cell CLDs (including 91 chronic lymphocytic leukemia (CLL), 15 atypical CLL, 14 mantle cell lymphoma (MCL), and 11 CD5-/CD10-lymphoma patients) from April 2018 to April 2019, using a panel of specific markers by flow cytometry.

Results

Our results indicated that the expression pattern of CD22, CD23, FMC-7, and CD5 allowed us to accurately and differentially diagnose the B-CLL, MCL, and CD5-/CD10- lymphoma, while it was not capable of differentiating MCL from atypical CLL. We, however, found that the expression patterns of CD38 and immunoglobulin light chain differed significantly between atypical B-CLL and MCL. CD38 and lambda light chain were remarkably expressed in MCL patients (92.8% and 85%, respectively) compared to the atypical CLL (1.1% and 0% respectively), with the p value less than 0.001 for both markers. In contrast to MCL patients, all the patients with atypical CLL, expressed kappa light chain. The immunohistochemistry method used for cyclin D1 confirmed that the flow cytometry detection of kappa and lambda light chains could provide a new approach with high sensitivity (91%) and moderate specificity (50%) to distinguish MCL patients from atypical B-CLL.

Conclusion

Expression of CD5, CD20 (bright), CD22, FMC-7, CD38, and lambda light chain with no expression of CD23 can accurately detect MCL and differentiate it from atypical B-CLL

[Study of cytogenetics and molecular biology in typical and atypical immunophenotypic chronic lymphocytic leukemia]

Objective: To analyze the differences in immunophenotype, cytogenetics, and molecular biology between typical and atypical immunophenotype chronic lymphocytic leukemia (CLL) , and explore the correlation of cytogenetic anomalies with gene mutations. Methods: This study included 488 patients diagnosed in the First Affiliated Hospital of Nanjing Medical University between November 2014 and May 2021. Of these, 382 patients scored 4-5 points, which was typical CLL (tCLL) , and 106 scored 3 points, which was atypical CLL (aCLL) as per the Royal Marsden Hospital Immunomarker Integral System. Peripheral blood cells were collected for immunophenotype by multiparameter flow cytometry in 488 patients, fluorescence in situ hybridization (FISH) was employed to detect cytogenetic anomalies in 359 patients, and gene mutations were detected by next-generation sequencing (NGS) in 330 patients. Results: The positive rates of CD10, CD22, CD49d, CD81, and FMC7 were significantly higher in the aCLL compared with the tCLL group (P=0.020, P<0.001, P<0.001, P=0.027, and P<0.001, respectively) , while the positive rates of CD5, CD23, CD148, and CD200 were lower in the former compared to the latter (P<0.001, P=0.017, P=0.041, and P<0.001, respectively) . aCLL exhibited a higher frequency of trisomy 12 and lower frequency of del (13q14) compared to the tCLL group (P<0.001 and P<0.001, respectively) . Moreover, aCLL patients also showed a higher incidence of NOTCH1 mutations than the tCLL patients (P=0.038) , while no statistically significant differences in other gene mutations occurred between the two groups. No significant differences in overall survival (OS) and treatment-free survival (TFS) occurred between aCLL and tCLL using Kaplan-Meier analysis (P>0.05) . Conclusion: aCLL has characteristic immunophenotype, cytogenetic, and somatic mutation that differ from tCLL, and this can provide reliable information for the diagnosis and differential diagnosis between the two groups.

A novel differential diagnosis algorithm for chronic lymphocytic leukemia using immunophenotyping with flow cytometry

INTRODUCTION

The availability of a clinical decision algorithm for diagnosis of chronic lymphocytic leukemia (CLL) may greatly contribute to the diagnosis of CLL, particularly in cases with ambiguous immunophenotypes. Herein we propose a novel differential diagnosis algorithm for the CLL diagnosis using immunophenotyping with flow cytometry.

METHODS

The hierarchical logistic regression model (Backward LR) was used to build a predictive algorithm for the diagnosis of CLL, differentiated from other lymphoproliferative disorders (LPDs).

RESULTS

A total of 302 patients, of whom 220 (72.8%) had CLL and 82 (27.2%), B-cell lymphoproliferative disorders other than CLL, were included in the study. The Backward LR model comprised the variables CD5, CD43, CD81, ROR1, CD23, CD79b, FMC7, sIg and CD200 in the model development process. The weak expression of CD81 and increased intensity of expression in markers CD5, CD23 and CD200 increased the probability of CLL diagnosis, (p < 0.05). The odd ratio for CD5, C23, CD200 and CD81 was 1.088 (1.050 - 1.126), 1.044 (1.012 - 1.077), 1.039 (1.007 - 1.072) and 0.946 (0.921 - 0.970) [95% C.I.], respectively. Our model provided a novel diagnostic algorithm with 95.27% of sensitivity and 91.46% of specificity. The model prediction for 97.3% (214) of 220 patients diagnosed with CLL, was CLL and for 91.5% (75) of 82 patients diagnosed with an LPD other than CLL, was others. The cases were correctly classified as CLL and others with a 95.7% correctness rate.

CONCLUSIONS

Our model highlighting 4 markers (CD81, CD5, CD23 and CD200) provided high sensitivity and specificity in the CLL diagnosis and in distinguishing of CLL among other LPDs.

Independent diagnostic utility of CD20, CD200, CD43 and CD45 in chronic lymphocytic leukaemia

Immunophenotyping plays a major role and is essential for establishing the diagnosis of chronic lymphocytic leukemia (CLL). Though CLL has a characteristic phenotype, diagnosis may be challenging due to immunophenotypic overlap with other B cell non-Hodgkin's lymphomas (B-NHL). Markers like CD200, CD43, CD20 and CD45 were found valuable in CLL and we investigated their diagnostic efficiency and accuracy in 174 patients with leukemic B-NHL. On the integration of four markers by a scoring system, 96% (49/51) of CLL cases showed a score of 3 or 4 and 90% (36/40) of non-CLL cases had a score of 0 or 1. This scoring system for CLL diagnosis showed a sensitivity of 98.2% and 96% in the analytical cohort and validation cohort respectively, which was significantly higher than the classical Matutes score. Hence we strongly suggest considering the expression of CD200, CD20, CD43 and CD45 in the diagnosis of B-NHL cases.

The potential differential diagnosis value and clinical significance of CD35 expression in B-chronic lymphoproliferative disorders

Background

Flow cytometry for immunophenotyping is the main method for diagnosing chronic lymphocytic leukemia (CLL). Differential diagnosis between CLL and other B-chronic lymphoproliferative disorders (B-CLPDs) is sometimes difficult. This study aimed to investigate whether cluster of differentiation 35 (CD35) could be a useful marker for the differential diagnosis of CLL and other B-CLPDs.

Methods

The CD35 expression on lymphoma cells from 516 B-CLPD patients (347 CLL, 169 other B-CLPDs) was investigated through flow cytometry analysis. Serum C3 and C4 levels in B-CLPD patients were also evaluated.

Results

The results showed that the expression percentage and mean fluorescence intensity of CD35 were reduced in CLL cases compared with other B-CLPD patients. Furthermore, CD35 <17% produced a sensitivity of 81.8% and a specificity of 88.4% for supporting the diagnosis of CLL. Additionally, the addition of CD35 to Matutes score improved the score's discriminative power. The sensitivity of the Matutes score was improved from 81.3% to 88.5%, and the accuracy was improved from 96.6% to 97.6%. Finally, 15.0% and 16.4% of CLL patients had defective serum C3 and C4 levels at diagnosis, respectively.

Conclusions

Evaluating CD35 expression could have potential differential diagnostic value in distinguishing CLL from other B-CLPDs, especially between CLL and mantle cell lymphoma (MCL).

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.

A new score including CD43 and CD180: Increased diagnostic value for atypical chronic lymphocytic leukemia

Moreau score has been used to differentiate chronic lymphocytic leukemia (CLL) from other mature B‐cell neoplasms. However, it showed limitations in Asian patients. Therefore, we conducted a new score system replacing CD5 and CD23 with CD43 and CD180 to evaluate its diagnostic value of CLL. 237 untreated samples diagnosed with mature B‐cell neoplasms were collected and were randomly divided into an exploratory and a validation cohort by a 2:1 ratio. The expression of CD5, CD19, CD20, CD23, CD43, CD79b, CD180, CD200, FMC7, and surface immunoglobulin (SmIg) were analyzed among all the samples. A proposed score was developed based on the logistic regression model. The sensitivity and specificity of the proposed score were calculated by ROC curves. CD43/CD180, CD200, FMC7, and CD79b were included in our new CLL score, which showed a sensitivity of 91.8% and a specificity of 83.1%. These results were confirmed in a validation cohort with a sensitivity of 90.5% (p = 0.808) and a specificity of 79.5% (p = 0.639). In CD5 negative or CD23 negative CLL group, the new CLL score displayed improved sensitivity of 79.4% compared to Moreau score and CLLflow score (41.2% and 47.1%, respectively). In atypical CLL group, the new CLL score showed improved sensitivity of 84.2% compared to Moreau score and CLLflow score (61.4% and 64.9%, respectively). This proposed atypical CLL score helped to offer an accurate differentiation of CLL from non‐CLL together with morphological and molecular methods, particularly in Chinese patients with atypical immunophenotype.

The future of laboratory testing in chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) is a malignant lymphoproliferative disorder characterised by the accumulation of dysfunctional B-lymphocytes in the blood and lymphoid tissues. It is a clonally complex disease with a high degree of both intra-tumoural and inter-patient heterogeneity. This variability leads to a wide range of clinical outcomes and highlights the critical need for accurate prognostic tests in CLL. With the advent of a range of new targeted agents for CLL in recent years, there is also a clinical need for improved predictive tests to therapy. This review of laboratory testing in CLL focuses on emerging technologies for prognostication including single nucleotide polymorphism microarray for karyotypic analysis, targeted next generation sequencing analysis of the immunoglobulin heavy chain variable region gene as well as genes recurrently mutated in the disease such as TP53, and detection of minimal residual disease.

The contribution of CD200 to the diagnostic accuracy of Matutes score in the diagnosis of chronic lymphocytic leukemia in limited resources laboratories

Flow cytometry immunophenotyping has an essential role in distinguishing chronic lymphocytic leukemia from other B-chronic lymphoproliferative disorders. Recently, CD200 is considered as a relatively consistent marker in chronic lymphocytic leukemia. We retrospectively assessed CD200 expression in 252 patients with B chronic lymphoproliferative disorders with four-color flow cytometry. CD200 expression estimation included the proportion of positive cells (≥30%) and the mean fluorescence intensity ratio. Additionally, we have incorporated CD200 into Matutes score, also replaced FMC7 and CD79b in an attempt to improve the score discriminative power. Of 252 patients enrolled, 199(79%) patients were classified as chronic lymphocytic leukemia and 53 (21%) as other B-chronic lymphoproliferative disorders. All chronic lymphocytic leukemia cases and 20 of 53 (37.7%) of other B-chronic lymphoproliferative disorders demonstrated high CD200 expression (≥30%). Further, CD200 (≥30%) revealed a higher accuracy in comparison to other markers in Matutes score (range: 51%–92.5%). Also, CD200 addition to the Matutes score has correctly recognized all 199 chronic lymphocytic leukemia cases including 10 atypical chronic lymphocytic leukemia cases. As for non-CLL cases, 20 of 53 attained a higher score, yet keeping the original diagnosis. Moreover, CD200 enhanced the diagnostic accuracy of Matutes score to 100%, and when included in a simplified 4-markers score, showed an accuracy of 99.8% compared to 99.4% of Matutes score. In conclusion, CD200 is an accurate diagnostic marker for chronic lymphocytic leukemia, and can refine the modified Matutes score accuracy when added with other markers.

CD200 and Chronic Lymphocytic Leukemia: Biological and Clinical Relevance

CD200, a transmembrane type Ia glycoprotein belonging to the immunoglobulin protein superfamily, is broadly expressed on a wide variety of cell types, such as B lymphocytes, a subset of T lymphocytes, dendritic cells, endothelial and neuronal cells. It delivers immunosuppressive signals through its receptor CD200R, which is expressed on monocytes/myeloid cells and T lymphocytes. Moreover, interaction of CD200 with CD200R has also been reported to play a role in the regulation of tumor immunity. Overexpression of CD200 has been reported in chronic lymphocytic leukemia (CLL) and hairy cell leukemia but not in mantle cell lymphoma, thus helping to better discriminate between these different B cell malignancies with different prognosis. In this review, we focus on the role of CD200 expression in the differential diagnosis of mature B-cell neoplasms and on the prognostic significance of CD200 expression in CLL, where conflicting results have been published so far. Of interest, increasing evidences indicate that anti-CD200 treatment might be therapeutically beneficial for treating CD200-expressing malignancies, such as CLL.

Measurable residual disease in the treatment of chronic lymphocytic leukemia

Treatment outcomes of chronic lymphocytic leukemia (CLL) have improved since chemoimmunotherapy and novel drugs became available for CLL treatment; therefore, more sensitive methods to evaluate residual CLL cells in patients are required. Measurable residual disease (MRD) has been assessed in several clinical trials on CLL using flow cytometry, real-time quantitative PCR (RQ-PCR) with allele-specific oligonucleotide (ASO) primers, and high-throughput sequencing. MRD assessment is useful to predict the treatment outcomes in the context of chemotherapy and treatment with novel drugs such as venetoclax. In this review, we discuss major techniques for MRD assessment, data from relevant clinical trials, and the future of MRD assessment in CLL treatment.

CD markers variations in chronic lymphocytic leukemia: New insights into prognosis

Chronic lymphocytic leukemia (CLL) is one of the most commonly occurring adult leukemias that is associated with clonal accumulation of mature apoptosis-resistant B-cells in bone marrow, peripheral blood, and specific tissues. Different pathogenesis factors can contribute to the aggression of the clinical course in this disease. Cytogenetic abnormalities and surface biomarkers of neoplastic CLL cells can be effective in the outcome of CLL, and the examination of changing CD markers expressions in the progression of CLL can be related to the prognosis of this disease. Changing expression levels of CD markers on lymphocytes and other cells in CLL patients can play a role in the aggressive clinical outcomes such as organomegaly, immunodeficiency, and advanced disease stages through their interaction with CLL microenvironment. Given the involvement of CD markers in the pathogenesis of CLL, it can be stated that recognizing the expression changes of CD markers in the cells involved in CLL can be a proper approach to evaluate prognosis among these patients.