Typical and atypical chronic lymphocytic leukemia differ clinically and immunophenotypically

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.

[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.

Flow Cytometric Expression of CD49d in Newly Diagnosed Chronic Lymphocytic Leukemia and Its Correlation with Established Prognostic Markers

Introduction Chronic lymphocytic leukemia (CLL) is the commonest hematological malignancy in the West but is relatively uncommon in India. The prognosis of CLL is determined by well-established prognostic markers. CD49d has been emerging as a promising prognostic marker in CLL. CD49d expression in CLL has been found to have an aggressive clinical course, shorter time to first treatment, and poorer prognosis. The aim of this study was to analyze the flow cytometric expression of CD49d in newly diagnosed CLL and to correlate its expression with clinico-hematological parameters.

Materials and Methods Twenty-five consecutive patients of CLL, diagnosed on flow cytometry, were included in the study. Patients on treatment or those with relapse were excluded. The panel for flow cytometry included the routine markers used for CLL diagnosis along with CD49d. The expression of CD49d was correlated with clinico-hematological parameters in all patients. “R” software was used for the statistical analysis. Fisher's exact test and Wilcox test were used to assess the correlation of CD49d to categorical and continuous data, respectively.

Results The mean age of the patients was 62.6 ± 12.5 years, and 80% were symptomatic at diagnosis. CD49d expression was found in 44% cases, with a higher proportion being male patients. CD49d and prolymphocyte percentage showed a statistically significant correlation (p = 0.0007). We found a statistically significant correlation between CD49d expression and lymphadenopathy and splenomegaly with p-values of 0.033 and 0.0472, respectively. CD49d positivity correlated significantly with a higher Rai stage (p = 0.0196) and intermediate and high-risk cases according to Binet staging (p = 0.033).

Conclusion CD49d expression in the present study correlated with a higher prolymphocyte percentage, lymphadenopathy, splenomegaly, and higher Rai and Binet stages. CD49d expression on flow cytometry was reproducible and easy to interpret.

Concordance between flow cytometry CLL scores

INTRODUCTION

Multiple flow cytometry scores/diagnostic systems for the classification of leukemic lymphoproliferative disorders (LPD) have been published but few have been compared between them.

PATIENTS AND METHODS

We classified a cohort of leukemic LPD based on eleven published flow cytometry scores/diagnostic systems and compared their classification as chronic lymphocytic leukemia (CLL) or non-CLL LPD.

RESULTS

329 patients were included. Patients classified as CLL ranged from 46% to 73%, depending on the score/diagnostic system used. All eleven scores/diagnostic systems agreed in 184/324 (57%) of patients while in 58/324 (18%) at least two scores/diagnostic systems classified the patient differently (from the majority). Fleiss kappa was 0.74, but pairwise agreement was variable (Cohen's kappa: 0.48 to 0.87).

CONCLUSION

This study found a suboptimal agreement between published flow cytometry scores/diagnostic systems for the classification of LPD.

Management of atypical chronic lymphocytic leukemia presenting with extreme leukocytosis

Atypical chronic lymphocytic lymphoma (CLL) with CCND1 translocation is poorly described, particularly in the era of modern inhibitors of the B-cell receptor pathway. We present a patient with atypical CLL who had a significant response to ibrutinib, highlighting the effectiveness of this agent in higher risk CLL subgroups.

Chronic lymphocytic leukemia with TP53 gene alterations: a detailed clinicopathologic analysis

TP53 alteration in chronic lymphocytic leukemia indicates a high-risk disease that is usually refractory to chemotherapy. It may be caused by deletion of 17p involving the loss of TP53 gene, which occurs in low percentage of patients at diagnosis but can be acquired as the disease progresses. Since patients may harbor TP53 mutation without chromosome 17p deletion, consensus recommendations call for both cytogenetic and PCR mutation analysis of TP53 in chronic lymphocytic leukemia. We conducted a single-institution retrospective study to investigate the clinicopathologic features of chronic lymphocytic leukemia with TP53 alterations as well as the utility of different diagnostic modalities to identify p53 alterations. Forty percent of chronic lymphocytic leukemia patients with TP53 alterations demonstrated atypical lymphocytes with cleaved/irregularly shaped nuclei and/or large atypical lymphoid cells with abundant cytoplasm in the peripheral blood. Progression was also observed in lymph node and bone marrow samples (21% with Richter transformation; 33% with findings suggestive of "accelerated phase" of chronic lymphocytic leukemia including prominent proliferation centers and/or increased numbers of prolymphocytes). However, the presence of the morphologic features suggestive of "accelerated phase" had no effect on overall survival within the chronic lymphocytic leukemia group with TP53 abnormalities (p > 0.05). As previously reported by others, a subset of patients with TP53 alterations were only identified by either PCR mutation analysis (12%) or cytogenetic studies (14%). p53 immunostain positivity was only identified in approximately half of the patients with TP53 alterations identified by either method, and it failed to identify any additional patients with p53 abnormalities. In summary, chronic lymphocytic leukemia patients with TP53 alterations frequently show atypical morphologic features. Use of multiple modalities to identify p53 abnormalities is recommended to ensure optimal sensitivity and specificity.

Del17p does not always significantly influence the survival of B-cell chronic lymphoproliferative disorders

B-cell chronic lymphoproliferative disorders (B-CLPD) comprise several entities with indolent clinical manifestations but heterogeneous survival. Cytogenetic aberrations are now the standard prognostic predictors in chronic lymphocytic leukemia (CLL) but have been less investigated in other subtypes of B-CLPD. In this study, we detected cytogenetic aberrations by fluorescence in situ hybridization (FISH) in 875 B-CLPD patients, based on a panel probes locating at 13q14, 11q22, 17p13 and CEP12. We identified del17p acted as the independent adverse cytogenetic predictor for overall survival (OS) in CLL. Del13q, del11q and del17p were adverse factors for OS in Waldenström's macroglobulinemia in the univariate analysis but lost their role in the multivariate analysis. Trisomy 12 acted as an independent poor factor for both marginal zone lymphoma (MZL) and unclassified B-CLPD (BCLPD-U) subtype. Del17p did not impact survival in MZL and BCLPD-U patients. These contrasting results indicate different roles of the same cytogenetic aberrations in the pathogenesis of each B-CLPD subtype. As del17p contributed to the poorest survival in CLL and desired extraordinary treatment strategy, the imitation of CLL strategy to other B-CLPD with del17p should be carefully advocated based on this study.

Pathology of indolent B-cell neoplasms other than follicular lymphoma

Indolent B-cell lymphomas include follicular lymphoma (FL), chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and marginal zone lymphomas (MZLs). They are a diverse group of disorders with different clinical, morphological, immunophenotypic and genetic features. However, because of several histological similarities, such as in cell size and nodular structure, it may sometimes be difficult to differentiate them and to make a definitive diagnosis. In this review article, we summarize the histopathology of indolent B-cell neoplasms excluding FL and including hairy cell leukemia, and briefly mention recent genetic findings useful for their differential diagnosis. In addition, a provisional subtype of low-grade B-cell lymphoma, "prolymphocytic/paraimmunoblastic lymphoma", is described.

Chronic lymphocytic leukemia in Korean patients: frequent atypical immunophenotype and relatively aggressive clinical behavior

Chronic lymphocytic leukemia (CLL) is a mature B-cell neoplasm characterized by the expansion of CD5-positive lymphocytes in peripheral blood. While CLL is the most common type of leukemia in Western populations, the disease is rare in Asians. Hence, clinical and laboratory data and studies of CLL in Asian populations have been limited. In this study, we investigated the clinical and laboratory characteristics of CLL in Korea. A total of 39 patients who had been diagnosed with CLL during the period from January 2000 to October 2010 at a single institution in Korea were examined. Clinically, 67 % of the patients were classified as having advanced Binet stages B or C. Up to 56 % of the patients had an atypical immunophenotype with high frequencies of FMC7 positivity and strong CD22 positivity. Twenty-six patients (67 %) received chemotherapy, and more than half of the treated patients (54 %) expired. The overall survival rate at 5 years was estimated at 71 %, which was lower than previously reported. These findings suggested that CLL in Korea has atypical immunophenotypes and that its clinical behavior may be more aggressive than that in Western populations.

Nodal and leukemic small B-cell neoplasms

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

Diagnostic Workup of Small B Cell Lymphomas: A Laboratory Perspective

Small B cell lymphoma is a morphological designation to a group of B cell lymphomas which are composed of a clonal population of small lymphoid cells. The subtypes of this category have diagnostically distinct characteristics and different clinical behaviors and treatment. Correct diagnosis and classification of these subsets depend on the integration of morphologic, immunophenotypic, and molecular genetic features. In this paper, differential diagnosis of this category of tumors and a practical approach based on biomarker evaluation are discussed.

Pathologic and molecular genetic features of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is an indolent B-cell leukemia. While many patients may not require therapy, some patients will suffer a progressive course and die of their disease. This clinical heterogeneity is reflected in the molecular genetic heterogeneity that is becoming apparent through studies of immunoglobulin heavy chain gene mutational status, chromosomal numerical abnormalities, microRNA abnormalities, and genetic abnormalities identified by whole genome sequencing. Indeed, many of these studies are becoming routine in the assessment of patients with CLL or being incorporated into clinical trials to further stratify patients for appropriate therapies. Here, we will review the morphologic, immunophenotypic, and molecular genetic features of CLL and touch upon the concept of monoclonal B-cell lymphocytosis.

Relevance of IgVH gene somatic hypermutation and interphase cytogenetics in lymphomatous presentation of chronic lymphocytic leukemia/small lymphocytic lymphoma

BACKGROUND

Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are regarded as the same entity, with SLL restricted to tissue cases featuring no leukemic phase. In this study, the authors evaluate a group of SLL cases for cytogenetic abnormalities and IgVH gene mutational status to illicit differences between CLL and SLL.

DESIGN

IgVH gene polymerase chain reaction amplification and subsequent sequencing were preformed on formalin-fixed, paraffin-embedded archival tissue of 44 patients (SLL n = 34 or CLL n = 10). Cytogenetic data, CD38, and ZAP-70 expression were also evaluated for these cases.

RESULTS

The data indicate that 9/34 (26%) SLL cases have somatic hypermutation >2%, which is less than the CLL group where 40% were mutated (4/10). Cytogenetic abnormalities were seen in 58% of the SLL cases with many showing abnormalities associated with favorable to intermediate prognosis.

CONCLUSION

The authors' attempt to compare CLL with SLL with regards to cytogenetic and IgVH mutational status shows no statistically significant difference.

CD5-positive chronic B-cell lymphoproliferative disorders: diagnosis and prognosis of a heterogeneous disease entity

BACKGROUND

The pathology and clinical course of patients with CD5+ chronic B-cell lymphoproliferative disorders, excluding those that present with typical chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL) or mantle cell lymphoma, (i.e. CD5+B-CLPD) are poorly defined.

METHODS

We studied patients with CD5+B-CLPD to (1) more completely define the clinical features and pathology of CD5+B-CLPD, (2) compare these features to patients presenting with typical CLL, and (3) test the hypothesis that a subset of patients with CD5+B-CLPD could have a unique B-cell malignancy.

RESULTS

We identified 229 patients with CD5+B-CLPD. A definitive pathological diagnosis was made in all 61 (27%) CD5+B-CLPD patients with nonbone marrow (BM) biopsy specimens considered adequate for a comprehensive pathological examination. The most common diagnosis among these 61 patients was CLL (44%) followed by the leukemic phase of marginal zone lymphoma (34%), lymphoplasmacytic lymphoma (11%), diffuse large B cell lymphoma (8%), and high-grade B cell lymphoma not otherwise specified (2%). In contrast, among 168 patients without a non-BM tissue biopsy specimen, a specific diagnosis could be made on review of all available data in only 24 (14%) with 144 (86%) remaining "unclassified."

CONCLUSIONS

In patients with CD5+B-CLPD, a definitive diagnosis can be made on an adequate non-BM tissue biopsy suggesting that this entity does not include a novel disease. We recommend that all patients with CD5+B-CLPD should have a non-BM tissue biopsy to make a definitive diagnosis prior to initiation of treatment.

Chronic Lymphocytic Leukemia, Small Lymphocytic Lymphoma, and Monoclonal B-Cell Lymphocytosis

Chronic lymphocytic leukemia (CLL), small lymphocytic lymphoma (SLL), and monoclonal B-cell lymphocytosis (MBL) are clonal proliferations of small, mature B cells. CLL and SLL are considered neoplastic, although they are indolent and many patients with these lymphomas never require treatment. Most MBL cases share immunophenotypic and genetic features with CLL and SLL but have a small burden of clonal cells. This review focuses on the pathologic features of CLL, SLL, and MBL and their differential diagnoses. Guidelines are provided to separate the entities from one another and to avoid pitfalls in distinguishing these entities from other lymphomas and from reactive lymphoid proliferations.

Most morphologic features in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) do not reliably predict underlying FISH genetics or immunoglobulin heavy chain variable region somatic mutational status

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is common in the Western world. Genetic abnormalities detected by fluorescence in situ hybridization (FISH) and immunoglobulin heavy chain variable gene region (IGHV) mutational status are well-known independent prognostic indicators in CLL/SLL. Given the requirement for specialized testing to detect such aberrations, we investigated whether morphologic features may predict the presence of a more or less favorable genetic profile. Forty-one SLL cases were morphologically evaluated for expanded proliferation centers, increased large cells outside of proliferation centers, and nuclear contour irregularities (NCI) in small and large tumor cells. ZAP-70 immunohistochemistry and FISH (deletions of 13q14, p53 and ATM and trisomy 12) were successful in all cases. IGHV mutational status was determined in 26/41 cases. Significant NCI in both small and large cells correlated with the presence of an unfavorable FISH abnormality (ie, ATM or p53 deletions). However, despite good specificity (94%), the sensitivity (57%) of this finding is inadequate for routine use. No other significant associations with morphologic features were identified. Strong ZAP-70 positivity correlated with unmutated IGHV (P=0.001), rendering ZAP-70 IHC a useful surrogate for IGHV mutational status. ZAP-70 positivity predicted against finding a favorable FISH deletion 13q14 (P=0.023). Although we only studied 41 cases, we corroborated their validity using Kaplan-Meier overall survival analysis. In conclusion, morphologic features in SLL are not a reliable predictor of underlying genetic status. Thus, we propose a practical, cost-effective approach to the work-up of these cases, which should be driven by clinical necessity.

The clinical and biological features of a series of immunophenotypic variant of B-CLL

OBJECTIVES

To describe the clinical and biological features of a series of immunophenotypic variant of B-CLL (v-CLL) characterised by intermediate RMH score, in the absence of t(11;14)(q13;q32) in FISH analysis in comparison with a series of typical CLL.

METHODS

We studied the clinical and biological features of 63 cases of v-CLL and 130 cases of CLL.

RESULTS

We observed significant differences in terms of age <70 yr (P < 0.001), lymphocytosis <20 x 10(9)/L (P < 0.001), lymphocyte doubling time <or=12 months (P = 0.02), high serum beta2-microglobulin levels (P < 0.001) and splenomegaly (P = 0.002); CD38, CD49d, CD1c were more expressed in v-CLL, CD43 in CLL (P < 0.001). IgV(H) mutation and trisomy 12 were more frequent in v-CLL group (P = 0.001; P < 0.001); del13q14 in CLL (P = 0.008). Gene expression profiling of nine v-CLL and 60 CLL indicated that the atypical group presented a specific molecular pattern. After a median follow-up of respectively, 55 (4-196) and 60 months (6-180), 25/42 patients with v-CLL (48%) and 55/93 patients with CLL (59%) were treated. Time to treatment was significantly shorter in IgV(H)-mutated v-CLL vs. mutated CLL (P = 0.006). The median overall survival was worse in v-CLL-mutated cases (P = 0.062).

CONCLUSION

v-CLL should be identified and dealt with separately from classic CLL. In particular, the prognostic markers that are routinely used to characterise classical B-CLL should not be interpreted as having the same meaning.

The leukemias of mature lymphocytes

The leukemias of mature B cells and T cells are a limited set of diseases in which blood and bone marrow are the primary sites of involvement. Although they may superficially resemble one another, they have distinct clinical and pathologic features and must be distinguished from one another. In this article, the major clinical, morphologic, phenotypic, and molecular genetic features of the mature B- and T-cell leukemias are reviewed, and differential diagnostic considerations are discussed.

Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue arising in the lateral ventricle

Extranodal marginal zone B-cell lymphomas of mucosa-associated lymphoid tissue (MALT) lymphomas are a well-described type of low-grade B-cell non-Hodgkin lymphoma. They typically arise adjacent to mucosal surfaces in the gastrointestinal tract, lung and conjunctiva, and, less frequently, in the skin, salivary gland and thyroid gland. Unusual locations, such as the genitourinary tract, thymus and meninges, have also been reported. We recently encountered a case of an intracranial MALT lymphoma in a 53-year-old man who presented with persistent headaches and a seizure. The lesion developed as a mass within the lateral ventricle, appeared to be arising from the choroid plexus, and was not associated with meninges. Histologically, there was a vaguely nodular, dense lymphoid infiltrate with occasional benign follicles colonized by marginal zone lymphoma, suggesting derivation from a focus of prior inflammation. Translocations involving the MALT1 gene were not identified but karyotypic evaluation highlighted a complex cytogenetic profile with many chromosomal abnormalities. This rare case provides insight into the pathophysiology of MALT lymphomas.

Deciphering leukemic B-cell chronic lymphoproliferative disorders

Diagnosis of leukemic B-cell chronic lymphoproliferative disorders (B-CLPD) is a frequent challenge in hematology. In this multicentric study, we prospectively studied 165 new consecutive leukemic patients with B-CLPD selected on the basis of Royal Marsden Hospital scoring system < or =3. The primary aim of the study was to try to decipher the atypical cases and identify homogenous subgroups. Overall, morphological examination contributed to diagnosis in only 20% cases, all of them CD5 negative. Thirty additional cases were CD5 negative suggestive of leukemic marginal zone lymphoma in most cases. The significantly poorer survival of the 26 cyclin D1 positive cases justifies recommending its systematic determination among atypical B-CLPD. CD20 expression segregated clearly two subgroups among CD5 positive cyclin D1 negative B-CLPD. The 17 patients with the CD20 dim profile represent a homogeneous subgroup very close to typical B-cell chronic lymphocytic leukemia (B-CLL) on morphological, phenotypical and cytogenetical criteria. In contrast, the subgroup of 51 patients with a CD20 bright profile is heterogeneous. Their significantly lower p27 expression level suggest the presence of a proliferative component, underlying a more aggressive disease. Further genomic studies are warranted to establish their precise nature. These cases should not be included in the same therapeutic trials as B-CLL.

2006 Bethesda International Consensus recommendations on the flow cytometric immunophenotypic analysis of hematolymphoid neoplasia: medical indications

The clinical indications for diagnostic flow cytometry studies are an evolving consensus, as the knowledge of antigenic definition of hematolymphoid malignancies and the prognostic significance of antigen expression evolves. Additionally the standard of care is not routinely communicated to practicing clinicians and diagnostic services, especially as may relate to new technologies. Accordingly there is often uncertainty on the part of clinicians, payers of medical services, diagnostic physicians and scientists as to the appropriate use of diagnostic flow cytometry. In an attempt to communicate contemporary diagnostic utility of immunophenotypic flow cytometry in the diagnosis and follow-up of patients with hematolymphoid malignancies, the Clinical Cytometry Society organized a two day meeting of international experts in this area to reach a consensus as to this diagnostic tool. This report summarizes the appropriate use of diagnostic flow cytometry as determined by unanimous approval of these experienced practitioners.

Impact of trisomy 12, del(13q), del(17p), and del(11q) on the immunophenotype, DNA ploidy status, and proliferative rate of leukemic B-cells in chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (B-CLL) is a well-defined clinical entity with heterogeneous molecular and cytogenetic features. Here, we analyze the impact of trisomy 12, del(13q), del(17p), and del(11q) as determined by interphase fluorescence in situ hybridization analysis of purified neoplastic B-CLL cells on their immunophenotype, DNA ploidy status and proliferative rate.Overall, 111 of 180 (62%) B-CLL cases studied displayed one (50%) or more (12%) genetic abnormalities, del(13q) (35%) being more frequently detected than trisomy 12 (23%) followed by del(11q) (9%) and del(17p) (8%). Trisomy 12 was associated with a higher frequency of DNA aneuploidy, stronger expression of CD19, CD20, CD22, CD24, CD27, CD79b, CD38, and sIg and lower reactivity for CD43 with respect to cytogenetically nonaltered cases. In turn, cases with del(13q) displayed greater reactivity for CD20, FMC7, CD27, CD22, CD5, and bcl2, while del(11q) was associated with brighter expression of CD38, FMC7, CD25, and sIg. Hierarchical clustering analysis of the immunophenotype of B-CLL cases with cytogenetic abnormalities allowed the identification of three different groups of patients with increasing frequencies of trisomy 12, del(11q), and del(13q). Remarkably, none of the cytogenetic abnormalities analyzed except coexistence of 13q- and 17p- had a clear impact on the proliferative index of B-CLL cells.

Pathology of chronic lymphocytic leukemia: an update

Chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) is a clonal lymphoproliferative disorder characterized by proliferation of morphologically and immunophenotypically mature lymphocytes. CLL/SLL may proceed through different phases: an early phase in which tumor cells are predominantly small in size, with a low proliferation rate and prolonged cell survival, and a transformation phase with the frequent occurrence of extramedullary proliferation and an increase in large, immature cells. Although some patients with CLL have an indolent disease course and die after many years of unrelated causes, others have very rapidly disease progression and die of the disease within a few years of the diagnosis. In the past few years, considerable progress has been made in our ability to diagnose and classify CLL accurately. Through cytogenetics and molecular biology, it has been shown that CLL and variants are associated with a unique genotypic profile and that these genetic lesions often have a direct bearing on the pathogenesis and prognosis of the disease. Similarly, the development of antibodies to new biologic markers has allowed the identification of a unique immunophenotypic profile for CLL and variants. Moreover, accumulating evidence suggests that CLL cells respond to selected microenvironmental signals and that this confers a growth advantage and an extended survival to CLL cells. In this article, we will review the progress in the pathobiology of CLL and give an update on prognostic markers and tools in current pathology practice for risk stratification of CLL.

Comparative analysis of ZAP-70 expression and Ig VH mutational status in B-cell chronic lymphocytic leukemia

BACKGROUND

B-cell chronic lymphocytic leukemia (CLL) is a heterogeneous disorder with respect to its clinical course. Accurate identification of prognostic factors is becoming increasingly important in order to determine those patients requiring aggressive treatments. Two of the most predictive outcome markers are the Ig VH mutational gene status and ZAP-70 expression. In earlier reports, both parameters have shown a high degree of concordance. To assess the value of these determinations in clinical practice, we simultaneously analyzed Ig VH mutations and ZAP-70 expression in a consecutive series of B-CLL.

METHODS

Fifty-three consecutive B-CLL cases were included in the study. ZAP-70 expression was investigated by flow cytometry. Positivity was established using two methods: comparing ZAP70 expression in B-cells with T-cells using cytoplasmic CD3 (ZAP-70/T) and with NK-cell reactivity (ZAP-70/NK). The complete immunophenotype was recorded in each case. Ig VH mutational gene status was determined employing purified RNA from peripheral blood samples. Retrotranscribed DNA was PCR-amplified, direct-sequenced, and compared with available public databases. VH3.21 family use was also recorded.

RESULTS

Using a T-cell marker, 58% of patients were ZAP-70+ and 42% were ZAP-70-. NK-cell comparisons gave only 6% of ZAP-70 positivity in B-CLL, and in six cases the absence of a clearly defined NK-cell population precluded the ZAP70 analysis. Twenty-four (45%) patients had mutated Ig VH genes and 29 (55%) had unmutated Ig VH genes. The results showed a statistical association between ZAP-70/T expression and VH mutational status. Despite this, in 30% of cases there was a discordant result. Immunophenotypic analysis showed no major differences in Matutes'score between mutated and nonmutated cases. Only FMC7 was more commonly expressed in the unmutated B-CLL cases. VH3.21 was present in 7.5% of cases, mostly having an unmutated pattern.

CONCLUSIONS

ZAP-70 reactivity using a T-cell marker as a control allows to identify the majority of patients with an unmutated Ig VH genotype. Parallel analysis revealed that discordances with Ig VH analysis are quite common with currently employed flow cytometry reagents and techniques.

A scoring system based on the expression of six surface molecules allows the identification of three prognostic risk groups in B-cell chronic lymphocytic leukemia

We have previously identified 12 surface antigens whose differential expression represented the signature of B-cell chronic lymphocytic leukemia (B-CLL) subsets with different prognosis. In the present study, expression data for these antigens, as determined in 137 B-CLL cases, all with survivals, were utilized to devise a comprehensive immunophenotypic scoring system of prognostic relevance for B-CLL patients. In particular, univariate z score was employed to identify the markers with greater prognostic impact, while maximally selected log-rank statistics were chosen to define the optimal cut-off points capable to split patients into two groups with different survivals. A weighted immunophenotypic scoring system was developed by integrating results from these analyses. Six antigens were selected: three positive prognosticators (CD62L, CD54, CD49c) and three negative prognosticators (CD49d, CD38, CD79b), with cut-off values ranging from 30% to 50% of positive cells. By weighing the expression of each marker according to its statistical power, a complete scoring system, with point values comprised between 0 (complete absence of phenotypic conditions associated with good prognosis) and 9 (all the phenotypic conditions associated with good prognosis fulfilled), allowed to split the whole set of B-CLL patients, into three distinctive prognostic groups (P = 4.78 x 10(-11)) with high- (score 0-3), intermediate- (score 4-6), and low- (score 7-9) risk of death. The three risk groups showed different distribution of cases as for Rai's stages, IgVH mutations, and ZAP-70 expression. The proposed immunophenotypic scoring system may be an additional useful tool in routine diagnostic/prognostic procedures for B-CLL.

Trisomy 12-associated, t(11;14)-negative mature B-cell leukemia with gene expression profile resembling mantle cell lymphoma

Trisomy 12 can be seen in many different lymphoid neoplasms. However, many or most mature B-cell leukemias associated with isolated trisomy 12 are reported in the literature as chronic lymphocytic leukemia (CLL) or 'atypical CLL'. This study reports a case of a mature B-cell leukemia, morphologically and immunophenotypically similar to cases previously published as atypical CLL, in which cytogenetic evaluation revealed an isolated clonal trisomy 12 but no evidence of the mantle cell lymphoma-associated t(11;14)(q13;q32). Further analysis confirmed absence of cyclin-D1 expression. Subsequent lymph node biopsy revealed evidence of large cell transformation of the underlying chronic lymphoproliferative disorder. Gene expression profiling of the initial peripheral blood sample using a cDNA micro-array of approximately 10,000 expressed genes revealed a close resemblance between the reported case and 2 cases of known mantle cell lymphoma. When further compared to 7 known 'typical' CLL cases, the reported case was classified as mantle cell lymphoma by hierarchical cluster analysis. The case reported here raises interesting questions regarding the nature of cases reported previously as trisomy 12-associated CLL and reinforces the fact that other leukemic lymphoproliferative disorders should be included in the differential diagnosis of such cases. Further study is indicated to elucidate the nature and diversity of disorders previously reported as trisomy 12-associated chronic lymphocytic leukemia.

Use of a blocking antibody method for the flow cytometric measurement of ZAP-70 in B-CLL

BACKGROUND

In this study we developed a method to measure the amount of ZAP-70 [zeta accessory protein] in B-CLL cells without relying on the ZAP-70 expression of patient B or T cells to normalize fluorescence intensity.

METHODS

B-CLL cells were fixed with formaldehyde before surface staining with gating antibodies CD19PC5 and CD5FITC. The cells were permeabilized with saponin, and the ZAP-70 antigen was blocked in one tube with unlabeled antibody to ZAP-70 [clone 1E7.2]. Zap-70-PE was then added to this tube. ZAP-70-PE was added to a second tube without unlabeled antibody to ZAP-70. The mean fluorescence intensity of the ZAP-70 in the tube without unlabeled antibody divided by the mean fluorescence intensity of the ZAP-70 in the tube with unlabeled antibody equals the RATIO of total fluorescence to non-specific ZAP-70 fluorescence in the B-CLL cells. In a second method of analysis, a region is created in the histogram showing ZAP-70 fluorescence intensity in the tube with unlabeled antibody to ZAP-70. This region is set to 0.9% positive cells. This same region is then used to measure the % positive [%POS] ZAP-70 cells in the tube without unlabeled antibody to ZAP-70. The brighter the ZAP-70 fluorescence above the non-specific background, the higher the %POS.

RESULTS

Due to the varying amount of non-specific staining between patient B-CLL cells and other cells, the blocking antibody method yielded a more quantitative and reproducible measure of ZAP-70 in B-CLL cells than other methods, which use the ratio of B-CLL fluorescence to normal B or T-cell fluorescence. Using this improved method, ZAP-70 was determined to be negative if the RATIO was less than 2:1 and positive if the RATIO was greater than 2:1. ZAP-70 was determined to be negative if the %POS was less than 5% and positive if the %POS was greater than 5%, a cut-off value lower than previous values published, due to exclusion of non-specific staining. Both cut-offs were based upon patient specimen distribution profiling.

CONCLUSIONS

Use of a blocking antibody resulted in a robust, reproducible clinical B-CLL assay that is not influenced by the need to measure the amount of ZAP-70 in other cells. ZAP-70 results segre gate patients into indolent and aggressive groups suggested by published clinical outcomes.

Applications of Flow Cytometry and Immunohistochemistry to Diagnostic Hematopathology

Objective.—Diagnostic hematopathology depends on the applications of flow cytometric immunophenotyping and immunohistochemical immunophenotyping combined with the cytomorphology and histologic features of each case. Select cases may require additional ancillary cytogenetic and molecular studies for diagnosis. The purpose of this review is to focus on the applications of flow cytometric and immunohistochemical immunophenotyping of paraffin-embedded tissue to diagnostic hematopathology. Advantages and disadvantages of these techniques are examined.

Data Sources.—The literature is extensively reviewed (PubMed 1985–2003) with an emphasis on the most recent applications and those that are most useful clinically, both diagnostically and prognostically.

Study Selection.—Studies were selected based on statistically significant results in large studies with reported adequate clinical follow-up.

Data Extraction.—The methodology was reviewed in the selected studies to ensure reliable comparison of reported data.

Data Synthesis.—Flow cytometric immunophenotyping offers the sensitive detection of antigens for which antibodies may not be available for paraffin immunohistochemical immunophenotyping. However, paraffin immunohistochemical immunophenotyping offers preservation of architecture and evaluation of expression of some proteins, which may not be available by flow cytometric immunophenotyping. These techniques should be used as complimentary tools in diagnostic hematopathology.

Conclusions.—There are extensive applications of flow cytometric and immunohistochemical immunophenotyping to diagnostic hematopathology. As cytogenetic and molecular findings evolve in diagnostic hematopathology, there may be additional applications of flow cytometric and immunohistochemical immunophenotyping to this field of pathology.

Advances in the diagnosis and classification of chronic lymphoproliferative disorders

In this review, we have highlighted recent advances in chronic lymphoproliferative disorders that commonly involve the peripheral blood. As we have seen, our concepts of certain diseases are changing. Molecular genetic and immunophenotypic studies are allowing more precise characterization of CLL and defining important biologic markers that predict clinical behavior. Prolymphocytic leukemia is now more narrowly defined and its relationship to nucleolated variants of MCL is now apparent. With new reagents and techniques applied to problems such as identification of Sezary cells and T-cell monoclonality determination, our ability to diagnose, monitor, and provide prognostic information is improving. Insight into the biology of these diseases also may provide new therapeutic targets in the future.

Update in the pathologic features of mature B-cell and T/NK-cell leukemias

Modern diagnosis of mature B- and T-cell leukemias requires integration of morphologic, immunophenotypic, and molecular genetic features. This integrative approach has allowed more precise definitions of specific disease entities. This in turn provides better information for clinicians to select proper therapy and determine prognosis. The characteristic pathologic features of these disorders are reviewed.

CD79b expression in chronic lymphocytic leukemia. Association with trisomy 12 and atypical immunophenotype

CONTEXT

CD79b is a relatively newly characterized B-cell marker that is expressed in a minority of chronic lymphocytic leukemia (CLL) cases.

OBJECTIVE

To systematically correlate CD79b expression with specific morphologic and immunophenotypic findings and trisomy 12.

DESIGN

We assessed CD79b expression in 100 consecutively accrued CLL cases that were also analyzed by conventional cytogenetics. Based on the association between trisomy 12 and CD79b expression, we then assessed 43 additional CLL cases with trisomy 12. CD79b expression was correlated with morphology and expression of other immunophenotypic markers.

RESULTS

Eighteen (18%) of 100 consecutively accrued cases were CD79b positive. No significant association was found between CD79b expression and atypical morphology. CD79b expression correlated with CD22 and FMC7 positivity. Eight (8%) cases had trisomy 12; 4 (50%) of these were CD79b positive, suggesting an association with trisomy 12. Examination of a second group of 51 CLL cases with trisomy 12 (including 8 cases from the initial study group) showed that CD79b was positive in 26 cases (49%), a frequency significantly higher than that of the consecutively accrued CLL cases without trisomy 12 (P <.05).

CONCLUSIONS

We conclude that CD79b immunoreactivity is positive in approximately 20% of CLL cases and that expression correlates with trisomy 12 and atypical immunophenotypic findings.

Biological and clinical heterogeneity of B-cell chronic lymphocytic leukemia

B-cell chronic lymphoproliferative disorders have been recognized as a heterogeneous group of neoplastic diseases affecting the lymphoid system. They are frequently characterized by leukemic manifestations with peripheral blood and/or bone marrow involvement. B-cell chronic lymphocytic leukemia (B-CLL), a disease which is now accepted as derived from immunologicallycompetent antigen-activated B-cells, is the most common in the western countries. Although for several decades it was considered as a unique entity, a body of evidences is now emerging indicating the biological heterogeneity of B-CLL. Molecular and immunophenotypic data induce to consider two main subgroups of B-CLL exist at the cellular level: in fact, B-CLL cases can be divided into two categories according to IgV gene mutation status. One group develops from "memory" B-cells after antigenic stimulation in the germinal center of secondary follicles, displays mutated gene IgV and lacks CD38 expression; the second one derives from the so-called "naïve" antigen inexperienced B-cells, does not present IgV gene mutations and displays CD38 surface molecule. The two groups seem to be characterised by different clinical outcomes with the "mutated" group expected to have a more benign course than that arising from a "naïve" B-cell. Thus, the definition of the biological features of these different groups could be of help for clinicians in order to recognize patients needing more intensive therapeutic approaches.