[Interpretation of lymphoid proliferations and lymphomas associated with immune deficiency and dysregulation in the 5th edition WHO classification of haematolymphoid tumours].

The fifth edition of the World Health Organization (WHO) classification of lymphohematopoietic system tumors updated the terminology, types of lesions, diagnostic criteria, nomenclature, and other aspects of lymphoid proliferations and lymphomas associated with immune deficiency and dysregulation. The important updates and main changes in this section were briefly introduced, in order to guide the precise classification of lymphoid proliferations and lymphomas associated with immune deficiency and dysregulation, and standardize pathological reports.

[Interpretation of T-cell and NK-cell lymphoid proliferations and lymphomas in the 5th edition of the WHO classification of haematolymphoid tumours].

The 5th edition of the World Health Organization (WHO) classification of haematolymphoid tumours used the hierarchical system to classify T-cell and NK-cell lymphoid proliferations and lymphomas (T/NK-LPD/LYM) based on research advances and clinicopathological characteristics of the diseases. In this edition of classification, tumour-like lesions were included, some tumors were added/deleted, the names or terms of certain diseases were refined, and the diagnostic criteria or subtypes of some diseases were revised. This group of diseases was reintegrated from non-clonal hyperplasia to highly aggressive lymphoma, which would further reflect the nature of T/NK-LPD/LYM and benefit to clinical application.

New developments in non-Hodgkin lymphoid malignancies.

The revised fourth edition of the World Health Organization (WHO) Classification of Tumours of Haematopoietic and Lymphoid Tissues (2017) reflects significant advances in understanding the biology, genetic basis and behaviour of haematopoietic neoplasms. This review focuses on some of the major changes in B-cell and T-cell non-Hodgkin lymphomas in the 2017 WHO and includes more recent updates. The 2017 WHO saw a shift towards conservatism in the classification of precursor lesions of small B-cell lymphomas such as monoclonal B-cell lymphocytosis, in situ follicular and in situ mantle cell neoplasms. With more widespread use of next generation sequencing (NGS), special entities within follicular lymphoma and mantle cell lymphoma were recognised with recurrent genetic aberrations and unique clinicopathological features. The diagnostic workup of lymphoplasmacytic lymphoma and hairy cell leukaemia has been refined with the discovery of MYD88 L265P and BRAF V600E mutations, respectively, in these entities. Recommendations in the immunohistochemical evaluation of diffuse large B-cell lymphoma include determining cell of origin and expression of MYC and BCL2, so called 'double-expressor' phenotype. EBV-positive large B-cell lymphoma of the elderly has been renamed to recognise its occurrence amongst a wider age group. EBV-positive mucocutaneous ulcer is a newly recognised entity with indolent clinical behaviour that occurs in the setting of immunosuppression. Two lymphomas with recurrent genetic aberrations are newly included provisional entities: Burkitt-like lymphoma with 11q aberration and large B-cell lymphoma with IRF4 rearrangement. Aggressive B-cell lymphomas with MYC, BCL2 and/or BCL6 rearrangements, so called 'double-hit/triple-hit' lymphomas are now a distinct entity. Much progress has been made in understanding intestinal T-cell lymphomas. Enteropathy-associated T-cell lymphoma, type II, is now known to not be associated with coeliac disease and is hence renamed monomorphic epitheliotropic T-cell lymphoma. An indolent clonal T-cell lymphoproliferative disorder of the GI tract is a newly included provisional entity. Angioimmunoblastic T-cell lymphoma and nodal T-cell lymphomas with T-follicular helper phenotype are included in a single broad category, emphasising their shared genetic and phenotypic features. Anaplastic large cell lymphoma, ALK- is upgraded to a definitive entity with subsets carrying recurrent rearrangements in DUSP22 or TP63. Breast implant-associated anaplastic large cell lymphoma is a new provisional entity with indolent behaviour. Finally, cutaneous T-cell proliferations include a new provisional entity, primary cutaneous acral CD8-positive T-cell lymphoma, and reclassification of primary small/medium CD4-positive T-cell lymphoma as lymphoproliferative disorder.

Comparison of Systemic EBV-positive T-Cell and NK-Cell Lymphoproliferative Diseases of Childhood Based on Classification Evolution: New Classification, Old Problems.

Systemic Epstein-Barr virus-positive T-cell and natural killer (NK)-cell lymphoproliferative diseases of childhood are a group of lethal diseases mostly affecting children and young adults. The Ohshima Grading System and the 2017 World Health Organization (WHO) classification have been used for classifying this spectrum, but these systems have not been validated externally and compared. Therefore, we examined 36 cases of systemic Epstein-Barr virus-positive T-cell and NK-cell lymphoproliferative diseases of childhood with long-term follow-up, from Southwest China, to systematically summarize the clinicopathologic features and to validate and compare the Ohshima Grading System and the 2017 WHO classification in discrimination ability, predictive accuracy, concordance indices, and explained variation. Clinically, our cohort showed severe manifestations and poor prognoses. Morphologically, the hematopoietic and lymphoid specimens showed proliferation of small-sized to medium-sized bland-looking lymphocytes that might mask disease severity, whereas other extranodal lesions showed a disorganized to obliterated architecture infiltrated by medium-sized to large-sized, subtle to obvious atypical cells, which may mimic extranodal NK/T-cell lymphoma. Immunophenotypically, our cases mainly originate from CD8 αß T cells. Therefore, clinical and pathologic features should be equally considered to avoid missed diagnosis or misdiagnosis. In addition, the 2017 WHO classification shows a flexible grasp of pathologic features, thus classifying some cases (polymorphic and monoclonal cases with fulminant course) more reasonably; thereby, it showed statistically improved results compared with the Ohshima Grading System. However, underestimating the risk of some polyclonal cases and imprecisely discriminating monoclonal cases at diagnosis are common dilemmas in both systems. Therefore, the construction of a comprehensive grading algorithm for improved prognostic value and precise diagnosis requires additional studies.

The broad and challenging landscape of extranodal lymphoproliferations.

Two sessions in the workshop of the 19th meeting of the European Association for Haematopathology termed "challenging extranodal lymphoproliferations" and "extranodal non-site-specific lymphoproliferations", dealt with a series of heterogenous cases. These included lymphoproliferations of all cell lineages, from reactive lesions mimicking lymphomas through indolent lymphoid neoplasia and tumours with unclear biological behaviour to aggressive and transformed lymphomas. The themes addressed included cases with borderline features between hyperplastic and neoplastic lesions, the diagnostic spectrum of IgG4-related disease, T cell lymphoproliferations arising in extranodal sites with presumed indolent behaviour, diverse clinical presentations of intravascular large B cell lymphoma, diagnostic problems encountered with tumours displaying plasmablastic morphology, pitfalls concerning rare entities like adult T cell lymphoma/leukaemia (ATLL) and extranodal natural killer/T cell (NK/T) lymphomas, and unusual clinical presentations of various lymphomas. Altogether, within the frame of these two sessions, 75 cases remarkably differing in their clinical background, genetic features and overall need for a meticulous diagnostic approach were presented and discussed. In this paper, the salient points raised during the discussion of the cases, current diagnostic concepts and recommendations relevant to the diagnosis of these lymphoproliferations are described.

The clinico-pathological spectrum of primary cutaneous lymphoma other than mycosis fungoides/Sezary syndrome.

The major aim of Session 1 of the 2018 European Association of Hematopathology/Society for Hematopathology Workshop was to collect examples of cutaneous lymphomas, excluding mycosis fungoides/Sezary syndrome, as defined in the current WHO classification of tumours of the haemetopoietic and lymphoid tissues. Overall 42 cases were submitted. These were considered in four main categories: primary cutaneous B cell lymphomas (12 cases), primary cutaneous T cell lymphomas/lymphoproliferations with CD8+/cytotoxic phenotype (12 cases), primary cutaneous CD30-positive lymphoproliferative disorders (15 cases) and primary cutaneous T cell lymphomas/leukaemias with CD4+ phenotype (4 cases). Using these cases as examples, we were able to present the full spectrum of cutaneous lymphoproliferations (excluding mycosis fungoides/Sezary syndrome), including examples of rare, provisional and new entities as listed in the 2017 update of the WHO classification. The findings are summarized in this report with emphasis on differential diagnostic considerations and the importance of clinico-pathological correlation for final subtyping. In presenting these findings we hope to raise awareness of this enigmatic group of neoplasms and to further our understanding of these rare disease entities.

[Histopathological classification of chronic B-lymphoproliferative disorders]. / Classification anatomopathologique des syndromes lymphoprolifératifs B chroniques.

Chronic lymphoproliferative disorders should be classified according to the revised 2016 WHO classification. Biopsies are not mandatory for all chronic lymphoproliferative disorders as blood or bone marrow cytologroachical approach can be sufficient for some lymphoma entities. Diagnostic is based on a multidiscplinary approach taking into account clinical presentation, histopathological, cytological, immunophenotypical features (immunohistochemistry and Flow cytometry) and molecular pattern (translocation by FISH, Mutations landscape by NGS, and genomic abnormalities by CGH array). An important heterogeneity of clinical presentation and prognosis arises within the same lymphoma subtype. Clinical evolution is characterized by relapses, cytological progression and transformation into diffuse large B cell lymphoma, aggressive lymphoma or high-grade lymphomas.

EBV-Associated Lymphoproliferative Disorders: Update in Classification.

Although about 90% of the world's population is infected by EBV only a small subset of the related infections result in neoplastic transformation. EBV is a versatile oncogenic agent involved in a multitude of hematopoietic, epithelial, and mesenchymal neoplasms, but the precise role of EBV in the pathogenesis of many of the associated lymphoid/histiocytic proliferations remains hypothetical or not completely understood. Additional studies and use of evolving technologies such as high-throughput next-generation sequencing may help address this knowledge gap and may lead to enhanced diagnostic assessment and the development of potential therapeutic interventions.

PD-L1 and PD1 expression in post-transplantation lymphoproliferative disease (PTLD) of childhood and adolescence: An inter- and intra-individual descriptive study covering the whole spectrum of PTLD categories.

Therapy of children with post-transplantation lymphoproliferative disorder (PTLD) after hematopoietic stem cell (HSCT) and solid organ transplantation (SOT) can be challenging. In this retrospective study, we investigated PD-L1 and PD1 expression in all PTLD categories of childhood and adolescence to see whether checkpoint inhibition with PD-L1/PD1 inhibitors may serve as a therapy option. We included 21 patients aged 19 years or younger (at date of transplant) with PTLD following SOT or HSCT having adequate tumor samples available (n = 29). Using immunohistochemistry, we evaluated PD-L1/PD1 expression on both tumor cells and cells of the microenvironment in all samples. Availability of consecutively matched tumor samples during 6 of 21 patients' disease courses also allowed an intra-individual assessment of PD-L1/PD1 expression. We observed lower PD-L1 and higher PD1 expression in non-destructive lesions, and higher PD-L1 and lower PD1 expression in polymorphic and, in particular, in monomorphic PTLD, mostly diffuse large B-cell lymphomas (DLBCL, n = 10/21). The amount of PD-L1- and PD1-positive cells changed in the opposite way in sequential biopsies of the same individual correlating well with the PTLD category. This is the first comprehensive pediatric study assessing PD-L1 and PD1 expression on tumor cells and in the microenvironment of PTLD including not only monomorphic, but also non-destructive early lesions. PD-L1 expression of the tumor cells inversely correlated with PD1 expression in surrounding tissues, with the highest expression in DLBCL. Since PTLD can be therapeutically challenging, our results indicate a potential efficacy of checkpoint inhibitors if standard immune- and/or chemotherapy fail or are impossible. We therefore recommend routine staining of PD-L1 and PD1 in all PTLD categories.

Iatrogenic immunodeficiency-associated lymphoproliferative disorders of B-cell type that develop in patients receiving immunosuppressive drugs other than in the post-transplant setting.

In the current revised 4th edition of the World Health Organization (WHO) classification, 'other iatrogenic immunodeficiency-associated lymphoproliferative disorders (Oii-LPDs)' is listed in the last section in the chapter on immunodeficiency-associated lymphoproliferative disorders. Oii-LPDs cover a broad spectrum from benign lesions to lymphoma, and correspond to one of the subtypes in the WHO classification for immunocompetent patients.The WHO classification does not clearly indicate the histological subtype of this disease category; however, the framework of subtype classification is similar to the classification of post-transplant lymphoproliferative disorders, and recent studies have attempted to subcategorize Oii-LPDs that fit this unique disease type. In this review, we provide an overview of B-cell-type Oii-LPDs regarding their histopathology and immunophenotype, genetics and clinical behaviors.

Criterios diagnósticos y nuevas opciones terapéuticas para los pacientes con diagnóstico de linfoma no Hodgkin / Diagnostic criteria and new therapeutic options for patients diagnosed with non-Hodgkin lymphoma

Fundamento: las hemopatías malignas día a día aumentan su incidencia y proliferación dentro de la población, entre ellas el síndrome linfoproliferativo ocupa un lugar importante, es un grupo de trastornos de origen clonal, que afecta a las células linfoides, con características heterogéneas desde el punto de vista clínico, histológico y molecular. Objetivo: agrupar diferentes criterios diagnósticos y divulgar nuevas opciones terapéuticas para los pacientes con diagnóstico de linfoma no Hodgkin.Métodos: se realizó una búsqueda bibliográfica en las plataformas de acceso a bases de datos de la red de información de salud cubana Infomed, dentro de ellas en EBSCOhost, PubMed/Medline y SciELO. Se utilizaron los siguientes descriptores: síndromes linfoproliferativos, linfomas, linfoma no Hodgkin.Resultados: se aborda la evolución histórica de los síndromes linfoproliferativos desde su descripción inicial hasta el momento actual, así como las diferentes clasificaciones, los tratamientos convencionales utilizados y una panorámica de las investigaciones que se realizan en busca de nuevos tratamientos. Conclusiones: la clasificación de los linfomas no Hodgkin ha cambiado a lo largo del tiempo, la extensión de la enfermedad tiene un papel fundamental en la selección del tratamiento y posible sobrevida del paciente. Existe una amplia variedad de prometedores agentes en desarrollo disponibles para el tratamiento del linfoma folicular(AU)

Background: malignant haemopathies increase their incidence and proliferation within the population, among them the lymphoproliferative syndrome occupies an important place, it is a group of disorders of clonal origin, which affects the lymphoid cells, with heterogeneous characteristics from the point of clinical, histological and molecular view. Objective:to group different diagnostic criteria and to disclose new therapeutic options for patients diagnosed with non-Hodgkin's lymphoma. Methods: a bibliographic search was carried out in the access platforms to databases of the Infomed Cuban health information network, within them in EBSCOhost, PubMed / Medline and SciELO. The following descriptors were used: lymphoproliferative syndromes, lymphomas, non-Hodgkin's lymphoma. Results: the historical evolution of the lymphoproliferative syndromes is addressed from its initial description to the present time, as well as the different classifications, the conventional treatments used and an overview of the research carried out in search of new treatments.Conclusions:the classification of non-Hodgkin lymphomas has changed over time; the extent of the disease has a fundamental role in the selection of treatment and possible survival of the patient. There is a wide variety of promising developing agents available for the treatment of follicular lymphoma(AU)

A clinicopathologic study of the spectrum of systemic forms of EBV-associated T-cell lymphoproliferative disorders of childhood: A single tertiary care pediatric institution experience in North America.

BACKGROUND: Systemic forms of EBV-associated T-cell lymphoproliferative disorders of childhood (S-EBV-T-LPD) comprise three major forms: EBV-positive hemophagocytic lymphohistiocytosis (EBV-HLH), systemic EBV-positive T-cell lymphoma (S-EBV-TCL), and systemic chronic active EBV infection (S-CAEBV). These disorders occur rarely in children in Western countries. Here, we described eight children of such entities. DESIGN: Eight cases (six clinical and two autopsy) with S-EBV-T-LPD of childhood were retrospectively identified from 1990 to 2015. Clinicopathologic parameters including histomorphology, immunophenotype, EBV studies, and T-cell receptor gene rearrangement studies were recorded. RESULTS: Patients include five females and three males of Hispanic, Asian, and Caucasian origins with an age range of 14 months to 9 years. Fever, hepatosplenomegaly, cytopenias, abnormal EBV serologies, and very high EBV viral loads were common findings. Histologic findings showed EBV+ T-cell infiltrates with variable degrees of architectural distortion and cytologic atypia ranging from no to mild cytologic atypia to overt lymphoma and tissue hemophagocytosis. All showed aberrant CD4+ or CD8+ T cells with dim to absent CD5, CD7, and CD3, and bright CD2 and CD45 by flow cytometry or loss of CD5 by immunohistochemistry. TCR gene rearrangement studies showed monoclonal rearrangements in all clinical cases (6/6). Outcomes were poor with treatment consisting of chemotherapy per the HLH-94 or HLH-2004 protocols with or without bone marrow transplant. CONCLUSION: In this large pediatric clinicopathologic study of S-EBV-T-LPD of childhood in the United States, EBV-HLH, S-EBV-TCL, and S-CAEBV show many overlapping features. Diagnosis is challenging, and overall outcome is poor using current HLH-directed therapies.

Cutaneous Lymphoproliferative Disorders: What's New in the Revised 4th Edition of the World Health Organization (WHO) Classification of Lymphoid Neoplasms.

Cutaneous lymphoproliferative disorders remain a challenging aspect of dermatopathology, in part due to the rarity of the entities and extreme variability in clinical outcomes. Although many of the entities remain unchanged, the approach to some of them has changed in the new 2016 classification scheme of the World Health Organization. Chief among these are Epstein-Barr virus-associated lymphoproliferative disorders such as Epstein-Barr virus-associated mucocutaneous ulcer and hydroa vacciniforme-like lymphoproliferative disorder, primary cutaneous CD8+ aggressive epidermotropic cytotoxic T-cell lymphoma, primary cutaneous acral CD8+ T-cell lymphoma, primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder, and breast implant-associated anaplastic large cell lymphoma. In addition, translocations and gene rearrangements such as those involving the 6p25.3 locus have started to inform diagnosis and classification of anaplastic large cell lymphoma and lymphomatoid papulosis. In this review, we will examine what is new in the diagnostic toolbox of cutaneous lymphoproliferative disorders.

Different causes of early and late-onset post transplant lymphoproliferative disorder in kidney transplantation patients after 2000.

BACKGROUND: The purpose of this study was to analyze the link between PTLD incidence and its occurrence time in patients at a single center in comparable medical environments after 2000. METHODS: Retrospectively, total 3305 kidney transplantation patients medical data were analyzed. Patients were divided into two groups based on the period from the day of kidney transplantation to the day of PTLD diagnosis. Early-onset was defined as PTLD development within two years after transplantation, whereas all other cases were categorized as late-onset PTLD. RESULTS: In the early-onset group, young age (0-19 years) was confirmed as a risk factor for PTLD incidence (HR 1.49, p = 0.038). In the late-onset group, history of anti-rejection therapy was confirmed as a risk factor (HR 1.32, p = 0.031). Overall survival rates were not significantly different between the two groups (p = 0.556). Graft survival rates were also not different between the two groups (p = 0.549). CONCLUSION: When patients with PTLD were classified into early-onset group and late-onset group at two years, overall survival and graft survival were comparable. And patients with early-onset PTLD are more likely to be associated with EBV, the late-onset patients are more likely to be immunosuppressed.

Immunodeficiency-associated lymphoproliferative disorders: time for reappraisal?

Immunodeficiency-associated lymphoproliferative disorders (IA-LPDs) are pathologically and clinically heterogeneous. In many instances, similar features are shared by a spectrum of IA-LPDs in clinically diverse settings. However, the World Health Organization (WHO) classifies IA-LPDs by their immunodeficiency setting largely according to the paradigm of posttransplant lymphoproliferative disorders but with inconsistent terminology and disease definitions. The field currently lacks standardization and would greatly benefit from thinking across immunodeficiency categories by adopting a common working vocabulary to better understand these disorders and guide clinical management. We propose a 3-part unifying nomenclature that includes the name of the lesion, associated virus, and the specific immunodeficiency setting for all IA-LPDs. B-cell lymphoproliferative disorders (LPDs) are usually Epstein-Barr virus (EBV)+ and show a spectrum of lesions, including hyperplasias, polymorphic LPDs, aggressive lymphomas, and, rarely, indolent lymphomas. Human herpes virus 8-associated LPDs also include polyclonal and monoclonal proliferations. EBV- B-cell LPDs and T- and NK-cell LPDs are rare and less well characterized. Recognition of any immunodeficiency is important because it impacts the choice of treatment options. There is an urgent need for reappraisal of IA-LPDs because a common framework will facilitate meaningful biological insights and pave the way for future work in the field.

[EB virus-positive T/NK lymphoproliferative diseases: an analysis of 156 patients].

Objective: To investigate the clinicopathological features of EBV-positive T/NK cell lymphoproliferative diseases (EBV(+) T/NK-LPD). Methods: The clinical characteristics of 156 cases of EBV(+) T/NK-LPD were collected from August 2002 to March 2015 at Beijing Friendship Hospital, Capital Medical University. Immunohistochemical staining, EBER in situ hybridization and clonal analysis of TCR gene were performed. All patients were followed up. Results: There were 106 male and 50 female patients; patients' age ranged from 1 to 75 years (median 20 years). The course of the diseases before diagnosis ranged from 2 to 540 months (median 20 months). Fever was noted in 122 patients (78.2%), 108 patients had lymphadenopathy (69.2%), and 75 patients had hepatosplenomegaly (48.1%). Thirty-three cases were grade 1, 68 cases were grade 2, and 55 cases were grade 3. TCR gene arrangement analysis was performed in 45 cases, and 33 cases (73.3%) showed clonal rearrangement. The follow-up period ranged from 1-134 months, and 44 patients (28.2%) died. There was a trend of increased death rate associated with increasing grade (P>0.05). Conclusions: There are many types of EBV(+) T/NK-LPD, and they can be classified as systemic, relatively localized and localized. The prognosis should be based on a comprehensive analysis of pathology and clinical data. There is no significant correlation between morphological grade and mortality. An important goal of therapy is to prevent serious complications.

The 2017 WHO update on mature T- and natural killer (NK) cell neoplasms.

Over the last decade, there has been a significant body of information regarding the biology of the lymphoid neoplasms. This clearly supports the need for updating the 2008 WHO (World Health Organization) classification of haematopoietic and lymphoid tumours. The 2017 WHO classification is not a new edition but an update and revision of the 4th edition. New provisional entities but not new definitive entities are included, and novel molecular data in most of the entities and changes in the nomenclature in few of them have been incorporated. In the context of the mature T- and NK-cell neoplasms, the most relevant updates concern to: 1-dysregulation of the JAK/STAT pathway due to gene mutations which are common to various aggressive and indolent neoplasms; 2-incorporation of new molecular players that are relevant to the pathogenesis of these neoplasms and/or have prognostic implications; 3-inclusion of new provisional entities within the subgroups of anaplastic, primarily intestinal and cutaneous lymphomas such as breast implant-associated anaplastic large cell lymphoma, indolent T-cell lymphoproliferative disorder of the gastrointestinal tract and primary cutaneous acral CD8+ T-cell lymphoma; 4-identification of poor prognostic subtypes of peripheral T-cell lymphomas not otherwise specified (PTCL, NOS) characterized by overexpression of certain genes and of a subgroup PTCL, NOS with a T follicular phenotype that now is included together with angioimmunoblastic T-cell lymphoma under the umbrella of lymphomas with a T follicular helper phenotype; and 5-refinement on the designation and definition of already established entities. A review of the major changes will be outlined.

Reexamining post-transplant lymphoproliferative disorders: Newly recognized and enigmatic types.

Post-transplant lymphoproliferative disorders (PTLD) are a known risk for both solid organ transplant and stem cell transplant recipients. Overall transplant recipients have a six fold increase in risk for developing any kind of non-Hodgkin lymphoma and PTLDs occur in up to 10% of SOT recipients. Several new entities have been accepted or renamed in the 2018 update of the WHO classification of tumors of hematopoietic and lymphoid neoplasms, including florid follicular hyperplasia and extranodal marginal zone lymphomas of mucosa-associated lymphoid tissue (MALT-lymphoma) (excluding common locations such as stomach and salivary gland). Other more rare types of PTLD have been reclassified including EBV-positive mucocutaneous ulcer, which is now a recognized diagnosis in its own right and should not be considered polymorphous PTLD. In this paper newly recognized PTLD entities and more unusual PTLDs will be examined.

Utility of CD200 expression and CD20 antibody binding capacity in differentiating chronic lymphocytic leukemia from other chronic lymphoproliferative disorders.

BACKGROUND: Chronic lymphoproliferative disorders (CLPDs) are heterogeneous group of disorders with variable clinical presentations and outcomes. Therefore, accurate classification is crucial for treatment planning. At present, flow cytometry immunophenotyping (FCM-IPT) is a useful tool for diagnosing these diseases. However, overlapping immunophenotypes do exist. Recently, differential expression of CD200 and variation in number of CD20 antibody bound per cell (ABC) in different CLPDs has been reported. MATERIALS AND METHODS: Seventy-seven CLPD cases were analyzed by FCM-IPT for CD200 expression, and Quantibrite bead was used to calculate CD20 ABC. RESULTS: Variability in CD200 expression can help in the differentiation of chronic lymphocytic leukemia (CLL) and hairy cell leukemia (HCL) from other CLPDs. CD200 was brightly expressed in 100% CLL cases, having homogenous bright (2+) intensity. On the contrary, CD200 was uniformly negative in all Mantle cell lymphoma cases except 1, in which the intensity was dim, and the mean fluorescence intensity was significantly lower than CLL. Furthermore, all HCL cases showed bright expression of CD200, thereby making it useful in differentiation from other CLPD with villous lymphocytes. Evaluation of CD20 ABC showed that it differs among various CLPD and was significantly lowest in CLL and highest in HCL both on peripheral blood and bone marrow samples. CONCLUSION: Our results support the fact that CD200 can be added to routine CLPD panel as it is useful in subcategorizing them. However, inclusion of CD20 ABC to routine panel does not seem plausible but may be done for difficult diagnostic cases or where anti-CD20 therapy is planned.

La revisión de 2016 de la clasificación de la OMS de las neoplasias linfoides: la visión del clínico / The 2016 revision of the WHO classification of lymphoid neoplasms: The clinician's view

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