Reassessment of small lymphocytic lymphoma in the era of monoclonal B-cell lymphocytosis

Indolent clonal lymphoid disorders

Indolent clonal lymphoid disorders are not recognized as lymphomas as they generally need no systemic treatment, and depending on the lesion, need only limited clinical follow-up. These lesions are usually incidentally diagnosed during the work up for other disease. The recognition of indolent clonal lymphoid disorders is important to avoid misdiagnosis as lymphoma and unnecessary treatment. Notwithstanding, some indolent disorders, especially B-cell disorders, may give important morbidity that is not related to disease burden but related to auto-immune disease which may need treatment. Further, some of these lesions may, at various rates, ultimately progress to lymphoma. As such, the indolent clonal lymphoid disorders also give an insight into the earliest stages of clonal lymphoid disease that may increase our understanding of lymphoma, although much needs yet to be elucidated. In this article both B- and T-cell indolent clonal lymphoid disorders are reviewed. Not included in this review are lymphoid lesions that may be mistaken for lymphoma, but are not clonal, such as indolent T-lymphoblastic proliferation or marginal zone hyperplasia with immunoglobulin light chain restriction. Further, an emphasis has been given to clonal lymphoid lesions and therefore indolent plasma cell lesions have not been included. Also excluded is indolent lymphoma that may not need treatment but nonetheless requires more regular follow up. One may rightfully argue that there may be a gray zone between what constitutes an indolent clonal lymphoid disorder and an indolent lymphoma. This discussion is reflected in the different terminology used for some entities between editions of the WHO classification and between the Fifth Edition of the WHO Classification and the International Consensus Classification (ICC). The former has been used as a selection basis for this review, but cross-reference has been made to the ICC nomenclature when that differs as well as to the earlier Revised Fourth Edition of the WHO Classification (WHO-r4). For this reason, indolent T-cell lymphoma of the gastrointestinal tract (ICC: indolent clonal T-cell lymphoproliferative disorder of the gastrointestinal tract) is not included in this review.

Are small lymphocytic lymphoma and chronic lymphocytic leukemia the same disease? The unsolved dilemma

The management of small lymphocytic lymphoma (SLL) as chronic lymphocytic leukemia (CLL) or an indolent non-Hodgkin lymphoma is highly debated. In this single-center, real-life study, 38 SLL patients managed between 2008 and 2022 were evaluated. Overall, 26/38 cases (68.4%) needed treatment and all but one received CLL concordant therapy, including BR (9/38 cases), fludarabine, cyclophosphamide, rituximab (5/38 cases), rituximab and chlorambucil (4/38 cases), BTK inhibitors (7/38 cases) and steroid (1 case with immune thrombocytopenia). Patients treated between 2008 and 2018 were more likely to receive chemoimmunotherapy compared to patients treated in 2019-2022, that were more likely to receive BTK inhibitors. The median PFS was 54 months and 3-y PFS was 58%, while the median OS was not reached, with a 3-y OS of 84%. We confirm a wide heterogeneity in SLL management and we suggest prospective studies are needed to improve the knowledge of its biology and harmonize its treatment.

Fifth Edition of the World Health Classification of Tumors of the Hematopoietic and Lymphoid Tissues: B-cell Neoplasms

We review B-cell neoplasms in the 5th edition of the World Health Organization classification of hematolymphoid tumors (WHO-HEM5). The revised classification is based on a multidisciplinary approach including input from pathologists, clinicians, and other experts. The WHO-HEM5 follows a hierarchical structure allowing the use of family (class)-level definitions when defining diagnostic criteria are partially met or a complete investigational workup is not possible. Disease types and subtypes have expanded compared with the WHO revised 4th edition (WHO-HEM4R), mainly because of the expansion in genomic knowledge of these diseases. In this review, we focus on highlighting changes and updates in the classification of B-cell lymphomas, providing a comparison with WHO-HEM4R, and offering guidance on how the new classification can be applied to the diagnosis of B-cell lymphomas in routine practice.

Chronic lymphocytic leukaemia/small lymphocytic lymphoma and mantle cell lymphoma: from early lesions to transformation

The International Clinical Advisory Committee reviewed advances in our understanding of the clinicopathologic and biologic features of chronic lymphocytic leukaemia/small lymphocytic lymphoma, B-cell prolymphocytic leukaemia, and mantle cell lymphoma since the revised 4th edition of the WHO Classification of Tumours of the Haematopoietic and Lymphoid Tissues. Discussions amongst pathologists, clinicians, and molecular geneticists around these diseases focussed on incorporating new knowledge into the next classification system. In this manuscript, we review these disease entities and incorporate results of these deliberations, including advances in our understanding of early lesions and transformation.

The International Consensus Classification of Mature Lymphoid Neoplasms: a report from the Clinical Advisory Committee

Since the publication of the Revised European-American Classification of Lymphoid Neoplasms in 1994, subsequent updates of the classification of lymphoid neoplasms have been generated through iterative international efforts to achieve broad consensus among hematopathologists, geneticists, molecular scientists, and clinicians. Significant progress has recently been made in the characterization of malignancies of the immune system, with many new insights provided by genomic studies. They have led to this proposal. We have followed the same process that was successfully used for the third and fourth editions of the World Health Organization Classification of Hematologic Neoplasms. The definition, recommended studies, and criteria for the diagnosis of many entities have been extensively refined. Some categories considered provisional have now been upgraded to definite entities. Terminology for some diseases has been revised to adapt nomenclature to the current knowledge of their biology, but these modifications have been restricted to well-justified situations. Major findings from recent genomic studies have impacted the conceptual framework and diagnostic criteria for many disease entities. These changes will have an impact on optimal clinical management. The conclusions of this work are summarized in this report as the proposed International Consensus Classification of mature lymphoid, histiocytic, and dendritic cell tumors.

Prescription of Blood Lymphocyte Immunophenotyping in the Diagnosis of Lymphoid Neoplasms in Older Adults

Lymphoid neoplasms are a heterogeneous group of lymphoid neoplastic diseases with multiple presentations, and varying prognoses. They are especially frequent in older patients (OPs) and the atypism of this frail elderly population can make the diagnostic process even more difficult. Blood lymphocyte immunophenotyping (BLI) is essential in rapid noninvasive diagnosis orientation and guides complementary investigations. To our knowledge, BLI prescription has never been evaluated in OPs. We hypothesized that, when there is a suspicion of lymphoid neoplasm in the geriatric population, a BLI is performed in view of various clinical or biological abnormalities. This study aimed to: (1) describe the characteristics of hospitalized OPs having undergone BLI for suspected lymphoid neoplasm, (2) identify the causes leading to BLI prescription, and (3) identify the most profitable criteria for BLI prescription. This was a descriptive retrospective study on 151 OPs aged ≥75 years who underwent BLI over a 2-year period. Regarding BLI prescriptions, eight had lymphocytosis, constituting the “lymphocytosis group” (LG+), while the 143 others had BLI prescribed for reasons other than lymphocytosis (LG−), mainly general weakness and anemia. In the LG−, we compared OPs with positive and negative BLI results. The criteria found to be profitable for BLI prescription were lymphadenopathy, splenomegaly, lymphocytosis, and thrombocytopenia. BLI identified circulating lymphoid neoplasms (positive BLI) in 21/151 OPs, mainly marginal zone lymphoma and chronic lymphocytic leukemia. In polymorbid OPs, as per our study population, the diagnostic and therapeutic complexity explained in part the sole use of indirect and minimally invasive diagnostic techniques such as BLI.

Clinicopathologic Findings in Patients With Initial Diagnosis of Extranodal Marginal Zone B-Cell Lymphoma of Mucosa-Associated Lymphoid Tissue (MALT) in Colorectal Mucosa

OBJECTIVES

To evaluate clinicopathologic features, management, and behavior of colorectal extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT).

METHODS

Clinical data, laboratory studies, and radiographic records were reviewed (2005-2018), and fluorescence in situ hybridization studies were performed.

RESULTS

Eleven patients were identified, six of whom were discovered as an incidental finding on endoscopy. Morphologic and immunophenotypic features were similar to MALT lymphomas at other sites except that lymphoepithelial lesions were uncommon. Three of nine patients were positive for BIRC3/MALT1 fusions, two of whom had identical B-cell clones identified in subsequent gastric biopsy specimens. Eight of 10 patients had no clinically evaluable disease after observation (±antibiotics; n = 4) or radiation/chemotherapy (n = 4).

CONCLUSIONS

Patients with incidental and localized colonic MALT lymphoma demonstrated an excellent prognosis with conservative management, although longer follow-up and data based on consistent staging and surveillance methods (including gastric evaluation) are necessary for informed management.

How to Diagnose and Treat CD5-Positive Lymphomas Involving the Spleen

Patients with CD5-expressing lymphomas presenting with splenomegaly are frequently diagnosed with chronic lymphocytic leukemia. The most important differential diagnosis is mantle cell lymphoma, both in its classical and leukemic, non-nodal forms, given its prognostic and therapeutic implications. Other small B-cell neoplasms that frequently involve the spleen and occasionally express CD5 include the splenic marginal zone lymphoma, hairy cell leukemia and, rarely, lymphoplasmacytic lymphoma. The frequency of CD5 positivity depends in part on the sensitivity of the detection methods employed. Usually, a combination of morphological, immunophenotypic and molecular findings allows for a precise sub-classification of CD5-positive, low-grade B-cell lymphomas of the spleen. Some of these tumors may display a mixture of small and larger B cells, raising the possibility of more aggressive lymphomas, such as diffuse large B-cell lymphomas (DLBCL). Approximately 5-10% of DLBCL are CD5-positive and some may manifest as primary splenic lesions. When available, the morphology of DLBCL in the splenic tissue is distinctive and a leukemic picture is very rare. In conclusion, the appropriate morphological and clinical context assisted by flow cytometry panels and/or immunohistochemistry allows the differential diagnosis of CD5-positive, non-Hodgkin, B-cell lymphomas involving the spleen.

A Tissue Counterpart to Monoclonal B-Cell Lymphocytosis

CONTEXT.—

B-cell clones discovered in tissue biopsies, without overt lymphoma, may represent a tissue counterpart to peripheral blood monoclonal B-cell lymphocytosis (MBL), herein termed tMBL.

OBJECTIVE.—

To characterize the clinicopathologic features of tMBL.

DESIGN.—

During a 10-year period, we retrospectively identified non-bone marrow/peripheral blood cases with monotypic B cells detected by tissue-based flow cytometry, but without an identifiable lymphomatous infiltrate on routine histopathology. We excluded cases with prior diagnosis of chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma or MBL.

RESULTS.—

Fifty-four cases were identified (35 lymph node, 3 splenic, and 16 soft tissue/viscera). Forty-six cases were CLL-type, 2 were atypical CLL, and 6 were non-CLL. tMBL was detectable by immunohistochemistry in 14 cases (26%, all CLL-type). Concurrent blood flow cytometry, available in 10 cases, showed 4 with low-count MBL (3 CLL-type, 1 with non-CLL-type), 5 with high-count MBL (all CLL-type), and 1 case negative for clonal population. With median follow-up of 51 months, 2 patients had progression of disease (CLL, 68.7 months; and diffuse large B-cell lymphoma, 5.9 months). Patients with IHC-detectable tMBL had increased monoclonal B cells per total lymphocyte events (P = .01), morphologic evidence of bone marrow involvement (P = .04), higher white blood cell count (P = .02), and increased absolute lymphocyte count (P = .02).

CONCLUSIONS.—

tMBL spans an immunophenotypic spectrum similar to MBL, is detectable by immunohistochemistry in a minority of cases (often CLL immunophenotype), and is likely systemic in most cases. Development of overt lymphoma is uncommon but may occur, warranting clinical follow-up.

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.

Scientific Advances and the Evolution of Diagnosis, Subclassification and Treatment of Lymphoma

The diagnosis of lymphoma has evolved tremendously over time. Initially, diagnosis of lymphoma was largely based on morphology alone. Over time, immunophenotyping using flow cytometry and immunohistochemistry, and then in situ hybridization, have contributed dramatically to the pathologist's ability to recognize, diagnose and subclassify lymphomas more precisely. In recent years, cytogenetic and molecular genetic techniques have developed that allow evaluation of abnormalities in lymphomas, leading to an understanding of their pathogenesis and opening the door to targeted therapies that will lead to better outcomes for lymphoma patients.

Erdheim-Chester Disease and Small Lymphocytic Lymphoma Collision Tumour Presenting as a Perirenal Mass

Background

Erdheim-Chester disease is a rare histiocytic neoplasm associated with MAPK pathway mutations. Disease manifestation is variable often involving many different organs, mainly bone, retroperitoneum, the heart, and the central nervous system. Histological findings include foamy histiocytes in a fibrous stroma with scattered inflammatory infiltrate. Histiocytes are CD68 positive and S100 negative. Case Report. We report a case of Erdheim-Chester disease associated with small lymphocytic lymphoma presenting as a perirenal mass with a review of the recent literature.

Conclusions

Erdheim-Chester disease rarely can be associated with other cancers, namely myeloid neoplasms. We report a case of Erdheim-Chester disease presenting with small lymphocytic lymphoma as a perirenal mass. The association of Erdheim-Chester disease with lymphoproliferative disorders needs to be elucidated.

Early Events in Lymphoid Neoplasms and Indolent Follicular Lymphomas

Technical advances in diagnostic modalities have led to the characterization of indolent lymphoid disorders similar to the in situ lesions described in epithelial malignancies. These early and indolent lymphoid lesions share clinicopathologic characteristics with well-characterized lymphoid malignancies such as chronic lymphocytic leukemia and follicular lymphoma. The in situ lesions have an indolent clinical course with only a minor subset shown to progress to frank malignancies. In addition to the in situ lesions, new indolent lymphoproliferative disorders have been recently characterized. Diagnosis and characterization of these indolent lesions is necessary to prevent overtreatment with aggressive therapeutic regimens.

[Revised version of the 4th edition of the WHO classification of malignant lymphomas : What is new?]

After 8 years, the WHO has now published the updated version of the 4th edition of the classification of hematopoietic and lymphoid tumors. This update provides a conceptual rewrite of existing entities as well as some new provisional entities and categories, particularly among the aggressive B‑cell lymphomas. Important new diagnostic categories include the high-grade B‑cell lymphomas, the large B‑cell lymphoma with IRF4 rearrangement, and the Burkitt-like lymphoma with 11q aberrations. Of particular importance, new concepts concerning the taxonomy and classification of early lymphoid lesions or precursor lesions are included, such as the in situ follicular neoplasia or the in situ mantle cell neoplasia. In addition, the concept of indolent lymphoproliferations, such as breast-implant-associated anaplastic large cell lymphoma and the indolent T‑cell lymphoproliferative disorder of the gastrointestinal tract, has been strengthened. Finally, diagnostic criteria for existing lymphoma entities have been refined.

Premalignant Clonal Hematopoietic Proliferations

OBJECTIVES

The 2017 Workshop of the Society for Hematopathology/European Association for Hematopathology aimed to review premalignant clonal hematopoietic proliferations.

METHODS

The workshop panel reviewed 27 cases of clonal proliferations of indeterminate significance or potential (18 myeloid, nine lymphoid) and rendered consensus diagnoses.

RESULTS

Immunophenotyping and genetic studies on peripheral blood, bone marrow, and lymph node samples have led to the incidental detection of small clonal populations in asymptomatic individuals. These premalignant clonal myeloid and lymphoid proliferations include monoclonal gammopathy of uncertain significance, monoclonal B-cell lymphocytosis, in situ follicular neoplasia, in situ mantle cell neoplasia, clonal hematopoiesis of indeterminate potential, and clonal cytopenia of undetermined significance.

CONCLUSIONS

Current diagnostic criteria for the diagnoses of premalignant clonal hematopoietic proliferations are reviewed and discussed in the context of the cases presented at the workshop.

Composite Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma and T-Prolymphocytic Leukemia Presenting with Lymphocytosis, Skin Lesions, and Generalized Lymphadenopathy

Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in Western countries with an incidence of 3-5 cases per 100,000 persons. Most patients follow an indolent clinical course with eventual progression and need for therapy. In contrast, T-prolymphocytic leukemia (T-PLL) is a rare type of T-cell leukemia with most patients having an aggressive clinical course and a dismal prognosis. Therapies are limited for T-PLL patients and there is a high relapse rate. Morphologically, the cells of CLL and T-PLL can show overlapping features. Here, we report the case of a 61-year-old man who presented with a clinically indolent CLL and T-PLL, initially diagnosed solely and followed as CLL, despite the presence of an associated but unrecognized aberrant T-cell population in blood. After 2 years, the T-PLL component became more apparent with cutaneous and hematologic manifestations and the diagnosis was confirmed by immunophenotypic and cytogenetic analysis. Fluorescence in situ hybridization demonstrated an ATM deletion in both CLL and T-PLL components. Retrospective testing demonstrated that composite CLL and T-PLL were both present in skin and lymph nodes as well as in blood and bone marrow since initial presentation. This case is also unique because it highlights that a subset of T-PLL patients can present with clinically indolent disease. The concomitant detection of ATM mutation in CLL and T-PLL components raises the possibility of a common pathogenic mechanism.

The frequency of NOTCH1 variants in T-acute lymphoblastic leukemia/lymphoma and chronic lymphocytic leukemia/small lymphocytic lymphoma among Jordanian patients

The transmembrane receptor NOTCH1 is thought to be associated with the development and progression of T-acute lymphoblastic leukemia (T-ALL)/T-lymphoblastic lymphoma (T-LBL) and chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). The current study aimed to characterize NOTCH1 expression and elucidate the variants in the functional PEST domain of the receptor in T-ALL/LBL and CLL/SLL. The nuclear expression of NOTCH1 protein was detected in 25% and 5% of cases of T-ALL/LBL and CLL/SLL, respectively, whereas cytoplasmic expression was detected in 33.3% and 15% cases, respectively. The frequency of variants in T-ALL/LBL was 33%, whereas 40% of CLL/SLL cases possessed variants. Four novel variants were identified; three of which were non-synonymous and one common variant c.7280_7280delG between T-ALL/LBL and CLL/SLL cases. The previously described variant, c.7541_7542delCT, was detected in 3 cases of CLL/SLL. These results provide support for the contribution of NOTCH1 in the etiology of these types of cancers.

The current role of clinical flow cytometry in the evaluation of mature B-cell neoplasms

Flow cytometry (FC) has a well-established role in the diagnostic evaluation of mature B-cell neoplasms. Effective assessment for lineage associated antigens, aberrant antigen expression, and immunoglobulin light chain restriction requires a well-designed, optimized, and controlled FC assay. However, it is important for hematopathologists to know when flow cytometry has a more limited role, and other modalities, such as immunohistochemistry, cytogenetic and molecular testing, are more important. This review will discuss the features of an optimal FC assay for the evaluation of mature B-cell neoplasms, and the current role of FC in the diagnosis and sub-classification, prognostic assessment, identification of therapeutic targets, and assessment for disease response to therapy. © 2018 International Clinical Cytometry Society.

Diagnostically relevant updates to the 2017 WHO classification of lymphoid neoplasms

The recent 2017 WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues contains a number of updates under the category of lymphoid neoplasms. These changes include introduction of new entities, amended classification or terminology, and addition of newly discovered diagnostic and molecular features. In this review, we perform a focused, concise summary of selected lymphoid neoplasms and discuss changes in their classification. Rather than a comprehensive overview, we place specific emphasis on important and diagnostically relevant aspects of each entity that are novel or different from the previous WHO iteration and bring the practicing pathologist quickly up to speed with the updated classification.

Clinical Impact of the 2016 Update to the WHO Lymphoma Classification

OPINION STATEMENT

The 2016 revision of the WHO classification of lymphoid neoplasms includes new entities along with a clearer definition of provisional and definitive subtypes based on better understanding of the molecular drivers of lymphomas. These changes impact current treatment paradigms and provide a framework for future clinical trials. Additionally, this update recognizes several premalignant or predominantly indolent entities and underscores the importance of avoiding unnecessarily aggressive treatment in the latter subsets.

Guidelines for Diagnosis and Treatment of Chronic Lymphocytic Leukemia. Krohem B-Cll 2017

Recent developments in the diagnosis and treatment of chronic lymphocytic leukemia (B-CLL) have led to change of approach in clinical practice. New treatments have been approved based on the results of randomized multicenter trials for first line and for salvage therapy, and the results of numerous ongoing clinical trials are permanently providing new answers and further refining of therapeutic strategies. This is paralleled by substantial increase in understanding the disease genetics due to major advances in the next generation sequencing (NGS) technology. We define current position of the Croatian Cooperative Group for Hematologic Disease on diagnosis and treatment of CLL in the transition from chemo-immunotherapy paradigm into a new one that is based on new diagnostic stratification and unprecedented therapeutic results of B-cell receptor inhibitors (BRI) and Bcl-2 antagonists. This is a rapidly evolving field as a great number of ongoing clinical trials con-stantly accumulate and provide new knowledge. We believe that novel therapy research including genomic diagnosis is likely to offer new options that will eventually lead to time limited therapies without chemotherapy and more effective clinical care for B-CLL based on individualized precision medicine.

The mutational landscape of small lymphocytic lymphoma compared to non-early stage chronic lymphocytic leukemia

Small lymphocytic lymphoma (SLL) is considered as the non-leukemic form of presentation of chronic lymphocytic leukemia (CLL). We have compared the features, genomic alterations, and outcome of 890 patients with CLL and SLL. One hundred and thirteen patients presented as SLL and more frequently had unmutated-IGHV, CD38^high, ZAP-70^high, CD49d^high, +12, alterations in genes of NOTCH1, cell cycle, RNA metabolism, and NFkB pathways than CLL. During the follow-up, 46% of SLL patients developed CLL. Time to first treatment (TTFT) was shorter in SLL (10-year: 75% vs 62%; p = .006). Binet stage, SLL, and IGHV were independent predictive factors for TTFT. Transformation to diffuse large B-cell lymphoma was higher (10-year: 12% vs 6%; p = .003), and overall survival was shorter in SLL (10-year: 55% vs 66%; p = .004). When A0 CLL patients were excluded, only CD38 and CD49d expression, +12, and 10-year TTFT remained different between the SLL and CLL patients. In summary, SLL showed only minor clinicobiological differences when compared with CLL in similar clinical stages.

Practical Implications of the 2016 Revision of the World Health Organization Classification of Lymphoid and Myeloid Neoplasms and Acute Leukemia

A major revision of the WHO classification of lymphoid and myeloid neoplasms and acute leukemia was released in 2016. A key motivation for this update was to include new information available since the 2008 version with clinical relevance for the diagnosis, prognosis, and therapy of patients. With > 100 entities described, it is important for the clinician to understand features that may be important in daily practice, whereas researchers need to incorporate the new classification scheme into study development and analysis. In this review, we highlight the key aspects of the 2016 update with particular importance to routine patient care and clinical trial design.

CD49d shows superior performance characteristics for flow cytometric prognostic testing in chronic lymphocytic leukemia/small lymphocytic lymphoma

BACKGROUND

CD49d is emerging as a powerful adverse prognostic marker in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). However, flow cytometric testing for CD49d has not yet been widely adopted in the United States, in part due to the lack of establishment of its performance characteristics in the clinical setting, especially in comparison with the more common CLL/SLL prognostic markers CD38 and ZAP-70.

METHODS

CD49d expression levels in 124 CLL/SLL cases were assessed among peripheral blood (PB), bone marrow (BM), and lymph node (LN) specimens and correlated with available CD38 and ZAP-70 expression and cytogenetic findings. For 10 PB/BM specimens, the stability of CD49d, CD38, and ZAP-70 expression was assessed at <24 hours, 48 hours, 72 hours, and 96 hours.

RESULTS

39% (28 of 71) PB, 56% (18 of 32) BM, and 71% (15 of 21) LN involved by CLL/SLL were CD49d+, using a ≥30% threshold. The mean for the CD49d+ cases was 2.8 standard deviations (SD) above the cutoff for positivity, compared with 1.7 SD for CD38 and 1.1 SD for ZAP-70. CD49d demonstrated the lowest mean SD (0.91) and coefficient of variation (CV) (8.0%) compared with CD38 (SD = 2.1, CV = 10.4%) and ZAP-70 (SD = 9.8, CV = 40.5%) in stability studies over a 96-hours time period. CD49d+ CLL/SLL correlated with trisomy 12 (P = 0.025) and lack of isolated deletion (13q) (P = 0.005). CD38+ CLL/SLL correlated with deletion (11q) (P = 0.025). ZAP-70 did not correlate with any underlying cytogenetic abnormality.

CONCLUSIONS

CD49d is a robust adverse prognostic marker in CLL/SLL with superior performance characteristics. © 2016 International Clinical Cytometry Society.

Issues in diagnosis of small B cell lymphoid neoplasms involving the bone marrow and peripheral blood. Report on the Bone Marrow Workshop of the XVIIth meeting of the European Association for Haematopathology and the Society for Hematopathology

Small B cell lymphoid neoplasms are the most common lymphoproliferative disorders involving peripheral blood (PB) and bone marrow (BM). The Bone Marrow Workshop (BMW) organized by the European Bone Marrow Working Group (EBMWG) of the European Association for Haematopathology (EAHP) during the XVIIth EAHP Meeting in Istanbul, October 2014, was dedicated to discussion of cases illustrating how the recent advances in immunophenotyping, molecular techniques and cytogenetics provide better understanding and classification of these entities. Submitted cases were grouped into following categories: (i) cases illustrating diagnostic difficulties in chronic lymphocytic leukaemia (CLL); (ii) cases of BM manifestations of small B cell lymphoid neoplasms other than CLL; (iii) transformation of small B cell lymphoid neoplasms in the BM; and (iv) multiclonality and composite lymphomas in the BM. This report summarizes presented cases and conclusions of the BMW and provides practical recommendations for classification of the BM manifestations of small B cell lymphoid neoplasms based on the current state of knowledge.

The 2016 revision of the World Health Organization classification of lymphoid neoplasms

A revision of the nearly 8-year-old World Health Organization classification of the lymphoid neoplasms and the accompanying monograph is being published. It reflects a consensus among hematopathologists, geneticists, and clinicians regarding both updates to current entities as well as the addition of a limited number of new provisional entities. The revision clarifies the diagnosis and management of lesions at the very early stages of lymphomagenesis, refines the diagnostic criteria for some entities, details the expanding genetic/molecular landscape of numerous lymphoid neoplasms and their clinical correlates, and refers to investigations leading to more targeted therapeutic strategies. The major changes are reviewed with an emphasis on the most important advances in our understanding that impact our diagnostic approach, clinical expectations, and therapeutic strategies for the lymphoid neoplasms.

Premalignant cell dynamics in indolent B-cell malignancies

PURPOSE OF REVIEW

Follicular lymphoma and chronic lymphocytic leukemia (CLL) are indolent B-cell malignancies characterized by a long preclinical phase and frequent relapses once treatment is initiated. The present review gathers recent findings on the occurrence, relevance, and dynamics of premalignant cells in the development of follicular lymphoma and CLL.

RECENT FINDINGS

The frequency of circulating cells bearing the follicular lymphoma hallmark translocation t(14;18) in healthy persons is correlated to the risk of developing follicular lymphoma later in life. Chronic B-cell receptor stimulation induces cyclic re-entries of BCL2 B cells into germinal centers that propagate clonal evolution and early follicular lymphoma progression. The lymph node microenvironment is a key activation/proliferation niche for malignant cells in CLL, also active in its preclinical antecedent monoclonal B-cell lymphocytosis.

SUMMARY

Considering recent studies of premalignant cells in both diseases and of their putative normal cell counterparts, we propose different models of premalignant evolution for the two pathologies. Before overt follicular lymphoma, t(14;18) B cells exploit the dynamics of memory B cells to re-enter multiple times into local or distant germinal centers, gather activation/proliferation signals, and gain additional mutations to progress to malignant lymphoma. In monoclonal B-cell lymphocytosis, CLL-like activated/memory B cells follow cycles of germinal center-independent activation/proliferation in lymph node. Finally, we discuss the next level genetic and functional analyses that should result in a better understanding of the origins and mechanisms of frequent relapses in follicular lymphoma and CLL.

What does it mean I have a monoclonal B-cell lymphocytosis?: Recent insights and new challenges

Monoclonal B-cell lymphocytosis (MBL) is defined as a laboratory abnormality where small (<5 x 10(9)/L) clonal B-cell populations are detected in the peripheral blood of otherwise healthy subjects. According to the immunophenotype, MBL is labeled as chronic lymphocytic leukemia (CLL)-like (75% of cases), atypical CLL, and CD5-negative. Concentration of clonal B cells differentiates low- (LC) and high-count (HC)-MBL (< or ≥ 0.5 x 10(9)/L, respectively). Thanks to technical improvements, we are able to identify CLL-like clonal B-cell populations at increased frequency with age, but we are still far from understanding its relationship with clinically overt CLL. LC-MBL, requiring high-throughput screening technique to be identified in population studies, seems to be a bird of a different feather and several hints suggest that LC-MBL is related to aging and/or chronic antigenic stimulation. Immunogenetic, cytogenetic and genetic data support the notion that HC-MBL, usually identified in the clinical setting, is a premalignant condition and, based on biological parameters, it is frequently difficult to differentiate it from early stage CLL. The rapid improvement and widespread availability of cutting-edge technology, in particular next-generation sequencing (NGS), raises hope that we are getting closer to unveiling the fundamental nature of MBL and CLL and how they are related to each other.

Lymphocytosis, lymphadenopathy: benign or malignant?

The increasing use of immunophenotypic and molecular analysis in the routine evaluation of patients with lymphocytosis, lymphadenopathy, or other hematologic disorders has led to the identification of unexpected small clonal lymphoid populations. These clones, sometimes with disease-specific markers, such as the t(14;18), are especially challenging for the clinician because of their unknown biologic potential and uncertain clinical behavior. Study of these early lymphoid lesions is providing important clues to the process of lymphomagenesis, and may provide the rationale for preemptive therapy in the future. More and more, the hematologist/oncologist is consulted regarding otherwise healthy individuals with lymphadenopathy and/or lymphocytosis, and pathology reports that confound the referring internist or surgeon. The report does not name a malignant lymphoproliferative disorder, but is not completely “normal”. Does the patient have a benign or malignant condition? How should they be evaluated? Is treatment indicated? These patients prove challenging for the consulting hematologist as well as the referring physician. In this review, we will focus on some of these scenarios and attempt to provide guidance for their management.

The many faces of small B cell lymphomas with plasmacytic differentiation and the contribution of MYD88 testing

Plasmacytic differentiation may occur in almost all small B cell lymphomas (SBLs), although it varies from being uniformly present (as in lymphoplasmacytic lymphoma (LPL)) to very uncommon (as in mantle cell lymphomas (MCLs)). The discovery of MYD88 L265P mutations in the vast majority of LPLs has had a major impact on the study of these lymphomas. Review of the cases contributed to the 2014 European Association for Haematopathology/Society for Hematopathology slide workshop illustrated how mutational testing has helped refine the diagnostic criteria for LPL, emphasizing the importance of identifying a clonal monotonous lymphoplasmacytic population and highlighting how LPL can still be diagnosed with extensive nodal architectural effacement, very subtle plasmacytic differentiation, follicular colonization, or uncommon phenotypes such as CD5 or CD10 expression. MYD88 L265P mutations were found in 11/11 LPL cases versus only 2 of 28 other SBLs included in its differential diagnosis. Mutational testing also helped to exclude other cases that would have been considered LPL in the past. The workshop also highlighted how plasmacytic differentiation can occur in chronic lymphocytic leukemia/small lymphocytic lymphoma, follicular lymphoma, SOX11 negative MCL, and particularly in marginal zone lymphomas, all of which can cause diagnostic confusion with LPL. The cases also highlighted the difficulty in distinguishing lymphomas with marked plasmacytic differentiation from plasma cell neoplasms. Some SBLs with plasmacytic differentiation can be associated with amyloid, other immunoglobulin deposition, or crystal-storing histiocytosis, which may obscure the underlying neoplasm. Finally, although generally indolent, LPL may transform, with the workshop cases suggesting a role for TP53 abnormalities.

Monoclonal B-cell lymphocytosis and early-stage chronic lymphocytic leukemia: diagnosis, natural history, and risk stratification

Monoclonal B lymphocytosis (MBL) is defined as the presence of a clonal B-cell population in the peripheral blood with fewer than 5 × 10(9)/L B-cells and no other signs of a lymphoproliferative disorder. The majority of cases of MBL have the immunophenotype of chronic lymphocytic leukemia (CLL). MBL can be categorized as either low count or high count based on whether the B-cell count is above or below 0.5 × 10(9)/L. Low-count MBL can be detected in ∼5% of adults over the age of 40 years when assessed using standard-sensitivity flow cytometry assays. A number of biological and genetic characteristics distinguish low-count from high-count MBL. Whereas low-count MBL rarely progresses to CLL, high-count MBL progresses to CLL requiring therapy at a rate of 1% to 2% per year. High-count MBL is distinguished from Rai 0 CLL based on whether the B-cell count is above or below 5 × 10(9)/L. Although individuals with both high-count MBL and CLL Rai stage 0 are at increased risk of infections and second cancers, the risk of progression requiring treatment and the potential to shorten life expectancy are greater for CLL. This review highlights challenging questions regarding the classification, risk stratification, management, and supportive care of patients with MBL and CLL.

Chronic lymphocytic leukemia/small lymphocytic lymphoma: another neoplasm related to the B-cell follicle?

Although there has been increased attention paid to the critical nature of nodal involvement in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), the B-cell compartment it is most closely related to and its relationship to the follicle remain uncertain. A clinicopathologic investigation of 60 extramedullary biopsies of LEF1+ CLL/SLL, including 29 cases with perifollicular/follicular (PF/F) growth, was therefore performed. A subset of PF/F cases demonstrated inner mantle zone preservation or intra-mantle zone growth. All PF/F and 16/31 other cases contained CD21+ follicular dendritic cells. No cytogenetic, IGHV mutational or gene usage differences were seen between PF/F and diffuse cases. PF/F cases were more often kappa positive (p<0.03) and had fewer involved nodal sites (p=0.0004). These findings suggest that at least a subset of bona fide CLL/SLL is related to the follicle, most likely the outer mantle zone, and that at least a subset of the diffuse cases may represent "later" disease.

Early lymphoid lesions: conceptual, diagnostic and clinical challenges

There are no "benign lymphomas", a fact due to the nature of lymphoid cells to circulate and home as part of their normal function. Thus, benign clonal expansions of lymphocytes are only rarely recognized when localized. Recent studies have identified a number of lymphoid proliferations that lie at the interface between benign and malignant. Some of these are clonal proliferations that carry many of the molecular hallmarks of their malignant counterparts, such as BCL2/IGH and CCND1/IGH translocations associated with the in situ forms of follicular lymphoma and mantle cell lymphoma, respectively. There are other clonal B-cell proliferations with low risk of progression; these include the pediatric variants of follicular lymphoma and marginal zone lymphoma. Historically, early or incipient forms of T/NK-cell neoplasia also have been identified, such as lymphomatoid papulosis and refractory celiac disease. More recently an indolent form of T-cell lymphoproliferative disease affecting the gastrointestinal tract has been described. Usually, CD8(+), the clonal cells are confined to the mucosa. The clinical course is chronic, but non-progressive. NK-cell enteropathy is a clinically similar condition, composed of cytologically atypical NK-cells that may involve the stomach, small bowel or colon. Breast implant-associated anaplastic large cell lymphoma is a cytologically alarming lesion that is self-limited if confined to the seroma cavity. Atypical lymphoid proliferations that lie at the border of benign and malignant can serve as instructive models of lymphomagenesis. It is also critical that they be correctly diagnosed to avoid unnecessary and potentially harmful therapy.

Primary gallbladder small lymphocytic lymphoma as a rare postcholecystectomy finding

Introduction. Primary lymphoma of the gallbladder is an extremely rare entity with approximately 50 cases reported so far. In many of these cases the presenting symptoms were mimicking symptomatic gallstone disease and the diagnosis was made postoperatively, especially when the preoperative imaging results were far from suspicious for malignant disease. Patients and Methods. We report a case of primary lymphoma of the gallbladder in an 85-year-old man with gallstone disease, who was admitted for elective cholecystectomy 2 months after an episode of acute cholecystitis and pancreatitis. Histological evaluation of the specimen revealed a small lymphocytic lymphoma of the gallbladder. This type of primary gallbladder lymphoma has not been previously reported. Discussion. The most common primary lymphomas of the gallbladder are MALT lymphomas and diffuse large B-cell lymphomas, although a variety of other histological types have been reported. The association of these lesions with chronic inflammation is the most convincing theory for their pathogenesis. For lesions confined to the gallbladder, cholecystectomy is considered to be sufficient, while supplementary chemotherapy significantly improves prognosis in more advanced disease.

Characterization of tissue findings in bone marrow biopsy specimens with small monoclonal B-cell populations

OBJECTIVES

Bone marrows (BMs) with incidentally identified, small monotypic B-cell populations (MBPs) were evaluated.

METHODS

BM aspirates with MBPs representing 5% or less of total events by flow cytometry, less than 5.0 × 10(9)/L B cells in blood, and no history of lymphoma or MBP with a different phenotype from prior lymphoma were selected. Clinical, immunophenotypic, and histologic findings were evaluated.

RESULTS

Forty-one of 3,052 BMs had MBPs at 5% or less of total events (median, 1%); 17 were females and 24 were males aged 30 to 87 years (median, 73 years). The MBPs were CD5- in 24, CD5+ resembling chronic lymphocytic leukemia (CLL) in 13, and CD5+ unlike CLL in four. Eighteen of 40 had lymphoid aggregates (LAs) with mostly T cells or a mixture of B and T cells, but three cases had B-cell-rich LAs.

CONCLUSIONS

Unlike monoclonal B lymphocytosis in blood, MBPs in BMs were more commonly CD5-. Forty-five percent of BMs had LAs; none were interpreted as lymphoma, although three were suspicious for B-cell lymphoma.

Monoclonal B-cell lymphocytosis

Monoclonal B-cell lymphocytosis (MBL) is an asymptomatic hematologic condition defined by the presence of a small (<5 x 10(9)/L) clonal B-cell population in the peripheral blood in the absence of lymph-node enlargement, cytopenias or autoimmune diseases. It is found in approximately 3-12% of normal persons depending on the accuracy of analytical techniques applied. According to the immunophenotypic profile of clonal B-cells, the majority of MBL cases (75%) are classified as chronic lymphocytic leukemia (CLL)-like. This form may progress into CLL at a rate of 1-2% per year. It is thought that CLL is always preceded by MBL. The remaining MBL cases are defined as atypical CLL-like (CD5+/CD20(bright)) and CD5(-) MBL. The MBL clone size is quite heterogenous. Accordingly, two forms of MBL are identified: i) high-count, or 'clinical' MBL, in which an evidence of lymphocytosis (<5 x 10(9)/L clonal B-cells) is seen, and ii) a low-count MBL, in which a normal leukocyte count is found and that is identified only in population-screening studies. Both forms of MBL may carry the cytogenetic abnormalities that are the hallmark of CLL, including 13q-, 17p- and trisomy 12. Consistent with the indolent phenotype of this condition, genetic lesions, such as TP53, ATM, NOTCH1 and SF3B1 mutations, usually associated with high-risk CLL, are rarely seen. Overall, no prognostic indicator of evolution of MBL to overt CLL has been found at present time. However, taking into account this possibility, a clinical and lab monitoring (at least annually), is recommended.

Hepatitis C virus-related lymphoproliferative disorders encompass a broader clinical and morphological spectrum than previously recognized: a clinicopathological study

We describe a retrospective series of B-cell lymphoproliferative disorders associated with hepatitis C virus infection. In addition to splenic marginal zone lymphoma, follicular lymphoma and diffuse large B-cell lymphoma, all of which showed some specific features, we found two poorly described groups of cases. The first featured disseminated marginal zone lymphoma without splenic marginal zone lymphoma features, defying the current marginal zone lymphoma classification; the other consisted of monoclonal B lymphocytes in the peripheral blood, bone marrow or other tissues, with no clinical or histological evidence of lymphoma, and exhibiting a pattern that requires proper identification in order to avoid the misdiagnosis of the lymphoma. Diagnosis of hepatitis C virus infection-associated lymphoproliferative disorders requires the integration of clinical, pathological and molecular findings to establish an adequate diagnosis and decide the appropriate therapy to be applied.

MBL versus CLL: how important is the distinction?

Monoclonal B-cell lymphocytosis (MBL) is defined as a clonal B-cell expansion whereby the B-cell count is less than 5 × 10(9)/L and no symptoms or signs of lymphoproliferative disorders are detected. Based on B-cell count, MBL is further divided into low-count and clinical MBL. While low-count MBL seems to carry relevance mostly from an immunological perspective, clinical MBL and chronic lymphocytic leukemia appear to be overlapping entities. Only a deeper knowledge of molecular pathways and microenvironmental influences involved in disease evolution will help to solve the main clinical issue, i.e. how to differentiate nonprogressive and progressive cases requiring intensive follow-up.

Monoclonal B cell lymphocytosis and "in situ" lymphoma

The finding of monoclonal B-cell populations not fulfilling criteria for a lymphoid malignancy has given great impulse to study mechanisms involved in lymphomagenesis and factors responsible for the transition from B-cell precursor states to overt lymphoproliferative disorders. Monoclonal B cell expansions were initially recognized in peripheral blood of otherwise healthy subjects (thus defined monoclonal B-cell lymphocytosis, MBL) and in most cases share the immunophenotypic profile of chronic lymphocytic leukemia (CLL). The clinical relevance of this phenomenon is different according to B-cell count: high-count MBL is considered a preneoplastic condition and progresses to CLL requiring treatment at a rate of 1-2% per year, while low-count MBL, though persisting over time, has not shown a clinical correlation with frank leukemia so far. MBL other than CLL-like represent a minority of cases and are ill-defined entities for which clinical and biological information is still scanty. In situ follicular lymphoma (FL) and mantle cell lymphoma (MCL) are characterized by the localization of atypical lymphoid cells, carrying t(14;18)(q32;q21) or t(11;14)(q13;q32), only in the germinal centers and mantle zones respectively, where their normal counterparts are localized. The localization of these cells indicates that germinal centers or mantle zones provide appropriate microenvironments for cells carrying these oncogenic alterations to survive or proliferate. The progression of these lesions to overt lymphomas occurs rarely and may require the accumulation of additional genetic events. Individuals with these lymphoid proliferations should be managed with caution.