All patients with persistent polyclonal B cell lymphocytosis present Bcl-2/Ig gene rearrangements

Lymphoid aggregates in bone marrow: a diagnostic pitfall

Lymphoid aggregates in bone marrow specimens are a relatively frequent finding that may pose a diagnostic challenge for a pathologist. The distinction between reactive and neoplastic aggregates has significant clinical relevance. Although many testing modalities such as immunohistochemistry, flow cytometry and molecular studies are currently available in clinical laboratories, the appropriate utilisation of these modalities and the awareness of their potential pitfalls are important. When a neoplastic process is ruled out, the significance of benign lymphoid aggregates in bone marrow is often unclear, as they may be associated with a broad spectrum of conditions including infections, autoimmune disorders, medications, or may even be idiopathic.This review focuses on evidence-based criteria that can aid in making the distinction between benign and malignant lymphoid aggregates and discusses the advantages, disadvantages and limits of ancillary tests used for this purpose. Finally, the most common aetiologies of benign lymphoid aggregates and their associations with specific diseases are discussed.

B-cell signaling in persistent polyclonal B lymphocytosis (PPBL)

Persistent polyclonal B lymphocytosis (PPBL) is a benign hematological disorder characterized by a selective expansion of circulating polyclonal marginal zone (MZ)-like B cells. Previous reports demonstrated that cases of PPBL showed poor activation, proliferation and survival of B cells in vitro, yet the underlying defect remains unknown. Here we report for the first time an attenuated activation of the canonical NF-κB (nuclear factor of kappa light polypeptide gene enhancer in B cells) and mitogen-activated protein kinase/extracellular signal-regulated kinase pathway after CD40 stimulation. This defect was selective, as alternative NF-κB signaling after CD40 stimulation and both B-cell receptor- and Toll-like receptor 9-mediated activation remained unaffected. Reduced canonical NF-κB activation resulted in decreased IκBα and CD40 expression in resting cells. In PPBL patients, expression of Bcl-xL in MZ-like B cells did not increase upon activation, consistent with the high apoptosis rates of PPBL-derived B cells that were observed in vitro. The B-cell phenotype of mice with selective knockouts of early components of the CD40 signaling pathway resembles PPBL, but sequencing corresponding genes in sorted MZ-like B cells of PPBL patients did not reveal relevant genetic alterations. Nevertheless, the frequently observed mutations in early signaling components of the NF-κB pathway in MZ lymphomas underline the relevance of our findings for the pathogenesis of PPBL.

Lack of glucocorticoid-induced leucine zipper (GILZ) deregulates B-cell survival and results in B-cell lymphocytosis in mice

Glucocorticoids (GC) are widely used as antiinflammatory/immunosuppressive drugs and antitumor agents in several types of lymphoma and leukemia. Therapeutic doses of GC induce growth-suppressive and cytotoxic effects on various leukocytes including B cells. Molecular mechanisms of GC action include induction of GC target genes. Glucocorticoid-induced leucine zipper (GILZ) is a rapidly, potently, and invariably GC-induced gene. It mediates a number of GC effects, such as control of cell proliferation, differentiation, and apoptosis. Here we show that deletion of GILZ in mice leads to an accumulation of B lymphocytes in the bone marrow, blood, and lymphoid tissues. Gilz knockout (KO) mice develop a progressive nonlethal B lymphocytosis, with expansion of B220(+) cells in the bone marrow and in the periphery, dependent on increased B-cell survival. Decreased B-cell apoptosis in mice lacking GILZ correlates with increased NF-κB transcriptional activity and Bcl-2 expression. B cell-specific gilz KO mice confirmed that the effect of GILZ deletion is B-cell self-intrinsic. These results establish GILZ as an important regulator of B-cell survival and suggest that the deregulation of GILZ expression could be implicated in the pathogenesis of B-cell disorders.

[In situ lymphoma and other early stage malignant non-Hodgkin lymphomas]

The increasing use of immunohistochemical and molecular investigations of lymphatic tissues results in more frequent detection of early lymphoid proliferations. These show some but not all features of malignant lymphomas without fulfilling the diagnostic criteria for the diagnosis of lymphoid malignancy. In addition to well-known premalignant B-cell proliferations, such as monoclonal gammopathy of unknown significance (MGUS) and monoclonal B-cell lymphocytosis (MBL), so-called in situ lymphomas have recently been described with minimal infiltrates of clonal B-cells in morphologically reactive lymphoid tissues which show the phenotypic and genetic features of specific B-cell lymphoma subtypes and often show a characteristic topographical distribution. This article addresses a group of clonal lymphoproliferations with usually localized disease and excellent clinical prognosis, such as pediatric follicular lymphoma and nodal marginal zone lymphoma. Another group of early lesions not addressed in this review are virally induced lymphoproliferations which represent a grey zone between purely reactive lesions and malignant lymphomas and may pose significant diagnostic as well as clinical problems. In this review diagnostic criteria for early or in situ lesions and their distinction from partial infiltration by malignant lymphoma are described.

Histological and immunohistochemical features of the spleen in persistent polyclonal B-cell lymphocytosis closely mimic splenic B-cell lymphoma

Persistent polyclonal B-cell lymphocytosis (PPBL) is rare and intriguing hematological disorder predominantly reported in young to middle- aged smoking women. It is characterized by persistent moderate polyclonal B-cell lymphocytosis with circulating hallmark binucleated lymphocytes and elevated polyclonal serum IgM. Most patients have benign clinical course on long-term follow-up. Some pathologic features of PPBL may resemble malignant lymphoma, including morphology as well as frequent cytogenetic and molecular abnormalities. Significant symptomatic splenomegaly requiring splenectomy is very unusual for this disorder; therefore there is a lack of descriptions of the morphologic features of the spleen in the literature. We present here one of the first detailed descriptions of the morphologic and immunohistochemical features of the spleen from a young female with PPBL who developed massive splenomegaly during 6-year follow up. Splenectomy was performed for symptomatic relief and suspicion of malignant process. The morphological and immunohistochemical features of the spleen closely mimicked involvement by B-cell lymphoma, however there was no monotypic surface light chain restriction seen by flow cytometry and no clonal rearrangement of IgH gene was detected by molecular analysis. Evaluating a splenectomy sample in cases like this may present a diagnostic challenge to pathologists. Therefore, correlation with B cell clonality studies (by flow cytometry and molecular analysis), clinical findings and peripheral blood morphology searching for characteristic binucleated lymphocytes is essential to avoid misdiagnosing this benign process as B-cell lymphoma. We also present here a literature review on pathogenesis of PPBL.

Early lesions in lymphoid neoplasia: Conclusions based on the Workshop of the XV. Meeting of the European Association of Hematopathology and the Society of Hematopathology, in Uppsala, Sweden

The increasing use of immunophenotypic and molecular techniques on lymphoid tissue samples without obvious involvement by malignant lymphoma has resulted in the increased detection of "early" lymphoid proliferations, which show some, but not all the criteria necessary for a diagnosis of malignant lymphoma. In most instances, these are incidental findings in asymptomatic individuals, and their biological behaviour is uncertain. In order to better characterize these premalignant conditions and to establish diagnostic criteria, a joint workshop of the European Association for Haematopathology and the Society of Hematopathology was held in Uppsala, Sweden, in September 2010. The panel reviewed and discussed more than 130 submitted cases and reached consensus diagnoses. Cases representing the nodal equivalent of monoclonal B-cell lymphocytosis (MBL) were discussed, as well as the "in situ" counterparts of follicular lymphoma (FL) and mantle cell lymphoma (MCL), topics that also stimulated discussions concerning the best terminology for these lesions. The workshop also addressed the borderland between reactive hyperplasia, and clonal proliferations such as pediatric marginal zone lymphoma and pediatric FL, which may have very limited capacity for progression. Virus-driven lymphoproliferations in the grey zone between reactive lesions and manifest malignant lymphoma were covered. Finally, early manifestations of T-cell lymphoma, both nodal and extranodal, and their mimics were addressed. This workshop report summarizes the most important conclusions concerning diagnostic features, as well as proposals for terminology and classification of early lymphoproliferations and tries to give some practical guidelines for diagnosis and reporting.

Bcl-2 and Immunoglobulin Gene Rearrangements in Patients with Malaria Related Chronic Splenomegaly

Two cases of malaria related chronic splenomegaly, one with tropical splenic lymphoma with villous lymphocytes (TSLVL) and the other with hyperreactive malarial splenomegaly (HMS) were analyzed by cytology, histology, karyotyping, immunophenotyping, and polymerase chain reaction (PCR) for detection of bcl-2/JH and FR3/JH rearrangements on blood and bone marrow samples, at diagnosis and 12 months after malarial prophylaxis. The reported data suggest that the detection of FR3/JH rearrangement might contribute to the diagnosis of TSLVL in patients with malaria related chronic splenomegaly, for whom bcl-2/JH rearrangement may be a common molecular event.

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.

Selective defect of anti-pneumococcal IgG in a patient with persistent polyclonal B cell lymphocytosis

BACKGROUND

Persistent polyclonal B cell lymphocytosis (PPBL) is a rare condition characterized by increased IgM and large excess of B cells with an IgD(+) CD27(+) phenotype. In normal individuals, these cells play a central role in the defense against pneumococcal infection. So far, few studies have characterized humoral immune responses in PPBL patients. We therefore measured IgG directed against S. pneumoniae antigens in a 51 yr-old woman with PPBL before and after vaccination with a pneumococcal 23-valent polysaccharide vaccine.

METHODS

Antibodies against pneumococcal antigens were measured first with an overall immunoassay using microplates coated with the 23-valent pneumococcal vaccine. A serotype-specific test was also performed according to the WHO consensus protocol.

RESULTS

Despite a large number of IgD(+) CD27(+) cells, our patient had low baseline titers of IgG directed against pneumococcal antigens and did not significantly respond to a 23-valent polysaccharide vaccine against S. pneumoniae. On the contrary, she had good titers of IgG directed against tetanus toxoid.

CONCLUSION

IgM(+) IgD(+) CD27(+) cells which accumulate in this patient with typical PPBL patient failed to perform IgG isotype switch after a polysaccharide vaccine. The potential mechanisms and relationships with the main features of PPBL are discussed. Further studies on a larger number of similar patients are needed.

Polyclonal B-cell lymphocytosis with binucleated lymphocytes (PPBL)

Persistent polyclonal B-cell lymphocytosis (PPBL) is a rare and recently described entity. The review of the literature show PPBL is diagnosed predominantly but not exclusively in women, usually smokers. PPBL is recognized by a moderate, chronic and absolute lymphocytosis (>4 × 10(9)/l) in the peripheral blood. In 10% of cases without lymphocytosis, the PPBL diagnosis has to be suggested by peripheral blood examination showing in all cases atypical binucleated lymphocytes. A polyclonal serum IgM is also associated and HLA-DR7 expression is present in most cases. Contrary to B-cell chronic lymphoproliferative disorders (B-CLPD), peripheral B cells are polyclonal with kappa and lambda light-chain expression and no clonal rearrangement of immunoglobulin heavy chain genes is usually demonstrated. The detection of an extra isochromosome for the long arm of chromosome 3 +i(3)(q10) has to be considered as a specific marker of PPBL. We performed conventional cytogenetic analysis (CCA) in 111 patients with typical PPBL we followed-up more than 4 years. +i(3q) was detected in 34% (33/98), PCC in 8% (8/98) and both abnormalities in 31% (30/98). CCA showed neither +i(3q) nor PCC in 28% (27/98). Fluorescence in situ hybridization (FISH) was also performed in 84 cases and +i(3q) was detected in 71% (60/84). When combining both procedures in 84 patients, +i(3q) was detected in 17 patients with negative CCA and was confirmed in 43 patients with positive CCA. CCA and FISH were both negative in 24 cases. Whether patients with PPBL are at increased risk of hematological malignancy remains unclear. After a median follow-up of 4.4 years, most PPBL patients presented a stable clinical and biological course. Six patients died from pulmonary cancer, myocardial infarction, cerebral aneurysm rupture or diffuse large B-cell lymphoma. Two patients had IgM monoclonal gammopathy of undetermined significance (MGUS) at the time of PPBL diagnosis and two other patients developed IgM MGUS respectively 12 and 22 years after PPBL diagnosis. A malignant non Hodgkin's lymphoma (NHL) appeared in 3 additional patients: two patients presented diffuse large B cell lymphoma and 1 patient a splenic marginal zone lymphoma. In conclusion, the possibility of PPBL to evolve toward a clonal proliferation, malignant lymphoma or secondary solid cancer lead us to consider PPBL not as a benign pathology. We recommend a careful and continued clinical and biological long-term follow-up in all PPBL patients.

Intravascular bone marrow accumulation in persistent polyclonal lymphocytosis: a misleading feature for B-cell neoplasm

Persistent polyclonal B-cell lymphocytosis is usually reported in young smoking women. Whether this syndrome represents a premalignant or benign disease remains unclear. Indeed, because of the association of Bcl-2/IgH rearrangement and cytogenetic abnormalities, such cases may be misdiagnosed as the leukemic phase of a non-Hodgkin's lymphoma. We report eight new cases of persistent polyclonal B-cell lymphocytosis, which displayed a misleading bone marrow histological pattern, that is, intravascular B-cell infiltrate, constantly associated with Bcl-2 immunohistostaining, as seen in some lymphoma. We also show the absence or low expression of adhesion molecules on persistent polyclonal B-cell lymphocytes, suggesting that migration abnormalities might lead to bone marrow and peripheral blood accumulation. Although most cases presented multiple Bcl-2/IgH gene rearrangements and appeared to be polyclonal, oligoclonal expansion was identified in one out of eight patients, yet was not associated with clinical aggressiveness. The occasional reports of oligoclonal IgH and Bcl-2/IgH rearrangements in this disorder suggest that polyclonal expansion may be followed by the emergence of a predominant clone. However, the benign clinical course and lack of biological evolution in most cases imply that it is mandatory to distinguish this disorder from other malignant lymphoproliferations, so that unnecessary aggressive therapy can be avoided.

Detection of bcl-2/J(H) translocation by polymerase chain reaction: a summary of the experience of the Molecular Oncology Survey of the College of American Pathologist

CONTEXT

The t(14;18)(q32;;t6q21) translocation, found in about 85% of follicular lymphomas, brings the bcl-2 gene on 18q21 under control of the immunoglobulin heavy-chain gene transcriptional regulatory elements on 14q32. Detection of this translocation in a clinical sample suspected of containing lymphoma can assist the pathologist in diagnosis and classification of lymphoma. Polymerase chain reaction is a technology that is frequently used to detect the t(14;18)(q32;q21) translocation (bcl-2/J(H)). This article reviews the utility of polymerase chain reaction testing for bcl-2/J(H) detection and summarizes the experience of participants in the Molecular Oncology Proficiency Survey of the College of American Pathologists from 1997 through 2000.

OBJECTIVE

To describe current practice and encourage improvement of bcl-2/J(H) testing in clinical laboratories.

DESIGN

Retrospective analysis of Molecular Oncology Proficiency Survey data.

PARTICIPANTS

Laboratory participants in the College of American Pathology Molecular Oncology Proficiency Survey.

RESULTS

Twenty-four well-characterized specimens were sent to participants, of which 6 contained bcl-2/J(H) major breakpoint region translocations. Eight hundred nineteen major breakpoint region and 323 minor cluster region determinations were performed, with an overall correct response rate of 91% and 94%, respectively. No significant difference in correct response could be found for frozen versus paraffin-embedded tissues. Many laboratories did not know their assay sensitivity.

CONCLUSION

Overall performance was good; however, there was great variability in the methods reported and lack of knowledge of the limits of detection was common. Continued participation in external quality control programs, such as the Molecular Oncology Survey; dissemination of information that impacts on test performance; and technical recommendations from the molecular diagnostics community are critical for improved testing for bcl-2/J(H).

Persistent polyclonal B-cell lymphocytosis: further evidence for a genetic disorder associated with B-cell abnormalities

Persistent polyclonal B-cell lymphocytosis (PPBL) is an intriguing disorder diagnosed predominantly in women, usually cigarette smokers, characterized by an increase in the number of polyclonal B lymphocytes. Abnormality of the B-cell population is also evidenced by the presence of multiple bcl-2/Ig gene rearrangements and the finding of an additional long arm chromosome 3q+ (i3)(q10) within a significant proportion of B cells. The physiopathology of PPBL is unknown but its association with the HLA DR7 phenotype suggests a possible genetic disorder. To further determine whether PPBL has a genetic predisposition, we have undertaken an extensive study in a large family of a patient diagnosed with PPBL. Three individuals among the first-degree relatives presented all the criteria for a diagnosis of PPBL. A slight increase in serum IgM without evidence of B-cell proliferation was shown in two additional siblings. Multiple bcl-2/Ig gene rearrangements, a typical feature of PPBL, were identified in 8/10 individuals among first-degree relatives. A statistically significant association was found between the presence of these rearrangements and of a paternal HLA haplotype. We conclude that PPBL has a familial occurrence suggesting an underlying genetic defect. The development of the complete syndrome probably relies on unidentified additional co-factors.

Persistent polyclonal B-cell lymphocytosis is an expansion of functional IgD(+)CD27(+) memory B cells

Persistent polyclonal B-cell lymphocytosis (PPBL) is a rare disorder of unknown aetiology affecting predominantly young to middle-aged women. It is characterized by a polyclonal expansion of B cells, including typical binucleated lymphocytes, and is associated with the presence of the translocation t(14;18), involving the bcl-2 oncogene. The stage of differentiation of the B cells expanded in PPBL is not known. We analysed the immunophenotype of the expanded B-cell subset in five new patients with PPBL and found a large uniform expansion of a recently defined human memory B-cell population, IgD(+)CD27(+) memory B cells. After in vitro stimulation with interleukin 2 (IL-2) and Staphylococcus aureus Cowan strain I, B cells from PPBL patients produced high levels of IgM immunoglobulins, which is a characteristic feature of IgD(+)CD27(+) memory B cells. Using a quantitative real-time polymerase chain reaction method, we found a high frequency of the translocation t(14;18) in the range of 1000-3000 per 106 B cells in PPBL patients. In contrast, a much smaller number of cells with a t(14;18) was found in B cells from healthy individuals. Our finding that PPBL is an accumulation of memory B cells further suggests that chronic antigeneic stimulation plays an important part in the pathogenesis of this disorder. This IgD(+)CD27(+) memory B-cell population might harbour a certain number of 'physiological' t(14;18) translocations that increases as this population expands in PPBL patients and constitutes the majority of peripheral blood lymphocytes.

Persistent polyclonal B lymphocytosis: morphological, immunological, cytogenetic and molecular analysis of an Italian case

We describe a case of persistent polyclonal B-cell lymphocytosis (PPBL) studied by morphological, immunological, cytogenetic and molecular analysis. PPBL is a rare lymphoproliferative disorder with an unclear natural history. Although a few cases of malignancies are observed during PPBL, this disorder is usually considered to be an indolent syndrome. A longer follow-up in a larger number of patients is needed in order to clarify the natural history of PPBL and its potential to transform into a malignancy. As PPBL is a rare disease, establishing an international PPBL registry could be the most effective way to understand the natural history of this disease and to discover its etiologic factors.

An unusual form of persistent polyclonal B lymphocytosis in an infant

We report a case of persistent polyclonal lymphocytosis in an infant. The circulating lymphocytes were of a small to medium size and a small proportion were larger and had lymphoplasmacytoid features. The presence of either an infectious or mutagenic agent was excluded. The polyclonal B-cell nature of the lymphocyte was demonstrated by immunological markers and confirmed by Southern blot analysis and by polymerase chain reaction targeting immunoglobulin genes. In contrast to the common form of polyclonal lymphocytosis, this case was not associated with HLA-DR7 and/or abnormalities of chromosome 3, p53 or Bcl2/IgH. Whether this lymphocytosis represents a premalignant or a benign condition remains uncertain, although there has been no progression to date.

Biclonal chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is well characterized clinically and immunophenotypically. Demonstration of a monotypic CD19+, CD5+ B-cell population is central to the diagnosis. We report 2 cases of biclonal CLL. Two elderly men were encountered with an absolute lymphocytosis consisting of the typical CD5+, CD19+, CD23+ B-cell population seen in CLL; however, immunoglobulin light chain restriction by flow cytometry was not apparent as B cells expressed kappa or lambda light chains without a clear monotypic population. Molecular genetic analysis of flow cytometry-sorted cells (kappa and lambda populations) revealed in both cases 2 monoclonal B-cell populations. The characterization of these cases and a review of the issues surrounding biclonal CLL are presented.