Nodal marginal zone B-cell lymphomas may arise from different subsets of marginal zone B lymphocytes

IGHV mutational status of nodal marginal zone lymphoma by NGS reveals distinct pathogenic pathways with different prognostic implications

The precise B cell of origin and molecular pathogenesis of nodal marginal zone lymphoma (NMZL) remain poorly defined. To date, due to the rarity of NMZL, the vast majority of already-published studies have been conducted on a limited number of samples and the technical approach to analyze the immunoglobulin genes was of amplifying rearranged variable region genes with the classical direct sequencing of the PCR products followed by cloning. Here, we studied the B cell Ig heavy-chain repertoires by next-generation sequencing (NGS) in 30 NMZL cases. Most of the cases were mutated (20/28; 71.5%) with homologies to the respective germ line genes ranging from 85 to 97, 83%, whereas 8/28 (28.5%) were unmutated. In addition, our results show that NMZL cases have a biased usage of specific immunoglobulin heavy-chain variable (IGHV) region genes. Moreover, we documented intraclonal diversity in all (100%) of the mutated cases and ongoing somatic hypermutations (SHM) have been confirmed by hundreds of reads. We analyzed the mutational pattern to detect and quantify antigen selection pressure and we found a positive selection in 4 cases, whereas in the remaining cases there was an unspecific stimulation. Finally, the disease-specific survival and the progression-free survival were significantly different between cases with mutated and unmutated IGHV genes, pointing out mutational status as a possible new biomarker in NMZL.

Recent advances in understanding the biology of marginal zone lymphoma

There are three different marginal zone lymphomas (MZLs): the extranodal MZL of mucosa-associated lymphoid tissue (MALT) type (MALT lymphoma), the splenic MZL, and the nodal MZL. The three MZLs share common lesions and deregulated pathways but also present specific alterations that can be used for their differential diagnosis. Although trisomies of chromosomes 3 and 18, deletions at 6q23, deregulation of nuclear factor kappa B, and chromatin remodeling genes are frequent events in all of them, the three MZLs differ in the presence of recurrent translocations, mutations affecting the NOTCH pathway, and the transcription factor Kruppel like factor 2 ( KLF2) or the receptor-type protein tyrosine phosphatase delta ( PTPRD). Since a better understanding of the molecular events underlying each subtype may have practical relevance, this review summarizes the most recent and main advances in our understanding of the genetics and biology of MZLs.

Follicular Colonization of Nodal Marginal-Zone B-Cell Lymphoma Resembling Follicular Lymphoma: Report of 6 Cases

The formation of neoplastic B-cell follicles is accepted as a diagnostic criterion of follicular lymphoma. However, extranodal marginal-zone B-cell lymphomas (MZBLs) of mucosa-associated lymphoid tissue (MALT) type also sometimes contain numerous lymphoid follicles and may even have a predominantly follicular growth pattern. However, morphologic, immunohistochemical, and genotypic findings suggest that lymphoid follicles in extranodal MZBLs are neoplastic follicles formed as the result of colonization of previously reactive follicles by tumor cells (centrocyte-like cells). We present here 6 cases of nodal MZBL demonstrating a follicular growth pattern. Immunohistochemical study demonstrated that the tumor cells were CD10-, CD20+, CD79a+,CD 138-, Bcl-2+, Bcl-6and IRF4+. Residual nonneoplastic follicular center cells were CD1O+, CD20+, CD79a+, Bcl-2-, and Bcl-6+. CD21/CD23 immunostain demonstrated a disrupted follicular dendritic cell pattern characteristic of follicular colonization in extranodal MZBL of MALT type. Taken in conjunction with the morphologic findings, nodal MZBL may also show a follicular growth pattern similar to extranodal MZBL of MALT type. The marginal-zone nature is most recognizable on immunohistochemistry, although the histologic appearance alone may cause some diagnostic problems. It is important for pathologists to consider this type of lesion in diagnostic practice.

The bendamustine plus rituximab regimen is active against primary nodal marginal zone B-cell lymphoma

Primary nodal marginal zone lymphoma (NMZL) is a rare disease. There is no current consensus on how to treat it. The bendamustine plus rituximab (BR) regimen is effective for the treatment of follicular and other indolent lymphomas, but its efficacy in NMZL is not known. We analyzed the outcome of 14 patients diagnosed with NMZL (median age 67 years) who were treated with 375 mg/m² of rituximab on day 1 and 90 mg/m² of bendamustine on days 1 and 2. The overall and complete response rates were 93% and 71%, respectively. Major toxicity (grade 3/4 neutropenia) occurred in 5% of treatment courses. After a median follow-up of 22 months (range: 18-55), the overall survival and the free survival rates were 100% and 93%, respectively. None of the patients showing a complete or partial response developed secondary myelodysplastic syndrome/acute myeloid leukemia. Bendamustine plus rituximab was found to be an active and well-tolerated regimen leading to the rapid control of disease.

Optimizing therapy for nodal marginal zone lymphoma

Nodal marginal zone lymphoma (NMZL) is a rare form of indolent small B-cell lymphoma which has only been clearly identified in the last 2 decades and which to date remains incurable. Progress in therapeutic management has been slow, largely due to the very small number of patients treated and the heterogeneity of treatments administered; thus, standard-of-care treatment is currently nonspecific for this lymphoma entity. In this review, treatments routinely used to manage adult NMZL patients are presented, principally based on immunochemotherapy (when treatment is needed). Biological research behind the key axes of agents currently under development is described; development of novel agents is heavily based on data from gene profiling and genome-wide sequencing research, uncovering a number of critical deregulated pathways specific to NMZL tumors. These include B-cell receptor, JAK/STAT, NF-κB, NOTCH, and Toll-like receptor signaling pathways, as well as intracellular processes such as the cell cycle, chromatin remodeling, and transcriptional regulation in terms of epigenetic modifiers, histones, or transcriptional co-repressors, along with immune escape via T-cell-mediated tumor surveillance. These pathways are examined in detail and a projection of how the field may evolve in the near future for an efficient personalized treatment approach for NMZL patients is presented.

MicroRNA profiling of low-grade and transformed nodal marginal zone lymphoma reveals a similar signature pattern distinct from diffuse large B cell lymphoma

BACKGROUND/AIMS

As critical post-transcriptional regulators of gene expression, microRNAs are involved in several cellular processes of vital impact including cell growth and apoptosis. Many hematologic malignancies exhibit distinct microRNA signatures. MicroRNA implication in the pathogenesis of nodal marginal zone lymphoma (NMZL), however, remains widely elusive.

METHODS

Comprehensive morphologic, immunophenotypic and cytogenetic studies were carried out on a cohort of NMZL (n = 30) incorporating indolent as well as transformed MZL. In addition, microRNA signatures were generated, employing a quantitative real-time polymerase chain reaction approach. These were then compared to signatures from cases of diffuse large B cell lymphoma (DLBCL) alongside reactive lymph node controls.

RESULTS

While microRNA signatures of low-grade and transformed NMZL did not differ significantly, several microRNAs were differentially expressed between transformed NMZL and DLBCL, hinting at molecularly distinct mechanisms of lymphomagenesis and indicating the biological disparity of transformed NMZL from DLBCL.

CONCLUSION

In the light of the unresolved issue regarding the classification of marginal zone-derived transformed B-cell neoplasms, microRNAs may be a valuable aid in discriminating NMZL from DLBCL.

Recognizing nodal marginal zone lymphoma: recent advances and pitfalls. A systematic review

The diagnosis of nodal marginal zone lymphoma is one of the remaining problem areas in hematopathology. Because no established positive markers exist for this lymphoma, it is frequently a diagnosis of exclusion, making distinction from other low-grade B-cell lymphomas difficult or even impossible. This systematic review summarizes and discusses the current knowledge on nodal marginal zone lymphoma, including clinical features, epidemiology and etiology, histology, and cytogenetic and molecular features. In particular, recent advances in diagnostics and pathogenesis are discussed. New immunohistochemical markers have become available that could be used as positive markers for nodal marginal zone lymphoma. These markers could be used to ensure more homogeneous study groups in future research. Also, recent gene expression studies and studies describing specific gene mutations have provided clues to the pathogenesis of nodal marginal zone lymphoma, suggesting deregulation of the nuclear factor kappa B pathway. Nevertheless, nodal marginal zone lymphoma remains an enigmatic entity, requiring further study to define its pathogenesis to allow an accurate diagnosis and tailored treatment. However, recent data indicate that it is not related to splenic or extranodal lymphoma, and that it is also not related to lymphoplasmacytic lymphoma. Thus, even though the diagnosis is not always easy, it is clearly a separate entity.

Clinicopathologic features of CD5-positive nodal marginal zone lymphoma

OBJECTIVES

To describe the clinicopathologic findings of seven patients with CD5-positive nodal marginal zone lymphoma (NMZL).

METHODS

We searched cases of NMZL over a 10-year interval and identified seven cases of CD5-positive NMZL. The clinical, histologic, and immunophenotypic findings of this group were reviewed, and the frequency of dissemination in this group was compared with that of 66 patients with CD5-negative NMZL.

RESULTS

Other than CD5 expression, the histologic and immunophenotypic findings were typical of NMZL. Six (86%) of seven patients had lymphadenopathy above and below the diaphragm, and all six patients assessed had bone marrow involvement. In the CD5-negative group, 28 (42%) patients had lymphadenopathy above and below the diaphragm, and 36 (55%) had bone marrow involvement (P = .045 and P = .037, respectively). Six of seven patients were alive at last follow-up, with a median follow-up of 32 months (3-154 months).

CONCLUSIONS

CD5 expression in NMZL correlates with a higher frequency of dissemination, but patients have an indolent clinical course and excellent overall survival.

T(11;18)(q21;q21)-positive gastrointestinal MALT lymphomas are heterogeneous with respect to the VH gene mutation status

AIM: To investigate how t(11;18)(q21;q21)-positive gastrointestinal MALT lymphomas relate to other marginal zone lymphomas with respect to the somatic mutation pattern of the V_H genes and the expression of the marker CD27.

METHODS: The V_H gene of 7 t(11;18)(q21;q21)-positive gastrointestinal MALT lymphomas was amplified by PCR using family specific V_H primers and a consensus J_H primer. PCR products were sequenced and mutation analysis of the CDR and the FR regions was performed. All cases were immunostained for CD27.

RESULTS: One case showed unmutated V_H genes while the others showed mutated V_H genes with mutation frequencies ranging from 1.3 to 14.7% and with evidence of antigen selection in 2 cases. These data suggest that the translocation t(11;18)(q21;q21) can target either B-cells at different stages of differentiation or naive B-cells that retain the capacity to differentiate upon antigen stimulation. All cases but one displayed weak to strong CD27 expression which did not correlate with the V_H gene mutation status.

CONCLUSION: t(11;18)(q21;q21)-positive gastrointestinal MALT lymphomas are heterogeneous with respect to the V_H mutation status and CD27 is not a marker of somatically mutated B-cells.

Genome-wide DNA profiling of marginal zone lymphomas identifies subtype-specific lesions with an impact on the clinical outcome

Marginal zone B-cell lymphomas (MZLs) have been divided into 3 distinct subtypes (extranodal MZLs of mucosa-associated lymphoid tissue [MALT] type, nodal MZLs, and splenic MZLs). Nevertheless, the relationship between the subtypes is still unclear. We performed a comprehensive analysis of genomic DNA copy number changes in a very large series of MZL cases with the aim of addressing this question. Samples from 218 MZL patients (25 nodal, 57 MALT, 134 splenic, and 2 not better specified MZLs) were analyzed with the Affymetrix Human Mapping 250K SNP arrays, and the data combined with matched gene expression in 33 of 218 cases. MALT lymphoma presented significantly more frequently gains at 3p, 6p, 18p, and del(6q23) (TNFAIP3/A20), whereas splenic MZLs was associated with del(7q31), del(8p). Nodal MZLs did not show statistically significant differences compared with MALT lymphoma while lacking the splenic MZLs-related 7q losses. Gains of 3q and 18q were common to all 3 subtypes. del(8p) was often present together with del(17p) (TP53). Although del(17p) did not determine a worse outcome and del(8p) was only of borderline significance, the presence of both deletions had a highly significant negative impact on the outcome of splenic MZLs.

Non-gastric marginal zone B-cell lymphoma in Korea: clinical features, treatment, and prognostic factors

Marginal zone B-cell lymphoma (MZL) is the second most common subtype of non-Hodgkin's lymphoma in Korea (17.3%). Mucosa-associated lymphoid tissue (MALT) can develop in almost any organ as a result of exposure to a persistent stimulus, such as chronic infection or certain autoimmune processes. Under conditions of prolonged lymphoid proliferation, a malignant clone may emerge, which is followed by the development of a MALT lymphoma. Whereas MALT lymphoma of the stomach is the most common and the most extensively studied, we focus on non-gastric MZL studies conducted in Korea that highlight the most recent advances with respect to MZL definition, etiology, clinical characteristics, natural history, treatment approaches, outcomes, and prognostic factors. Moreover, we discuss current organ-specific considerations and controversies, and identify areas for future research.

Immunoarchitectural patterns in nodal marginal zone B-cell lymphoma: a study of 51 cases

Nodal marginal zone lymphoma (NMZL) represents a rare and heterogeneous group that lacks markers specific for the diagnosis. We evaluated morphologic and immunoarchitectural features of 51 NMZLs, and the following immunostains were performed: CD20, CD21, CD23, CD5, CD3, CD43, CD10, Ki-67, BCL1, BCL2, BCL6, HGAL, and LMO2. Four immunoarchitectural patterns were evident: diffuse (38 [75%]), well-formed nodular/follicular (5 [10%]), interfollicular (7 [14%]), and perifollicular (1 [2%]). Additional features included a monocytoid component (36 [71%]), admixed large cells (20 [39%]), plasma cells (24 [47%]), compartmentalizing stromal sclerosis (13 [25%]), and prominent blood vessel sclerosis (10 [20%]). CD21 highlighted disrupted follicular dendritic cell meshwork in 35 (71%) of 49 cases, and CD43 coexpression was present in 10 (24%) of 42 cases. A panel of germinal center-associated markers was helpful in eliminating cases of diffuse follicle center lymphoma. Our results highlight the histologic and immunoarchitectural spectrum of NMZL and the usefulness of immunohistochemical analysis for CD43, CD23, CD21, BCL6, HGAL, and LMO2 in the diagnosis of NMZL.

Radiotherapy for 41 patients with stages I and II MALT lymphoma: a retrospective study

PURPOSE

Mucosa-associated lymphoid tissue (MALT) lymphoma is a distinct disease with specific clinical and pathologic features that may affect diverse organs. We analyzed our recent experience with Stage I/II MALT lymphoma presenting in the stomach and other organs to assess the outcome following radiation therapy (RT) alone.

PATIENTS AND METHODS

Forty-one patients with Stages I (37) and II (4) disease were treated between 2000 and 2006. Patients with transformed MALT were excluded. The median age was 60 years (range, 25-86 years), male: female ratio 1:1. Presenting sites included stomach, 11; orbital adnexa, 21; thyroid, 1; other head and neck, 3; small bowel, 3; skin, 1; and rectum, 1. Thirty-five patients (85%) received RT-alone and 6 (15%) received antibiotics followed by RT. RT dose was 30Gy in 20 fractions (fr) in all 41 patients. Mean follow-up time was 32.0 months (range, 2.1-162 months).

RESULTS

A first complete response was achieved in all 41 patients. Only one patient died from bile duct carcinoma at 22 months from the start of irradiation for conjunctiva MALT lymphoma without recurrence of lymphoma. The other 40 patients were alive. Thirty-eight patients out of them were alive without recurrence. One patient with a duodenal lymphoma had a recurrence in non-irradiated distant sites at 1 month. Another patient with a bilateral eye lid lymphoma had a recurrence within radiation field at 41 months. The absolute local control rate with radiation was 98% (40/41 patients).

CONCLUSION

Localized MALT lymphomas have excellent prognosis following moderate-dose RT (30Gy/20fr).

Marginal Zone Lymphomas: Management of Nodal, Splenic, and MALT NHL

Marginal zone lymphomas are indolent B-cell lymphomas that originate from the marginal zone of B-cell follicles. For several subtypes, the initiation of disease appears to be a consequence of chronic infection and/ or inflammation. While the initial lymphoid hyperplasia is driven by physiologic antigenic stimulation, additional oncogenic events, such as chromosomal translocations leading to constitutive activation of signaling pathways, occur during the progression of disease that ultimately result in antigen-independent lymphoproliferation. Despite having a common origin in the marginal zone of the B-cell follicle, there are distinct clinical and molecular characteristics of marginal zone lymphomas originating at different anatomic sites. As such, marginal zone–derived lymphomas are currently categorized by the World Health Organization (WHO) into those originating in the spleen (splenic marginal zone lymphoma), extranodal mucosa-associated lymphoid tissue (MALT lymphoma), or lymph node (nodal marginal zone lymphoma).

Nongastric marginal zone B-cell lymphoma: analysis of 247 cases

Nongastric marginal zone B-cell lymphoma (NG-MZL) is a relatively uncommon indolent lymphoma. From 1990 to 2005, a total of 247 patients with histologically confirmed NG-MZL were analyzed. Ann Arbor stage I/II disease was present in 78% (167 out of 215). One hundred eighty-six patients out of two hundred eight were categorized into the low/low-intermediate risk group (89%) according to International Prognostic Index (IPI). Eighty percent (172/215) were in low risk group according to Follicular Lymphoma International Prognostic Index (FLIPI). Complete and partial remissions (CR and PR) were achieved in 140 (92.7%) and 8 (5.3%) of the 151 stage I/II patients. Especially, radiation containing treatment achieved 96% CR rate (108 out of 113). In 38 patients with stage III/IV, CR and PR were achieved in 17 (44.7%) and 11 (26.3%), respectively. The estimated five-year overall survival (OS) and progression-free survival (PFS) were 93.8% and 70.1%, respectively. Although anthracycline-containing regimen could achieve higher CR rate, it did not improve PFS. Stage III/IV, low hemoglobin, poor performance status, high/high-intermediate IPI, poor risk FLIPI, and nodal MZL were poor prognostic factors for PFS. NG-MZL is an indolent disease. FLIPI has strong power to predict the prognosis of NG-MZL.

Immunoglobulin VH gene analysis in gastric MALT lymphomas

The majority of gastric mucosa-associated lymphoid tissue (MALT) lymphomas are successfully treated with Helicobacter pylori eradication alone. However, certain subsets of these tumors are resistant to the eradication treatment. As API2-MALT1 fusion is a feature of one of these subsets, we divided gastric MALT lymphomas into three groups: eradication-responsive and API2-MALT1 fusion-negative (Group A), eradication-resistant and fusion-negative (Group B), and eradication-resistant and fusion-positive (Group C). To characterize further gastric MALT lymphomas, we analyzed VH genes, which do not change in the course of tumor progression, by extensive subcloning of the monoclonal PCR products of 45 cases. VH3-23 and VH3-30 were preferentially used in Group A tumors (14/23 cases, 61%) as compared with Group B (1/10 cases, 10%, P=0.0094) and Group C (2/12 cases, 17%, P=0.017). Tumors of Groups B and C used variegated VH fragments, and no dominant VH fragments were noted. Somatic mutation was detected in most of the cases. Ongoing mutation was detected in 3/45 cases (7%), when assessed according to strict criteria for a confirmed mutation. These findings suggest that inflammation-dependent tumors (Group A) may be derived from a highly restricted, probably H. pylori-associated, B cell subset and may not often progress to those that are inflammation-independent (Groups B and C). Although considered to be common in this tumor, ongoing mutation may be infrequent when assessed by strict criteria.

Primary nodal marginal zone B-cell lymphoma: clinical features and prognostic assessment of a rare disease

This study defined the clinical features and assessed the prognosis of 47 patients (17 males, 30 females, median age 63 years) with primary nodal marginal zone B-cell lymphoma. Forty-five per cent had stage IV disease. Hepatitis C virus serology was positive in 24%. According to the Follicular Lymphoma International Prognostic Index (FLIPI), 33% were classified as low-risk, 34% as intermediate-risk, and 33% as high-risk. The 5-year overall survival (OS) was 69%. In univariate analysis worse OS was associated with: FLIPI (P = 0.02), age > 60 years (P = 0.05) and raised lactate dehydrogenase (P = 0.05). In multivariate analysis, only FLIPI predicted a worse OS (P = 0.02).

Clinical implications of nodal marginal zone B-cell lymphoma among Japanese: study of 65 cases

To clarify the clinical presentation and outcome of nodal marginal zone B-cell lymphoma (NMZBL), 65 Japanese patients with this disease were studied and compared with the published literature from western countries. The clinical findings of our 65 cases were similar to those of their cases in some aspects: (1) 58% of the patients were > 60 years old (median age, 64 years); (2) there was a slight female predominance; (3) 90% of the patients exhibited asymptomatic lymphadenopathy in the head and neck area; (4) only a minority of patients had B symptoms (6%) and poor performance status (8%); and (5) only 5% of patients were positive for M-protein. However, the 65 patients in this series exhibited relatively longer 5-year overall survival (85%) and failure-free survival (60%) than the NMZBL series published in western literature, suggesting that NMZBL should be classified as indolent lymphoma. Moreover, based on the histological findings, we further classified four histological subtypes as follows: (1) splenic type (n = 7); (2) floral type (n = 9); (3) mucosa-associated lymphoid tissue (MALT) type (n = 29); and (4) diffuse large B-cell lymphoma (DLBCL) + MALT type (n = 20). DLBCL + MALT type exhibited significantly poorer 5-year overall survival than the splenic variant. The recognition of DLBCL + MALT type appears important. No API2-MALT1 fusion transcript was detected in any of the 14 cases examined.

Nodal marginal zone B-cell lymphoma: analysis of 36 cases. Clinical presentation and treatment outcomes of nodal marginal zone B-cell lymphoma

Nodal marginal zone B-cell lymphoma (NMZL) is a relatively uncommon type of lymphoma. Because of the rarity, the natural history and the optimal treatment modality have not been well defined. Therefore, we performed a retrospective analysis of the clinical features and treatment outcomes of NMZL. Thirty-six patients who were histologically diagnosed as NMZL were included in the analysis. Fifty-three percent of the patients had localized disease (stages I and II), and 21.2% (7/33) had bone marrow involvement at presentation. B symptom was present in only three patients (8.3%). Most patients were categorized as low or low-intermediate risk group by international prognostic index (IPI) (77.1%). Majority (94.4%) of the patients with localized disease achieved complete remission (CR) after the initial treatment. Of the seven patients with disseminated disease, who were treated with anthracycline-based chemotherapy, four patients achieved CR. Of the seven patients who received nonanthracycline-based chemotherapy, no patient achieved CR. After the median follow-up duration of 36 months, the median progression-free survival (PFS) was 3.9 (95% CI; 2.9-5.6) years, and the estimated 5-year PFS and overall survival rates were 47.2 and 82.7%, respectively. The significant predictive factors for PFS were performance status, advanced stage, and follicular lymphoma IPI (FLIPI) in this study. This clinical feature is similar to FL rather than to MZL-MALT type.

A clinicopathological study of nodal marginal zone B-cell lymphoma. A report on 21 cases

AIMS

To report the clinicopathological findings of 21 cases of primary nodal marginal zone B-cell lymphoma (NMZL). NMZL is a recently characterized lymphoma and few series have been published.

METHODS AND RESULTS

The clinical data were characteristic of a disseminated disease at presentation: presence of peripheral and abdominal lymph nodes, bone marrow involvement (62%), disease stage III and IV (76%), elevated lactate dehydrogenase (LDH) (48%). Other features included peripheral blood involvement (23%), anaemia (24%), thrombocytopenia (10%) and presence of serum M component (33%), while the previously reported association with hepatitis C virus and cryoglobulinaemia was not found. Relapses were frequent but the majority of patients receiving chemotherapy had a good initial response. Morphological features were heterogeneous and there were some differences compared with other marginal zone B-cell lymphomas (MZL). Pure monocytoid B-cell lymphomas were rare (10%) but a minor component of monocytoid B cell was observed more frequently (23%). Plasmacytoid or plasmacytic differentiation was a very common feature (61%). Large cells and a high mitotic count were also frequent (57%).

CONCLUSION

NMZL can be distinguished from splenic MZL and extranodal MZL by its aggressive morphology and disseminated disease at presentation.

ImmunoglobulinVH genes in thymic MALT lymphoma are biased toward a restricted repertoire and are frequently unmutated

Thymic MALT lymphoma shows certain distinctive features among MALT lymphomas, such as expression of IgA isotype, consistent lack of API2-MALT1 gene fusion, and very strong association with autoimmune disease, especially Sjogren's syndrome. To help clarify the nature of the clonal lymphoid infiltrates, we analysed the usage and somatic hypermutation of the Ig heavy chain variable region (V(H)) genes in nine different cases. The V(H) rearrangement was potentially functional in all cases and was restricted to the V(H)3 family. V(H) usage was biased toward V(H)3-30 (five cases) and V(H)3-23 (three cases) segments, which have both been frequently expressed by autoimmune B cells. Somatic hypermutation was absent in five cases. Fewer than the expected replacement mutations were found in the framework regions in two cases, indicating a negative antigen selection pressure. Ongoing mutation was absent in all cases. D segment usage was varied, whereas J(H) segment usage was restricted to J(H)4. The observed patterns of V(H) usage and mutations suggested that specific antigens may play a pathologically relevant role in the genesis or progression of thymic MALT lymphoma.

Clinicopathologic Features of Waldenström's Macroglobulinemia and Marginal Zone Lymphoma: Are They Distinct or the Same Entity?

Waldenstrom's macroglobulinemia (WM) is considered in the World Health Organization classification as a clinical syndrome associated with monoclonal immunoglobulin (Ig) M secretion, mainly observed in patients with lymphoplasmacytic lymphoma (LPL) and occasionally with other small B-cell lymphomas. Some authors consider it a rare distinct lymphoproliferative disorder with primary bone marrow infiltration and IgM monoclonal gammopathy. As LPL shares important morphologic and immunophenotypic overlaps with marginal zone B-cell lymphomas (MZLs) in cases showing plasmacytic maturation, it remains unclear if they constitute unique or distinct entities. Both diseases are composed of lymphocytes, lymphoplasmacytoid cells, and tumoral plasma cells with a surface (s) IgM-positive sIgD+/ cytoplasmic IgMpositive CD19+ CD20+ CD27+/ CD5 CD10 CD23 phenotype, without a specific marker. Extranodal mucosa-associated lymphoid tissue (MALT) lymphoma, nodal MZL (NMZL), and splenic MZL (SMZL) are distinct entities displaying common morphologic, immunophenotypic, and genetic characteristics. MALT lymphoma is clearly distinct from LPL, although bone marrow infiltration and IgM paraprotein are not rare. Splenic MZL and NMZL are incompletely characterized, but a plasmacytoid/plasmacytic differentiation, autoimmune manifestations, and monoclonal component are frequent in both diseases. Bone marrow involvement is constant in SMZL and present in 60% of NMZLs. Molecular IgVH gene analysis has confirmed this heterogeneity, particularly within SMZL, with mutated and unmutated cases. Further studies are needed to clarify the pathogenesis of these MZLs and their relationship with LPL.

Expression of the human germinal center-associated lymphoma (HGAL) protein, a new marker of germinal center B-cell derivation

We identified the human germinal center-associated lymphoma (HGAL) in gene-expression profiling studies of diffuse large B-cell lymphoma (DLBCL). The expression of HGAL correlated with survival in patients with DLBCL. The HGAL gene is the human homolog of M17, a mouse gene expressed specifically in normal germinal center (GC) B cells. We generated a monoclonal antibody against the HGAL protein and show that HGAL is expressed in the cytoplasm of GC lymphocytes and in lymphomas of GC derivation. Among 727 lymphomas tested by immunohistochemistry on tissue microarrays, HGAL staining was found in follicular lymphomas (103 of 107), Burkitt lymphomas (40 of 40), mediastinal large B lymphomas (7 of 8), and in DLBCLs (103 of 151). Most marginal zone lymphomas lacked HGAL staining. Lymphocyte-predominant Hodgkin lymphomas (12 of 17) and, surprisingly, classical Hodgkin lymphomas (78 of 107) were found to be positive. Hierarchical clustering of comparative immunohistologic results in DLBCLs demonstrates that the expression of HGAL is similar to 2 other GC-associated proteins, BCL6 and CD10, but different from 2 markers associated with a non-GC phenotype, MUM1/IRF4 and BCL2. The restricted expression and GC specificity of HGAL protein suggest that it may have an important role in the diagnosis of specific lymphomas, and, potentially in the identification of subtypes associated with different prognoses.

Indolent lymphoma: the pathologist's viewpoint

Indolent lymphomas have recently been the object of numerous studies, which have focused on new aspects relevant both for the better comprehension of their histogenesis and the identification of new therapeutic strategies. As marginal-zone lymphoma (MZL) represents the category of indolent lymphomas that has obtained more benefit from such an approach, the authors focused on the most recent achievements and not yet solved controversies in this area. In spite of their postulated common derivation, the three categories of MZL of the WHO Classification appear dissimilar. In fact, they show significant molecular differences among them as well as a certain heterogeneity within each group. By no means, there is a cogent need of more refined tools to revise these neoplasms and to produce a more rational grouping. The recent identification of the IRTA gene family corresponding to IG-like receptors differentially expressed in B-cells might contribute to their better understanding.

Rituximab: expanding role in therapy for lymphomas and autoimmune diseases

Rituximab (Rituxan) is a human-mouse chimeric monoclonal antibody that targets the B-cell CD20 antigen and causes rapid and specific B-cell depletion. Rituximab was approved in the United States in 1997 to treat low-grade or follicular, relapsed or refractory, CD20-positive B-cell non-Hodgkin's lymphoma (NHL). Since then, further clinical experience with rituximab has been incorporated into the prescribing information, which now stipulates an extended eight-week schedule, treatment of patients with refractory or relapsed bulky disease measuring >10 cm, and retreatment of patients who responded to rituximab previously. In 1998, the European Union approved rituximab (MabThera) to treat stage III/IV, follicular, chemotherapy-resistant, or relapsed NHL. Recently, the European Union also approved the use of rituximab in combination with standard chemotherapy for aggressive NHL. Many clinical trials have evaluated rituximab, alone or with other therapies, in indolent and aggressive NHL as well as other B-cell lymphoproliferative disorders. New studies are evaluating rituximab's role in first-line therapy, maintenance therapy, and stem-cell transplantation procedures. The use of rituximab against autoimmune disorders, such as rheumatoid arthritis, immune thrombocytopenic purpura, autoimmune hemolytic anemia, systemic lupus erythematosus, and multiple sclerosis, is also under investigation.

Update on gene therapy for hereditary hematological disorders

The past 3 years have been characterized by a number of impressive advances as well as setbacks in gene therapy for genetic disease. Children with X-linked severe combined immunodeficiency disorder (SCID-X1) have shown almost complete reconstitution of their immune system after receiving retrovirally transduced autologous CD34+ hematopoietic stem cells (HSCs). However, two of 11 treated patients subsequently developed a leukemia-like disease probablydue to the undesired activation of an oncogene. Gene transfer to HSCs resulted in substantial correction of immune function and multi-lineage engraftment in two patients with adenosine deaminase (ADA)-SCID. Several Phase I clinical trials for treatment of hemophilia A and B have been initiated or completed. Partial correction of hemophilia A, albeit transient, has been reported by ex vivo gene transfer to autologous fibroblasts. Intramuscular injection of adeno-associated viral (AAV) vector to patients with severe hemophilia B resulted in evidence of Factor IX gene transfer to skeletal muscle and a separate trial based on hepatic infusion of AAV vector is ongoing. Sustained therapeutic levels of coagulation factor expression have been achieved in preclinical models using retroviral, lentiviral, AAV and high capacity adenoviral vectors. Efficient lentiviral gene transfer to HSC in murine models of beta-thalassemia and sickle cell disease demonstrated sustained phenotypic correction.

Immunoglobulin heavy chain genes somatic hypermutations and chromosome 11q22-23 deletion in classic mantle cell lymphoma: a study of the Swiss Group for Clinical Cancer Research

Mantle cell lymphoma (MCL) shares immunophenotypic and karyotypic features with chronic lymphocytic leukaemia. The latter comprises two distinct entities with prognosis dependent upon immunoglobulin heavy chain (IgH) gene mutational status and the presence of 11q deletion. We evaluated the relevance of IgH gene mutational status, IgV gene family usage and presence of 11q deletion in a series of 42 histologically reviewed classical MCL cases to determine the prognostic impact. VH3 was the most common VH family, with VH3-21 being the most frequent individual VH gene. Approximately 30% of the cases had a IgH somatic mutation rate higher than 2%, but was only higher than 4% in <10% of cases. Half of the cases had deletion of chromosome 11q21-telomere (11q21->ter), with two minimal deleted regions, at 11q22.2 and 11q23.2. There was no association between 11q loss and IgH gene somatic mutation rate; the use of VH3-21 gene could be associated with a better prognosis.

Nodal marginal zone lymphoma: a heterogeneous tumor: a comprehensive analysis of a series of 27 cases

We have reviewed the clinical, morphologic, immunophenotypical, and molecular features of a series of 27 cases of nodal marginal zone lymphoma with the aim of defining this entity more precisely. The series was characterized by a relatively favorable clinical course, with a low clinical stage at diagnosis (59% patients with clinical stage I-II) and a 5-year overall survival probability of 79%. However, the disease persisted in a relatively large fraction of the patients, thus yielding a 5-year failure-free survival probability of 22%. Molecular and immunohistochemical analyses of the series revealed heterogeneity in the frequency of IgV(H) somatic mutation and in the expression of IgD, CD43, MUM1, and CD38. Apart from the absence of nuclear Bcl10, no clear distinction could be made from the expression profiling of other B-cell lymphomas claimed to be derived from marginal zone B cells. Additionally, the immunophenotype of the tumoral cells in all cases but one differed from that described in monocytoid B cells. It was characterized by a Bcl2-, p21+, cyclin E+ profile. The analysis of apoptosis-regulator proteins disclosed abnormalities in the expression of survivin and active caspase 3, which could partially explain the abnormal regulation of apoptosis observed in these tumors. Molecular and immunohistochemical data obtained in this study strongly imply that there is significant heterogeneity among the cases included in the category termed nodal marginal zone lymphoma.

Extranodal marginal zone B-cell lymphoma of MALT-type of the lung: single-center experience with 12 patients

The lung is a relatively rare site for mucosa-associated lymphoid tissue (MALT) lymphomas: we report the largest available single-center series of patients with this presentation. From August 1992 to October 2000, 12 patients with untreated primary low-grade MALT lymphoma of the lung were submitted either to chemotherapy alone (n = 8), surgery alone (n = 2) or surgery plus chemotherapy (n = 2). At diagnosis, 6 (50%) were asymptomatic and 6 (50%) had nonspecific pulmonary symptoms. The most common radiologic findings were a pulmonary infiltrate (7 cases) and a mass lesion (5 cases). Histological diagnosis was obtained with transbronchial lung biopsy/bronchoalveolar lavage (BAL) (6 cases), with transthoracic needle biopsy (1 case), or an open thoracotomy (5 cases). All patients had stage IE. All 12 (100%) achieved complete remission; 3 (25%) local recurrences were observed. The global 6-year survival rate was 100% with a relapse-free survival rate of 50%. In conclusion, these data underline the diagnostic utility of BAL and the therapeutic efficacy of a chemotherapeutic strategy based on regimens such as N-CVP in the context of localized MALT lymphoma of the lung.

Antibody therapy of non-Hodgkin's B-cell lymphoma

Engineering antibodies with reduced immunogenicity and enhanced effector functions, and selecting antigen targets with the appropriate specificity, density, and/or functionality, have contributed to the recent clinical successes in using unconjugated "naked" antibody therapies of B-cell lymphoma (rituximab) and breast carcinoma (Herceptin). The non-overlapping toxicities of naked antibodies and chemotherapy, together with their potential synergy, which is based on unique and complementary mechanisms of action, have contributed to the creation of new standards of care in cancer therapy and management. Clinical trial results supporting these concepts are presented. Furthermore, the exquisite specificity of antibodies renders them ideal vehicles for selective delivery of toxic payloads such as drugs or radionuclides. Although successful in therapy of hematological cancers (Zevalin, Mylotarg), the broader application of these technologies to carcinomas still remains to be proven in clinical testing. Engineering of antibody constructs with optimal blood clearance and tumor-targeting kinetics, and selecting the radionuclide that may deliver sufficient radiation energy to kill the more radio-resistant carcinomas, are discussed. With the advent of genomics and proteomics, new membrane-associated tumor antigens are being discovered and will provide novel targets for future antibody therapy of cancer.

Outcome in relation to treatment modalities in 48 patients with localized gastric MALT lymphoma: a retrospective study of patients treated during 1976-2001

The aim of this study was to retrospectively analyze survival and tumor response data in patients with localized gastric MALT lymphoma treated by different treatment modalities other than anti-Helicobacter pylori treatment (diagnosis made before 1993, or after failure of antibiotics + anti-acid), including surgery, chemotherapy or combined treatment. Here we studied a series of 48 patients with stage IE or IIE disease treated during the past 11 years. These patients received different treatments: chemotherapy was proposed to 19 (40%) patients; gastric surgery to 21 (43%) patients, consisting of partial gastrectomy of 7 patients and total gastrectomy in 14 patients; combined treatment to 8 (17%) patients, consisting of surgery + chemotherapy in 7 patients and surgery + chemotherapy + radiotherapy in 1 patient. At diagnosis, 85% of the patients had good PS and no B symptoms. Complete response after treatment was reached in 45 (94%) patients (chemotherapy: 84% of the patients; surgery alone: 95%; combined treatment: 100%). Progression was observed in 16 (33%) patients. No statistical difference in the survival was found among the different therapeutic modalities: 5-year overall survival year FFP survival was 81% for chemotherapy, 86% for surgery alone and 95% for combined treatment. Prognostic factors for survival were age, performance status and hemoglobin level at diagnosis. Considering the natural bias of a retrospective analysis, surgery or chemotherapy was associated with a similar outcome in patients with MALT lymphoma after antibiotics failure.

Splenic marginal zone lymphoma with villous lymphocytes shows on-going immunoglobulin gene mutations

Splenic marginal zone lymphoma (also splenic lymphoma with villous lymphocytes) is a B-cell non-Hodgkin's lymphoma with a characteristic morphology and phenotype. We studied the pattern of somatic hypermutation of the rearranged immunoglobulin heavy chain genes on 23 cases and have correlated these data with survival as well as immunophenotypic and genetic characteristics of the cases. Two-thirds of the cases show immunoglobulin gene mutations, half of which show evidence of antigen selection, whereas one-third of the cases show no significant mutations. On-going mutation, a feature characteristic of follicular lymphoma, was demonstrated in all six cases randomly selected for this analysis, including one case with a low number of mutations (<2%). No statistical significant correlation was found between immunoglobulin mutation status and clinical, immunophenotypic, or genetic characteristics. Our results demonstrate that on-going somatic hypermutation is a prominent feature of splenic marginal zone lymphoma with circulating villous lymphocytes. On-going somatic hypermutation has previously been demonstrated in extra-nodal and nodal marginal zone lymphoma. Our results indicate that marginal zone lymphomas at different anatomical localizations may derive from a similar B-cell subset.

Primary marginal zone B-cell lymphoma of the lymph node resembling plasmacytoma arising from a plasma cell variant of Castleman's disease. A clinicopathological and immunohistochemical study of seven patients

Nodal marginal zone B-cell lymphomas (NMZBL) occasionally represent prominent plasma cell differentiation. Recently, we presented a patient with NMZBL who exhibited histological features that resembled plasmacytoma arising from a localized plasma cell variant of Castleman's disease. To further clarify the clinicopathological, immunohistochemical, and genotypical findings, we studied seven such patients. Clinically, these patients were characterized by localized disease and an indolent clinical course with a slowly growing bulky mass in the affected lymph node. Only one patient exhibited paraproteinemia. Histologically, the lesions were characterized by numerous evenly distributed germinal centers in extensive sheets of plasma cells. Various numbers of centrocyte-like (CCL) cells arranged in a marginal zone distribution pattern occupied the peripheral region of the lymph node. The majority of the lymphoid follicles had atrophic or regressive germinal centers. A few lymphoid follicles were colonized by CCL cells. Immunohistochemistry showed that all of the lesions contained a monoclonal plasma cell population. In three tumors, a number of the CCL cells had a similar light chain restriction pattern to that observed in plasma cells. Two of the four patients evaluated exhibited clonal bands for the IgH gene by polymerase chain reaction assay. Moreover, the presence of surface IgM+, IgD- and CD27+ CCL- cells suggests that these tumors are derived from memory B-lymphocytes.

Follicular lymphoma without t(14;18) and with BCL-6 rearrangement: a lymphoma subtype with distinct pathological, molecular and clinical characteristics

Translocations involving the BCL-6 gene are frequently observed in diffuse large B cell lymphoma, but have rarely been reported in follicular lymphoma (FL). We studied a distinct cohort of FLs with a 3q27/BCL-6 gene rearrangement, but lacking the t(14;18) translocation. In 13/15 cases, translocations involved the 3q27 and the 14q32 regions. All cases displayed a marked follicular growth pattern and, in some instances, a monocytoid component. Tumor cells were CD5(-) CD20(+) CD23(-) CD43(-) BCL-6(+), and in the main CD10 negative (n = 10, 71%) and BCL-2 negative (n = 11, 78%). When compared to 20 typical t(14;18)(+) FLs, the presence of large follicles (P = 0.01) and a CD10(-)/BCL-2(-) phenotype were more frequently observed (P = 0.001) in our cohort. Clonal mutations arising in the BCL-6 first intron were observed in 5/7 cases with evidence of intraclonal heterogeneity, consistent with a germinal center origin. No significant difference was found in comparison to t(14;18)(+) FL regarding age, sex, performance status, bone marrow involvement or overall survival. However, in the 3q27(+) FL group, a stage III/IV disease and a bulky mass were less frequently observed. This study indicates that 3q27(+) FL without t(14;18) translocation have peculiar clinico-pathologic features and may correspond to a rare and distinct subtype of lymphoma originating from the germinal center.