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

A rare case of B-lymphoproliferative disorder with villous lymphocytes harboring t(8;14)(q24;q32) translocation

Splenic lymphoma with villous lymphocytes (SLVL) or splenic marginal zone lymphoma with circulating villous lymphocytes is rare, and prolymphocytic transformation of SLVL is rarer. At present, only one case of SLVL with t(8;14)(q24;q32) translocation has been reported. In this study, we report a case of B-lymphoproliferative disorder with villous lymphocytes harboring t(8;14)(q24;q32) chromosome translocation that we inclined to SLVL with a prolymphocytic transformation. A 73-year-old female showed marked hepatosplenomegaly and high lymphocytosis (lymphocytes > 200 × 10⁹/L). The abnormal lymphocytes had short coarse villi and round nuclei with prominent nucleoli. The immunophenotypes showed CD19⁺, CD20⁺, HLA-DR⁺, CD22⁺, CD5⁺, Kappa⁺, CD25^dim, CD71^dim, Lambda^-, CD7^-, CD10^-, CD23^-, CD34^-, CD33^-, CD13^-, CD14^-, CD117^-, CD64^-, CD103^-, and CD11c^-. The karyotype showed complex abnormality: 46XX,+ 3,-10, t(8;14)(q24; q32)[11]/46XX[9]. The cytoplasmic projection, immunological characteristics, and trisomy 3 chromosome abnormality supported the diagnosis of SLVL. However, the presence of prominent nucleoli and high lymphocytosis suggested prolymphocytic transformation, probably as a result of t(8,14) chromosome translocation. In this report, we described an unusual case of B-lymphoproliferative disorder with villous lymphocytes harboring t(8;14)(q24;q32) translocation, which could provide help in the diagnosis and differential diagnosis of B-lymphocytic proliferative diseases.

Splenic marginal zone lymphoma: from genetics to management

Splenic marginal zone lymphoma (SMZL) is a rare B-cell malignancy involving the spleen, bone marrow, and frequently the blood. SMZL lymphomagenesis involves antigen and/or superantigen stimulation and molecular deregulation of genes (NOTCH2 and KLF2) involved in the physiological differentiation of spleen marginal zone B cells. Diagnosis requires either spleen histology or, alternatively, the documentation of a typical cell morphology and immunophenotype on blood cells coupled with the detection of intrasinusoidal infiltration by CD20+ cells in the bone marrow. Among B-cell tumors, deletion of 7q and NOTCH2 mutations are almost specific lesions of SMZL, thus representing promising diagnostic biomarkers of this lymphoma. Although the majority of SMZLs show an indolent course with a median survival of approximately 10 years, nearly 30% of patients experience a poor outcome. No randomized trials are reported for SMZL, and few prospective trials are available. A watch-and-wait approach is advisable for asymptomatic patients. Treatment options for symptomatic patients ranges from splenectomy to rituximab alone or combined with chemotherapy. In some geographic areas, a subset of patients with SMZL associates with hepatitis C virus infection, prompting virus eradication as an effective lymphoma treatment. It would be worthwhile to explore deregulated cellular programs of SMZL as therapeutic targets in the future; improved clinical and biological prognostication will be essential for identifying patients who may benefit from novel approaches.

An Immunogenetic Signature of Ongoing Antigen Interactions in Splenic Marginal Zone Lymphoma Expressing IGHV1-2*04 Receptors

PURPOSE

Prompted by the extensive biases in the immunoglobulin (IG) gene repertoire of splenic marginal-zone lymphoma (SMZL), supporting antigen selection in SMZL ontogeny, we sought to investigate whether antigen involvement is also relevant post-transformation.

EXPERIMENTAL DESIGN

We conducted a large-scale subcloning study of the IG rearrangements of 40 SMZL cases aimed at assessing intraclonal diversification (ID) due to ongoing somatic hypermutation (SHM).

RESULTS

ID was identified in 17 of 21 (81%) rearrangements using the immunoglobulin heavy variable (IGHV)1-2*04 gene versus 8 of 19 (40%) rearrangements utilizing other IGHV genes (P= 0.001). ID was also evident in most analyzed IG light chain gene rearrangements, albeit was more limited compared with IG heavy chains. Identical sequence changes were shared by subclones from different patients utilizing the IGHV1-2*04 gene, confirming restricted ongoing SHM profiles. Non-IGHV1-2*04 cases displayed both a lower number of ongoing SHMs and a lack of shared mutations (per group of cases utilizing the same IGHV gene).

CONCLUSIONS

These findings support ongoing antigen involvement in a sizable portion of SMZL and further argue that IGHV1-2*04 SMZL may represent a distinct molecular subtype of the disease.

[Molecular analysis of immunoglobulin genes in the tumor B cells in splenic marginal zone lymphoma]

AIM

To determine the immunoglobulin variable heavy chain (gVH) genes and their somatic mutations and to compare these data with the clinical and laboratory parameters of patients and the outcomes of the disease.

SUBJECTS AND METHODS

The investigation enrolled 24 patients (9 men and 15 women whose age was 32 to 77 years (median age, 60 years) with splenic marginal zone B-cell lymphoma (SMZBCL). The latter was diagnosed on the basis of histological and immunohistochemical examinations of a bone marrow trephine biopsy specimen, immunophenotyping of peripheral lymphoid cells or bone marrow aspirates.

RESULTS

The mutational status of the IgVH genes was analyzed in all the 24 patients. It was found that the tumor cells contained mutated IgVH genes (the VH1-family genes participated in most cases) in 15 (62.5%) patients with SMZBCL and unmutated ones in 9 (37.5%). There was a tendency towards more common tumor progression in patients with unmutated IgVH genes than in those with mutated ones.

CONCLUSION

The presence of SMZBCL cases with both mutated and unmutated IgVH genes and the higher frequency of the VH1-2 gene are likely to indicate the molecular heterogeneity of the origin of this lymphoma.

Splenic marginal-zone lymphoma: ontogeny and genetics

Splenic marginal-zone lymphoma (SMZL) is a rare tumor that has recently emerged as a prototype for how the interplay between genetics and environment shapes the natural history of lymphomas. Indeed, the recent identification of molecular immunogenetic subgroups within SMZL may prove to be relevant not only for the sub-classification of the disease but also for improved understanding of the underlying biology. In contrast to other B-cell lymphomas, SMZL lacks a characteristic genetic lesion, although the majority of cases harbor genomic aberrations, as recently revealed by high-throughput studies that identified recurrent genetic aberrations, several in pathways related to marginal-zone differentiation and B-cell signaling. Here we provide an overview of recent research into the molecular and cellular biology of SMZL and related disorders, with special emphasis on immunogenetics and genomic aberrations, and discuss the value of molecular and cellular markers for the diagnosis and differential diagnosis of these entities.

Splenic marginal zone lymphoma: disease features and management

Splenic marginal zone lymphoma (SMZL) is a lymphoma recognized as a distinct entity in the WHO classification of the lymphoid tumors. SMZL probably results from the expansion of a marginal zone B-cell driven by persistent antigen stimulation. SMZL is clinically and biologically heterogeneous. The SMZL Working Group has published guidelines for the diagnosis, workup and treatment of SMZL. There are no standard criteria to initiate treatment. A policy of watch and wait in asymptomatic patients is recommended. In symptomatic patients, data from retrospective studies suggest that rituximab with or without chemotherapy is the best strategy for SMZL. It is uncertain which is the optimal type of chemotherapy and whether patients may benefit from splenectomy prior chemoimmunotherapy. In the future, we may see progress with agents targeting known molecular lesions in SMZL.

The prognostic impact of clinical and molecular features in hairy cell leukaemia variant and splenic marginal zone lymphoma

Hairy cell leukaemia variant (HCL-variant) and splenic marginal zone lymphoma (SMZL) are disorders with overlapping features. We investigated the prognostic impact in these disorders of clinical and molecular features including IGH VDJ rearrangements, IGHV gene usage and TP 53 mutations. Clinical and laboratory data were collected before therapy from 35 HCL-variant and 68 SMZL cases. End-points were the need for treatment and overall survival. 97% of HCL-variant and 77% of SMZL cases required treatment (P = 0·009). Survival at 5 years was significantly worse in HCL-variant [57% (95% confidence interval 38-73%)] compared with SMZL [84% (71-91%); Hazard Ratio 2·25 (1·20-4·25), P = 0·01]. In HCL-variant, adverse prognostic factors for survival were older age (P = 0·04), anaemia (P = 0·01) and TP 53 mutations (P = 0·02). In SMZL, splenomegaly, anaemia and IGHV genes with >98% homology to the germline predicted the need for treatment; older age, anaemia and IGHV unmutated genes (100% homology) predicted shorter survival. IGHV gene usage had no impact on clinical outcome in either disease. The combination of unfavourable factors allowed patients to be stratified into risk groups with significant differences in survival. Although HCL-variant and SMZL share some features, they have different outcomes, influenced by clinical and biological factors.

Over 30% of patients with splenic marginal zone lymphoma express the same immunoglobulin heavy variable gene: ontogenetic implications

We performed an immunogenetic analysis of 345 IGHV-IGHD-IGHJ rearrangements from 337 cases with primary splenic small B-cell lymphomas of marginal-zone origin. Three immunoglobulin (IG) heavy variable (IGHV) genes accounted for 45.8% of the cases (IGHV1-2, 24.9%; IGHV4-34, 12.8%; IGHV3-23, 8.1%). Particularly for the IGHV1-2 gene, strong biases were evident regarding utilization of different alleles, with 79/86 rearrangements (92%) using allele (*)04. Among cases more stringently classified as splenic marginal-zone lymphoma (SMZL) thanks to the availability of splenic histopathological specimens, the frequency of IGHV1-2(*)04 peaked at 31%. The IGHV1-2(*)04 rearrangements carried significantly longer complementarity-determining region-3 (CDR3) than all other cases and showed biased IGHD gene usage, leading to CDR3s with common motifs. The great majority of analyzed rearrangements (299/345, 86.7%) carried IGHV genes with some impact of somatic hypermutation, from minimal to pronounced. Noticeably, 75/79 (95%) IGHV1-2(*)04 rearrangements were mutated; however, they mostly (56/75 cases; 74.6%) carried few mutations (97-99.9% germline identity) of conservative nature and restricted distribution. These distinctive features of the IG receptors indicate selection by (super)antigenic element(s) in the pathogenesis of SMZL. Furthermore, they raise the possibility that certain SMZL subtypes could derive from progenitor populations adapted to particular antigenic challenges through selection of VH domain specificities, in particular the IGHV1-2(*)04 allele.

Splenic marginal zone lymphoma with VH1-02 gene rearrangement expresses poly- and self-reactive antibodies with similar reactivity

One-third of all splenic marginal zone lymphomas (SMZL) use the IgH VH1-02 gene. These cases are usually not associated with hepatitis C virus infection. Of interest, the rearranged VH1-02 genes display similar complementarity determining regions 3, a finding confirmed by our study. The latter suggests that these SMZL may produce antibodies with similar reactivity. We produced recombinant antibodies from 5 SMZL cases with VH1-02 gene rearrangement to study the binding reactivity of these antibodies. Surprisingly, the recombinant antibodies demonstrated poly- and self-reactivity as demonstrated by their reactivity with nuclear, cytoplasmic, as well as membranous antigens expressed by human cells and by reactivity with human serum. This polyreactivity was specific as demonstrated by ELISA. The antibodies did not react with proteins on the cell surface that are induced by apoptosis as shown for antibodies produced by chronic lymphatic leukemia with VH1-02 gene rearrangement. The results indicate that a common subset of SMZL arises from polyreactive B cells, a subset of marginal zone B cells that are important in the immunologic defense against infection.

Hairy-cell leukemia variant: recent view on diagnosis, biology and treatment

Hairy-cell leukemia variant (HCl-V) is a district clinico-pathological entity with intermediate features between classical HCl (HCl-C) and B-cell prolymphocytic leukemia. HCl-V is now included in the World Health Organization (WHO) classification as a provisional entity. It is an uncommon disorder accounting for approximately 0.4% of chronic lymphoid malignancies and 10% of all HCl cases. In contrast to HCl-C, HCl-V is a more aggressive disease and according to the new WHO classification it is no longer considered to be biologically related to HCl-C. Patients with HCl-V have an elevated white blood count, easy-to-aspirate bone marrow and weak reactivity to tartrate - resistant acid phosphatase (TRAP). Immunophenotypically, HCl-V cells are positive for CD103 and CD11c and negative for CD25. The HCl-V cells express also the B-cell antigens, CD19, CD20 and CD22. The HCl-V patients have frequently an unmutated Ig gene configuration. Currently, the principles of therapy for this rare disease derive from uncontrolled single institutional studies, or even single case reports. In contrast to HCl-C, the HCl-V response to purine nucleoside analogs (PNA) is limited to partial responses in approximately 50% of patients. However, complete responses were observed in patients treated with rituximab and anti-CD22 immunotoxins. In Japan, a distinct subtype of HCl known as HCl-Japanese variant (HCl-JV) has been identified. As with HCl-V, patients with HCl-JV have leukocytosis, weak TRAP activity in leukemic cells, and lack of CD25 antigen. In this review, the biology, diagnostic criteria, and current therapeutic options in HCl-V and HCl-JV are presented.

Identification of uniquely expressed transcription factors in highly purified B-cell lymphoma samples

Transcription factors (TFs) are critical for B-cell differentiation, affecting gene expression both by repression and transcriptional activation. Still, this information is not used for classification of B-cell lymphomas (BCLs). Traditionally, BCLs are diagnosed based on a phenotypic resemblance to normal B-cells; assessed by immunohistochemistry or flow cytometry, by using a handful of phenotypic markers. In the last decade, diagnostic and prognostic evaluation has been facilitated by global gene expression profiling (GEP), providing a new powerful means for the classification, prediction of survival, and response to treatment of lymphomas. However, most GEP studies have typically been performed on whole tissue samples, containing varying degrees of tumor cell content, which results in uncertainties in data analysis. In this study, global GEP analyses were performed on highly purified, flow-cytometry sorted tumor-cells from eight subgroups of BCLs. This enabled identification of TFs that can be uniquely associated to the tumor cells of chronic lymphocytic leukemia (CLL), diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), hairy cell leukemia (HCL), and mantle cell lymphoma (MCL). The identified transcription factors influence both the global and specific gene expression of the BCLs and have possible implications for diagnosis and treatment.

Stereotyped patterns of B-cell receptor in splenic marginal zone lymphoma

Antigen stimulation may be important for splenic marginal zone lymphoma pathogenesis. To address this hypothesis, the occurrence of stereotyped B-cell receptors was investigated in 133 SMZL (26 HCV+) compared with 4,414 HCDR3 sequences from public databases. Sixteen SMZL (12%) showed stereotyped BCR; 7 of 86 (8%) SMZL sequences retrieved from public databases also belonged to stereotyped HCDR3 subsets. Three categories of subsets were identified: i) "SMZL-specific subsets" (n=5), composed only of 12 SMZL (9 HCV-from our series); ii) "Non-Hodgkin's lymphoma-like subsets" (n=5), comprising 5 SMZL (4 from our series) clustering with other indolent lymphomas; iii) "CLL-like subsets" (n=6), comprising 6 SMZL (3 from our series) that belonged to known CLL subsets (n=4) or clustered with public CLL sequences. Immunoglobulin 3D modeling of 3 subsets revealed similarities in antigen binding regions not limited to HCDR3. Overall, data suggest that the pathogenesis of splenic marginal zone lymphoma may involve also HCV-unrelated epitopes or an antigenic trigger common to other indolent lymphomas.

Splenic marginal zone lymphoma: Clinical clustering of immunoglobulin heavy chain repertoires

Immunoglobulin gene usage and somatic mutation patterns were studied in 59 patients with splenic marginal zone lymphoma and were correlated with clinical characteristics. Fifty-nine IGHV rearrangements were amplified. IGHV1, IGHV3, and IGHV4 subgroups accounted for 30%, 56%, and 14% of sequences, respectively. IGHV genes most frequently used were IGHV1-2 (n=12), IGHV3-23 (n=15), IGHV3-30 (n=7) and IGHV4-34 (n=5). IGHV was unmutated in 25%. Villous lymphocytes >10% were detected in 50% of patients belonging to the IGHV1-2 group, in 21% of the IGHV3-23 group, and in no patient of the IGHV3-30 group (p=0.05). Liver involvement was present in 50% of the IGHV3-30 group, in 9% of the IGHV3-23 group, and in no patient of the IGHV1-2 group (p=0.04). HCV-serology was positive in 50% of the IGHV3-30 group, in 7% of the IGHV3-23 group, and in 17% of the IGHV1-2 group (p=0.04). The proportion of intermediate and high risk patients according to the SMZL score was higher in the unmutated respect to the mutated group (69% vs 32%, p=0.05). In conclusion, IGHV rearrangement analysis in splenic marginal zone B-cell lymphoma reveals a non-random preference for use of IGHV1-2, IGHV3-23 and IGHV3-30 genes, whose presence differs according to clinical features and prognostic category.

Pathophysiological aspects of memory B-cell development

B cells follow two functionally distinct pathways of development: a classical germinal center (GC) T-dependent pathway in which diversification and maturation generate a slow, but virtually unlimited high-affinity response to cognate antigens; and a marginal zone (MZ) T-independent pathway providing a first line of 'innate-like' defense against specific pathogens. Cells populating these two distinct locations are the normal counterparts of two clinically important pathological entities, follicular lymphoma (FL) and MZ lymphoma (MZL). FL and MZ represent paradigms of two rising concepts of lymphomagenesis, protracted preclinical and antigen-driven lymphoproliferation, respectively. Integrating the mechanisms and functions of MZ and GC B cells and the distinctive features of their pathological counterparts should provide essential clues to the understanding of their malignant development, and should offer new insights into the design of effective treatments for B-cell lymphomas.

Junctional adhesion molecule C (JAM-C) distinguishes CD27+ germinal center B lymphocytes from non-germinal center cells and constitutes a new diagnostic tool for B-cell malignancies

Differentiation of naïve B cells into plasma cells or memory cells occurs in the germinal centers (GCs) of lymph follicles or alternatively via a GC- and T-cell-independent pathway. It is currently assumed that B-cell lymphomas correlate to normal B-cell differentiation stages, but the precise correlation of several B-cell lymphomas to these two pathways remains controversial. In the present report, we describe the junctional adhesion molecule C (JAM-C), currently identified at the cell-cell border of endothelial cells, as a new B-cell marker with a tightly regulated expression during B-cell differentiation. Expression of JAM-C in tonsils allows distinction between two CD27+ B-cell subpopulations: JAM-C- GC B cells and JAM-C+ non-germinal B cells. The expression of JAM-C in different B-cell lymphomas reveals a disease-specific pattern and allows a clear distinction between JAM-C- lymphoproliferative syndromes (chronic lymphocytic leukemia, mantle cell lymphoma and follicular lymphoma) and JAM-C+ ones (hairy cell leukemia, marginal zone B-cell lymphoma). Therefore, we propose JAM-C as a new identification tool in B-cell lymphoma diagnosis.

Splenic Marginal-zone Lymphoma: One or More Entities? A Histologic, Immunohistochemical, and Molecular Study of 42 Cases

We analyzed 42 splenic marginal-zone lymphoma (SMZL) cases diagnosed on splenectomy specimens after established World Health Organization criteria. A predominantly nodular growth pattern was observed in 24 cases; the remainder showed predominantly (11/42) or exclusively (7/42) diffuse infiltration. Twenty-one cases showed the "classic" biphasic appearance; 13 cases exhibited marginal-zone morphology; finally, 8 cases were composed predominantly of small cells. CD21 and CD35 were expressed by 12/42 and 17/38 cases, respectively. DBA.44 was detected in 24/42 cases. Seventeen of 37 cases were surface IgD (SIgD)-positive. Twenty-one of 22 analyzed cases were SIgM-positive (12/21 coexpressed SIgD). Five of 37 cases were SIgG-positive. CD27 staining was observed in 21/35 cases; 7/18 CD27-positive cases coexpressed SIgD; 7/14 CD27-negative cases were SIgD-positive. Forty IGHV-D-J rearrangements were amplified in 34/42 cases: the IGHV4-34 gene predominated, followed by IGHV1-2. Using the 98% homology cut-off, 25/40 (62.5%) IGHV sequences were considered as "mutated": 10/11 cases with monomorphous, marginal-zone morphology were IGHV-mutated; in contrast, 4/6 cases with monomorphous, small-cell morphology were IGHV-unmutated. Five of 7 cases expressing IGHV1 subgroup genes had biphasic morphology, whereas 6/9 IGHV3-expressing cases had monomorphous, marginal-zone morphology. Most IGHV-mutated cases (14/20; 70%) were SIgD-negative; in contrast, 8/11 IGHV-unmutated cases expressed SIgD. CD27 was detected in 10/17 IGHV-mutated and 6/10 IGHV-unmutated cases. Seven of 11 CD27-negative cases were IGHV-mutated; 5/7 CD27-negative/IGHV-mutated cases expressed DBA.44. These results confirm the considerable histologic, immunohistochemical, and molecular heterogeneity of SMZL and indicate an origin from the diverse resident B-cell populations of the normal SMZ.

Somatic hypermutation and VH gene usage in hairy cell leukaemia

To examine the usage and mutational status of VH genes in hairy cell leukaemia (HCL), we analysed 24 immunoglobulin heavy chain (IgH) sequences expressed in 23 patients. None had premature stop codons. VH3-23 was the most common gene and a VH6 gene was observed for the first time in HCL. Although the mean mutation frequency was 6.1%, slightly higher than in previous HCL series, four patients had 99.6-100% homology to germline sequences, three of whom had high tumour burdens and poor outcomes. Despite the high mutation frequency, only two of 24 rearrangements had clear statistical evidence of antigen-dependent somatic mutation. Our results increase the database of reported functional HCL rearrangements to 94 in 92 patients. Overall, both gene usage and mutation frequency are very similar to mucosa-associated lymphoid tissue-type marginal zone lymphoma. The data are consistent with HCL originating from post-germinal centre marginal zone B cells, although the heterogeneity observed suggests that HCL may originate differently in some patients, and this could have implications for prognosis and treatment.

Immunoglobulin heavy- and light-chain repertoire in splenic marginal zone lymphoma

The considerable heterogeneity in morphology, immunophenotype, genotype, and clinical behavior of splenic marginal zone lymphoma (SMZL) hinders firm conclusions on the origin and differentiation stage of the neoplastic cells. Immunoglobulin (IG) gene usage and somatic mutation patterns were studied in a series of 43 SMZL cases. Clonal IGHV-D-J rearrangements were amplified in 42/43 cases (4 cases carried double rearrangements). Among IGHV-D-J rearrangements, IGHV3 and IGHV4 subgroup genes were used with the highest frequency. Nineteen IGHV genes were unmutated (> 98% homology to the closest germline IGHV gene), whereas 27/46 were mutated. Clonal IGKV-J and IGLV-J gene rearrangements were amplified in 36/43 cases, including 31 IGKV-J (8/31 in lambda light-chain expressing cases) and 12 IGLV-J rearrangements; 9/31 IGKV and 6/12 IGLV sequences were mutated. IGKV-J and IGLV-J rearrangements used 14 IGKV and 9 IGLV different germline genes. Significant evidence for positive selection by classical T-dependent antigen was found in only 5/27 IGHV and 6/15 IGKV+IGLV mutated genes. These results provide evidence for the diverse B-cell subpopulations residing in the SMZ, which could represent physiologic equivalents of distinct SMZL subtypes. Furthermore, they indicate that in SMZL, as in other B cell malignancies, a complementarity imprint of antigen selection might be witnessed either by IGHV, IGKV, or IGLV rearranged sequences.

Constitutive expression of the AP-1 transcription factors c-jun, junD, junB, and c-fos and the marginal zone B-cell transcription factor Notch2 in splenic marginal zone lymphoma

Splenic marginal zone lymphoma (SMZL) is a lymphoma type of putative marginal zone B-cell origin. No specific genetic alterations have yet been demonstrated in SMZL. Clinically, SMZL is a low-grade B-cell non-Hodgkin lymphoma. However, the presence of p53 mutation, 7q22-7q32 deletion or the absence of somatic hypermutations of immunoglobulin genes has been correlated with a worse prognosis. In this study, we analyzed genome-wide gene expression of 24 cases of SMZL using the microarray technique. The AP-1 transcription factors c-jun, junD, junB, and c-fos as well as Notch2 were found to be specifically up-regulated. These data were confirmed by real-time PCR and immunohistochemical staining of tissue sections. The absence of concordant high expression of the MAP kinases, the signaling cascade leading to AP-1 up-regulation, suggests autoregulation of the AP-1 transcription factors and an important role in SMZL oncogenesis. High expression of Notch2, a transcription factor that induces marginal zone B-cell differentiation, is highly suggestive for a marginal zone B-cell origin of SMZL. In addition, SMZL with the 7q deletion showed high expression of TGF-beta1 and low expression of the DNA helicase XPB, a crucial part of the nucleotide excision repair complex, possibly explaining the more aggressive clinical course of those cases.

The immunoglobulin genes and chronic lymphocytic leukemia (CLL)

The somatic hypermutation (SMH) status of the immunoglobulin (Ig) V(H) genes can divide chronic lymphocytic leukemia (CLL) into two prognostic subsets, with mutated V(H) genes display superior survival compared to unmutated cases. Biased V(H) gene usage has also been reported in CLL which may reflect antigen selection. In a V(H) gene analysis of 265 CLL cases we confirmed the prognostic impact of the V(H) mutation status and found preferential V(H) gene usage in both the mutated and unmutated subset. Interestingly, CLL cases rearranging one particular V(H) gene, V(H)3-21, displayed poor outcome despite that two-thirds showed mutated V(H) genes. Many of the V(H)3-21 utilizing cases expressed lambda light chains, rearranged a Vlambda2-14 gene, and had homologous complementarity determining region 3s (CDR3s), implying recognition of a common antigen epitope. We thus believe that the cases rearranging the V(H)3-21 gene comprises an additional CLL entity. We further analyzed the V(H) gene rearrangements and, specifically, the heavy chain CDR3 sequences in 346 CLL cases to investigate the role of antigens in CLL. We identified six new subgroups with similar HCDR3 features and restricted VL gene usage as in the V(H)3-21-using group. Our data indicate a limited number of antigen recognition sites in these subgroups and give further evidence for antigen selection in the development of CLL. Different mutational cutoffs have been used to distinguish mutated CLL in addition to the 2% cutoff. Using three levels of somatic mutations we divided 323 CLLs into subsets with divergent survival (<2%, 2-5% and >5% mutations). This division revealed a low-mutated subgroup (2-5%) with inferior outcome that would have been masked using the traditional 2% cutoff. A 1513A/C polymorphism in the P2X(7) receptor gene was reported to be more frequent in CLL, but no difference in genotype frequencies was revealed in our 170 CLL cases and 200 controls. However, CLL cases with the 1513AC genotype showed superior survival than 1513AA cases and this was in particular confined to CLL with mutated VH genes. In summary, we could define new prognostic subgroups in CLL using Ig gene rearrangement analysis. This also allowed us to gain insights in the biology and potential role of antigen involvement in the pathogenesis of CLL.

Splenic marginal zone lymphoma

Splenic marginal zone lymphoma (SMZL) is an indolent B cell malignancy usually involving spleen, bone marrow and blood. The disease presents as an incidental finding or with symptoms of splenic enlargement or anaemia. Diagnosis is based on a combination of lymphocyte morphology, immunophenotype and marrow and /or splenic histology. There is no genetic abnormality specific for SMZL, but deletions of chromosome 7q are the commonest abnormality and are found in 30-50% of cases. SMZL cells may have either mutated or unmutated immunoglobulin variable region genes and probably arise from different subsets of splenic marginal zone B cells. Prognostic factors are poorly defined and only loss or mutation of the p53 gene is consistently associated with a poor outcome. Therapeutic options include splenectomy, splenic irradiation, alkylating agents, purine analogues or anti CD20 antibody. The median survival is 10-13 years and most disease-related deaths are associated with transformation to diffuse large cell lymphoma.

Clonally related splenic marginal zone lymphoma and Hodgkin lymphoma with unmutated V gene rearrangements and a 15-yr time gap between diagnoses

Hodgkin lymphoma (HL) can rarely occur during the course of B-cell non-Hodgkin lymphoma (B-NHL), where both the HL and NHL tumours have been reported to be clonally related in most of the few combination lymphomas so far investigated. We here investigated a case that developed HL 15 yr after being diagnosed with an indolent B-cell lymphoma, classified as a splenic marginal zone lymphoma (SMZL). Analysis of rearranged immunoglobulin genes in the SMZL clone and in single Hodgkin Reed-Sternberg cells revealed presence of identical V gene rearrangements, thus demonstrating a clonal relationship. In contrast to previously described B-NHL/HL combinations, in this case both types of tumour cells carried unmutated V gene rearrangements. We conclude that the HL evolved from an unmutated tumour precursor, either the SMZL clone itself or a common earlier precursor.

CD27 distinguishes two phases in bone marrow infiltration of splenic marginal zone lymphoma

AIMS

To investigate CD27 expression in splenic marginal zone lymphoma (SMZL), an indolent low-grade B-cell lymphoma with constant involvement of the bone marrow, especially with an intrasinusoidal pattern. It is not clear if the neoplastic clone is composed of virgin or somatically mutated B cells. CD27 is reported to be a hallmark of memory B cells.

METHODS AND RESULTS

We evaluated 64 bone marrow biopsy specimens (BMBs) from 36 patients with SMZL for the expression of CD27. For comparison, splenectomy specimens of patients with traumatic splenic rupture or with SMZL were used. All BMBs showed lymphomatous infiltration. When located in the marrow sinusoids, neoplastic cells were CD27- in all cases and therefore corresponded to naive B cells. In nodular/interstitial infiltration, the cells were CD27+ and therefore corresponded to memory B cells. No difference in immunohistochemical expression of B and T antibodies was found between intrasinusoidal and interstitial/nodular infiltration. CD27 was constantly expressed in the splenic marginal zone of normal spleen, surgically removed for trauma, and in seven out of 10 spleens with SMZL.

CONCLUSION

We propose the existence of two different phases of neoplastic progression with, first, expansion of a virgin B clone in the bone marrow and, following exposure to antigen, a re-colonization of the bone marrow.