Splenic marginal zone cell lymphoma. An immunophenotypic and molecular study of five cases

Splenic marginal zone lymphomas are characterized by loss of interstitial regions of chromosome 7q, 7q31.32 and 7q36.2 that include the protection of telomere 1 (POT1) and sonic hedgehog (SHH) genes

To further characterize the genotypic features of splenic (S) and nodal (N) marginal zone lymphomas (MZL) we compared eight SMZL and five NMZL by array-based comparative genomic hybridization (aCGH). Arbitrarily, aberrations were divided into major imbalances, defined as gains or losses involving five or more contiguous genetic loci, and minor imbalances, defined as those involving four or fewer loci. SMZL, but not NMZL, demonstrated major imbalances. These included deletions involving various lengths of 7q (three cases), and 14q23q24 (one case) and gains of 9p13p21 (one case), 13q21q33 (one case) and 16p13.1 (one case). Common minor imbalances in SMZL were: loss of sonic hedgehog gene (SHH) at 7q36.2 (four cases), loss of protection of telomere 1 gene (POT1) at 7q31.32 (three cases), and gain of glioma associated oncogene 1 (GLI1) at 12q13.2 (three cases). Common minor alterations in NMZL were: loss of the fas-associated via death domain gene (FADD) at 11q13.2 (three cases) and gain of GLI1 (five cases). In conclusion, SMZL, but not NMZL, demonstrates large genomic imbalances and frequent loss of the 7q31.32 and 7q36.2 regions involving POT1 and SHH, respectively. In NMZL, loss of FADD and gain of GLI1 are frequent events.

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.

Immunophenotypic and Cytogenetic Comparison of Waldenström's Macroglobulinemia with Splenic Marginal Zone Lymphoma

Some B-cell lymphoproliferative disorders displaying a serum monoclonal immunoglobulin (Ig) M protein could be difficult to differentiate from Waldenstrom's macroglobulinemia (WM). We report on the immunophenotypic and cytogenetic characteristics of 85 patients with WM and compare them with 29 patients with splenic marginal zone lymphoma (SMZL). For immunophenotyping, WM and SMZL constantly expressed panB-cell markers (CD19, CD20, CD22, and surface Ig). However, there were differences in the k/l ratio (1.2:1 for SMZL and 4.5:1 for WM) and in some markers such as CD22 and CD11c, which were overexpressed in patients with SMZL compared with patients with WM, whereas CD25 was more frequently positive in WM (88% vs. 44%). The CD103 antigen was always negative in WM, whereas it was positive in 40% of SMZL cases. The monoclonal antibody FMC7 was usually positive in both entities: heterogeneous in WM but homogeneous in SMZL. The combination of CD25 and CD22 could differentiate between WM and SMZL. The principal molecular abnormality in WM is 6q deletion (30% in our experience), whereas in SMZL the most common abnormalities are loss of 7q (19%) along with +3q (19%) and +5q (10%). Interestingly, the incidence of IgH rearrangement was low in WM (12%) and SMZL (10%). Immunophenotypic and molecular cytogenetic studies could help to distinguish WM from SMZL.

Splenic marginal zone lymphoma

Splenic marginal zone lymphoma (SMZL) is an indolent lymphoproliferative disease accounting for approximately 1% of all lymphomas. SMZL presents with marked splenomegaly, and often accompanied by circulating atypical 'villous lymphocytes' and is also known as splenic lymphoma with villous lymphocytes. Histologically, the spleen in SMZL is characterised by a nodular infiltrate based on pre-existing white pulp but also involving the red pulp. Within the white pulp, the infiltrate has a biphasic morphology comprising an inner zone of small lymphocytes and a peripheral (marginal) zone of larger lymphoid cells. Usually the splenic lymph nodes and bone marrow are also involved by a vaguely nodular infiltrate of similar nature. Immunophenotypically, the tumor cells has a mature B-cell phenotype and frequently express IgM and IgD but typically lack CD5, CD23, CD43, CD10, Bcl-6 and cyclin D1. Analysis of immunoglobulin heavy-chain gene variable regions suggest that some cases of SMZL arise form postfollicular B cells but others from naïve B cells. Genetic studies have shown abnormalities of a number of chromosomes however 7q31-32 allelic loss appears to be characteristic. Histological differential diagnosis include a number of entities such as lymphoid hyperplasias, other marginal zone lymphomas, mantle cell lymphoma, follicular lymphoma, and B-CLL.

Splenic marginal zone lymphoma

Splenic marginal zone lymphoma (SMZL) is a specific low-grade small B-cell lymphoma that is incorporated in the World Health Organization classification. Characteristic features are splenomegaly, moderate lymphocytosis with villous morphology, intrasinusoidal pattern of involvement of various organs, especially bone marrow, and relative indolent course. Tumor progression with increase of blastic forms and aggressive behavior are observed in a minority of patients. Molecular and cytogenetic studies have shown heterogeneous results probably because of the lack of standardized diagnostic criteria. To date, no definitive therapy has been established. Therapeutic options include treatment abstention, splenectomy, splenic irradiation, and chemotherapy.

Splenic small B-cell lymphoma with predominant red pulp involvement: a diffuse variant of splenic marginal zone lymphoma?

AIMS

Splenic marginal zone lymphoma (SMZL) has been characterized by a micronodular pattern of infiltration, biphasic cytology, follicular replacement and the presence of marginal zone differentiation. Here we describe four cases with some distinctive features, such as diffuse splenic infiltration, lack of micronodules, marginal zone cytology, p53 inactivation and cutaneous involvement.

METHODS AND RESULTS

In the course of a review of cases of SMZL, we recognized the existence of a subset of four cases of splenic B-cell lymphoma, with predominantly red pulp involvement, absence of follicular replacement, and a monomorphous population of tumoral cells resembling marginal zone B-cells, with scattered nucleolated blast cells. The immunophenotype (bcl2+, CD5-, CD10-, CD43-, CD23-, cyclin D1-, IgD- (3/4)) was consistent with SMZL. Bone marrow infiltration (4/4) and peripheral blood involvement (2/4) showed similar findings to those described for SMZL in these locations. However, unlike classical SMZL, 2/4 had cutaneous involvement, and 4/4 cases showed either p53 mutation or anomalous p53 staining (p53+, p21-). CONCLUSIONS; In spite of a diffuse pattern of splenic infiltration, cutaneous involvement and p53 alterations, these cases have findings that overlap with those corresponding to classic SMZL (symptomatology, morphology of bone marrow, lymph nodes, peripheral blood involvement, and immunophenotype). We suggest that these cases be considered a putative variant of SMZL.

Progression to large B-cell lymphoma in splenic marginal zone lymphoma: a description of a series of 12 cases

Splenic marginal zone lymphoma (SMZL) is considered to be an indolent extranodal B-cell lymphoma. Despite its low aggressivity, histologic progression has been described in sporadic reports, although the frequency, characteristics, and underlying molecular abnormalities of this phenomenon are largely unknown. We review here the clinical, morphologic, immunohistochemical, and molecular features of a series of 12 SMZL cases that showed progression to large B-cell lymphoma (LBCL). The most frequent location of secondary LBCL was in peripheral lymph node. This occurred between 12 and 85 months after diagnosis of SMZL. However, in two cases LBCL was diagnosed at the initial stage of the disease (one spleen tumoral nodule and one hilar lymph node). The histologic and immunophenotypic features of these cases were similar to those of transformed LBCL at other sites. In four cases the immunoglobulin heavy chain gene polymerase chain study revealed the same rearrangement pattern in both primary and secondary tumors, thereby confirming their identity and excluding the possibility of a second malignancy. As is the case with other low-grade lymphoproliferative disorders, SMZL may undergo high-grade transformation. These 12 cases represent 13% of our series of SMZL with adequate follow-up. The incidence of large cell transformation in SMZL seems to be lower than in follicular lymphoma (25-60%) and mantle cell lymphoma (11-39%), although it is similar to the frequency of transformation in B-chronic lymphocytic lymphoma/small lymphocytic lymphoma (1-10%). The mean proliferative index (MIB1 staining) in initial SMZL specimens of cases with LBCL transformation was 28.6%, higher than that of MIB1 staining in the overall SMZL series (21.8%), although not statistically significantly so. p53 or p16INK4a inactivation in this series was observed in only one case, in contrast with the situation observed in chronic lymphocytic leukemia, follicular lymphoma, and mantle cell lymphoma. It seems that progression in SMZL is mainly independent of p53 or p16INK4a inactivation. The frequency of the 7q deletion in this series was 3 of 7 (42%). 7q loss may play an alternative role in the inactivation of the p53 and p16INK4a pathway, thereby favoring tumoral progression.

Reference values for peripheral blood B-lymphocyte subpopulations: a basis for multiparametric immunophenotyping of abnormal lymphocytes

BACKGROUND AND OBJECTIVES

Immunophenotyping has become a useful tool for the differential diagnosis of chronic B-cell lymphoproliferative disorders. The aim of this work was to determine reference values of normal B-cell subpopulations.

MATERIAL AND METHODS

Blood samples from 38 healthy volunteers were analyzed by multidimensional flow cytometry, using a panel of directly conjugated antibodies. Results were expressed as percent of positive B cells and as median fluorescence intensity, an indirect assessment of the expression level.

RESULTS

CD20, CD22, CD24, CD40, CD79a, CD79b, FMC7, CD11a, CD18, CD44 were positive in the whole B cell population, whereas CD10, CD86, CD103, CD154 and FasL were almost absent from the B-lymphocyte population. 75% were IgD positive. The kappa/lambda ratio was 1.5. CD5, CD23, CD25, CD38, CD43, CD54, CD62L, CD80 and CD95 were positive in different B-cell subpopulations. The utility of all these markers in the differential diagnosis of chronic B-cell lymphoproliferative disorders is discussed.

CONCLUSION

In order to interpret a pathological immunophenotype, it is necessary to refer to quantitative and qualitative values of normal B-cell subpopulations.

Splenectomy influences bone marrow infiltration in patients with splenic marginal zone cell lymphoma with or without villous lymphocytes

BACKGROUND

Splenic marginal zone cell lymphoma (SMZL) is a low grade B-cell lymphoma in which patients can have circulating villous lymphocytes and can show a peculiar intrasinusoidal bone marrow (BM) infiltration. Splenectomy is the reported treatment of choice for these patients. The objective of this study was to evaluate the effects of splenectomy on patients with BM lymphomatous infiltration.

METHODS

BM biopsies of 16 patients with SMZL were studied morphologically and immunohistochemically. In 12 patients, BM biopsies were taken before and after splenectomy. Four patients did not undergo splenectomy, and their BM biopsies were performed with an approximately 1 year interval.

RESULTS

BM infiltration ranged from 10% to 40% of overall cellularity and was mostly of the intrasinusoidal type. After splenectomy, BM infiltration tended to become frankly nodular and showed an increase in tumor burden. Nonsplenectomized patients showed an unmodified picture.

CONCLUSIONS

Splenectomy seems to induce important changes in patients with BM infiltration, probably through the lack of microenvironmental factors on circulating cells. These effects suggest reconsidering the role of splenectomy in the treatment of patients with SMZL.

Splenic marginal zone lymphoma with or without plasmacytic differentiation

We report a series of 31 cases of splenic marginal zone lymphomas with an enlarged spleen and a multimicronodular macroscopic pattern. Two groups, A and B, were distinguished based on the presence (A) or absence (B) of a lymphoplasmacytic component with monoclonal immunoglobulin expression in the cytoplasm. There were no differences between the groups as far as age, sex, spleen weight, and progression. The only difference was the presence in group A of a monoclonal serum component and autoimmune disorders, particularly autoimmune hemolytic anemia. In most cases in which a liver and/or bone marrow biopsy was performed, lymphomatous infiltration was detected. Seven cases had a seric monoclonal IgM of 5 g/L or more and liver or bone marrow infiltration, corresponding to the definition of Waldenstrom's macroglobulinemia. Lymphoma cells had a monocytoid, centrocytoid and, in group A, lymphoplasmacytic morphology. The lymphomatous cells were positive for CD20, CD45 RA, and bcl-2. They expressed IgD in 9 cases, partially in 6, and were negative for IgD in 9 of the 24 cases studied. Progression seems to be slow, with a long survival. Three patients presented with transformation into a large B-cell lymphoma, which was responsible for death in two patients.

Anaplastic large cell lymphoma arising in bone: report of a case of the monomorphic variant with the t(2;5)(p23;q35) translocation

Anaplastic large cell lymphoma (ALCL) represents approximately 2% of all non-Hodgkin lymphomas according to the recent Non-Hodgkin Lymphoma Classification Project. As defined in the revised European-American classification of lymphoid neoplasms (REAL), ALCL is a neoplasm of T-cell or null-cell lineage; 20% to 60% of cases are associated with the t(2;5)(p23;q35) translocation. ALCL commonly involves nodal as well as a wide variety of extranodal sites, although primary or secondary involvement of bone is rare. We describe the case of a 71-year-old man with stage IE T-cell ALCL, monomorphic variant, arising in the left anterior fifth rib and involving adjacent soft tissue without other sites of disease. The monomorphic histologic features hindered the initial recognition of this neoplasm as ALCL. However, strong uniform CD30 antigen expression and subsequent demonstration of the t(2;5)(p23;q35) translocation and anaplastic lymphoma kinase (ALK) immunoreactivity led to the correct diagnosis. We identified only 5 reported cases of T-cell and null-cell ALCL arising in bone and only 2 of these cases involved a single bone site. All 5 previously reported cases were ALCL of the classic type. We report a case of ALCL that is unique to our knowledge. This case of monomorphic ALCL was localized to bone and tumor cells contained the t(2;5)(p23;q35) translocation.

Marginal zone B-cell lymphomas (MZBL) arising at different sites represent different biological entities

Most entities of B-cell malignant non-Hodgkin's lymphomas (NHL) are characterized by typical primary chromosomal changes such as the t(14;18) in follicular lymphoma or the t(11;14) in mantle cell lymphoma. In contrast, marginal zone B-cell lymphomas (MZBL), arising at different nodal and extranodal sites, are poorly characterized on the genetic level. We performed cytogenetic investigations in 20 splenic and in 10 nodal MZBL and analyzed 52 MZBL (including 12 MALT-type lymphomas) for deletions of TP53, D13S25, and RB1 loci by fluorescence in situ hybridization. A new nonrandom chromosomal aberration, del(10)(q22q24), was found as a clonal anomaly in 3 out of 20 cases of splenic MZBL. Further recurring abnormalities such as del(7q) or trisomy 3 were found to be characteristic chromosomal changes in a subset of splenic MZBL. TP53 was deleted in 5/25 cases of splenic MZBL. Deletions involving band 13q14 were only rarely encountered, challenging a previous report that stated a dissociated D13S25-RB1 status as characteristic in splenic MZBL. There are fundamental differences between the different subtypes of marginal zone lymphomas as defined with current classification schemes. Splenic MZBL, in contrast to most other entities of B-cell NHL, seems to constitute a heterogeneous disease especially with regard to genetic alterations. del(10)(q22q24) could be of importance at least in a subset of this lymphoma entity.

Analysis of the P53, RB/D13S25, and P16 tumor suppressor genes in marginal zone B-cell lymphoma: An interphase fluorescence in situ hybridization study

The genetic mechanisms underlying the genesis, disease progression, and high-grade transformation of marginal zone B-cell lymphoma (MZBCL) are poorly understood. We analyzed 33 cases of histologically and immunophenotypically well-characterized MZBCL (12 extranodal, 11 nodal, and 10 splenic MZBCL; 27 at primary diagnosis and six during the course of disease) by dual-color interphase fluorescence in situ hybridization (FISH) for deletions of tumor suppressor genes. We investigated loci known to play a role in the genesis or disease progression of other subtypes of lymphoid malignancies, namely the P53 gene (17p13), the retinoblastoma gene (RB, 13q14), the D13S25 locus (13q14), and the P16(INK4A) gene (9p21). Heterozygous deletions of P53 were detected in three out of the 33 cases, including two splenic and one extranodal MZBCL. One of these patients was analyzed at primary diagnosis and two during the course of disease. Heterozygous deletions of the RB gene (nodal MZBCL) and D13S25 (splenic MZBCL) were found in one case each. P16 deletions were not detected in any of our cases. We conclude that deletions of the analyzed tumor suppressor genes are relatively rare in MZBCL, which contrasts with the findings in some other subtypes of NHL.

Splenic marginal zone lymphoma with increased number of blasts: an aggressive variant?

Splenic marginal zone lymphoma (SMZL) is a recently described and distinctive type of splenic lymphoma and is characterized by an indolent clinical course. By analyzing a large series of SMZL cases, we recognized the existence of a subset of 6 cases characterized by an aggressive clinical course that led to death caused by the tumor in 5 of 6 cases, whereas the remaining patient showed signs of tumor progression. The morphological, immunohistological, and molecular study of these cases has allowed us to detect precise distinctive features of this SMZL variant. The cases included here were characterized by massive splenomegaly and a morphological picture showing a micronodular pattern of splenic involvement with follicle replacement, biphasic cytology, and marginal zone differentiation. Unlike classical SMZL cases, a conspicuous component of larger lymphocytes was distributed in the marginal zone ring, occasionally overrunning it, with isolated presence of the same cells within the central small cell component and also in the red pulp. The bone marrow and peripheral lymph nodes showed similar histological findings to those described for SMZL in these locations. The genetic and molecular study of these cases showed no alterations specific to other lymphoma types, such as t14;18 and t11;14. Instead of this, it showed 7q loss in 3 of 5 cases, p53 inactivation in 2 of 6 cases, cyclinD1 overexpression in 2 of 6 cases, and the presence of translocations involving the 1q32 region in 2 of 4 cases. The recognition of this aggressive variant, besides offering a prognostic indication, could lead to a more suitable form of clinical management of these patients. Further molecular studies would clarify the role of the different genetic alterations found.

Splenic marginal zone lymphomas of mice

Splenic marginal zone lymphomas (MZLs) have been found to occur at a high frequency in NFS.N mice congenic for high-expressing ecotropic murine leukemia virus (MuLV) genes from AKR and C58 mice. Based on morphological, immunological, and molecular studies of these mice, MZL is clearly recognizable as a distinct disease with a characteristic clinical behavior. MZL was staged according to the degree of accumulation and morphological change of cells within the splenic marginal zone, as follows: 1) a moderate increase in normal-looking MZ cells, judged to be prelymphomatous, and 2) MZL in three variants: i) distinct enlargement of MZ by normal-looking cells (MZL), ii) distinct enlargement of MZ by basophilic centroblast-like cells (MZL+), and iii) extensive splenic involvement by centroblast-like cells (MZL++). The rate of mitosis and apoptosis increases with lymphoma grade. In most cases, emergence of a dominant IgH clonal pattern in paired splenic biopsy and necropsy samples was correlated with progression. MZLs were transplantable and homed to the spleen. MZL may constitute a commonly occurring lymphoma type unrecognized, in part, because of the centroblastic morphology of high-grade MZL and possible overgrowth of lower-grade MZL by more aggressive follicular lymphomas.

Primary nodal marginal zone lymphomas of splenic and MALT type

The existence of primary nodal marginal zone lymphomas (MZL) is controversial, as is their relationship to putative extranodal counterparts. Most nodal lymphomas with monocytoid B cell/marginal zone differentiation exhibit the morphologic and immunophenotypical characteristics of extranodal MALT-lymphomas. Splenic marginal zone lymphoma (SMZL) is also of putative marginal zone derivation, but it differs immunophenotypically from MALT lymphoma. To clarify the relationship between nodal and extranodal MZLs and to investigate the possible existence of a nodal variant of SMZL, 36 MZL initially considered to be primary nodal neoplasms were examined. Other low-grade lymphomas with marginal zone differentiation were excluded (small lymphocytic lymphoma/chronic lymphocytic leukemia [SLL/CLL], follicular lymphoma, and mantle cell lymphoma). Six nodal MZLs showed morphologic and phenotypic characteristics similar to those of SMZL, whereas 30 tumors were more similar to MALT-type lymphomas. The six tumors with SMZL features showed a polymorphic infiltrate surrounding residual germinal centers with absent or very attenuated mantle cuffs. These lymphomas were IgD positive (6/6) but cyclin D1 (0/5), CD5 (0/6), and CD23 (0/6) negative. Five of these patients came for treatment in stage I or II. No patient manifested splenomegaly, peripheral blood, and/or bone marrow infiltration either at diagnosis or during follow-up. Lymph nodes from 30 patients with MALT-type features showed a perisinusoidal and perivascular infiltration of monocytoid/centrocytoid cells and residual germinal centers with a relatively well-preserved mantle cuff. The neoplastic cells were negative for IgD (0/17), cyclin D1 (0/8), and CD5 (0/12). Seven of 16 (44%) patients with a detailed history and clinical follow-up had evidence of extranodal lymphoma. These observations suggest that most nodal B cell lymphomas with marginal zone differentiation are of the MALT type and that they are frequently associated with an extranodal component. In addition, a primary nodal counterpart of splenic MZL also exists, and may occur in the absence of splenomegaly.

Mutation Analysis of the Rearranged Immunoglobulin Heavy Chain Genes of Marginal Zone Cell Lymphomas Indicates an Origin From Different Marginal Zone B Lymphocyte Subsets

Marginal zone cell lymphoma is a recently described entity among the non-Hodgkin's lymphomas. It likely originates from the marginal zone B cells in the spleen and equivalent cells in the lymph node and extranodal tissues. Recent evidence indicates that marginal zone B cells are functionally heterogeneous and may differ with respect to the pattern of somatic hypermutation in their Ig variable genes. To test whether marginal zone lymphomas may originate from different subsets of marginal zone B cells, we performed a sequence and mutation analysis of the rearranged Ig heavy chain (IgH) variable genes (Vh) of a series of 14 cases of marginal zone lymphoma, occurring in the spleen (4), the lymph node (4), the stomach (2), the orbit (2), the tongue (1), and the skin (1). Our data show that marginal zone cell lymphomas preferentially rearrange the Vh4, Vh3, and Vh1 family genes, without preference for any particular Vh gene. Somatic mutations are present in 13 cases; one case of marginal zone cell lymphoma of the skin showed a germline configuration of the rearranged Vh gene. Mutation analysis shows evidence of antigen selection in three cases of marginal zone cell lymphoma, one of the spleen, stomach, and orbit, respectively. No evidence of antigen selection was present in the other cases. These data indicate that marginal zone cell lymphomas may arise from different subsets of marginal zone B cells. In addition, lymphomagenesis may not be triggered by antigen in all cases of marginal zone cell lymphoma.

Mutation Analysis of the Rearranged Immunoglobulin Heavy Chain Genes of Marginal Zone Cell Lymphomas Indicates an Origin From Different Marginal Zone B Lymphocyte Subsets

Marginal zone cell lymphoma is a recently described entity among the non-Hodgkin's lymphomas. It likely originates from the marginal zone B cells in the spleen and equivalent cells in the lymph node and extranodal tissues. Recent evidence indicates that marginal zone B cells are functionally heterogeneous and may differ with respect to the pattern of somatic hypermutation in their Ig variable genes. To test whether marginal zone lymphomas may originate from different subsets of marginal zone B cells, we performed a sequence and mutation analysis of the rearranged Ig heavy chain (IgH) variable genes (Vh) of a series of 14 cases of marginal zone lymphoma, occurring in the spleen (4), the lymph node (4), the stomach (2), the orbit (2), the tongue (1), and the skin (1). Our data show that marginal zone cell lymphomas preferentially rearrange the Vh4, Vh3, and Vh1 family genes, without preference for any particular Vh gene. Somatic mutations are present in 13 cases; one case of marginal zone cell lymphoma of the skin showed a germline configuration of the rearranged Vh gene. Mutation analysis shows evidence of antigen selection in three cases of marginal zone cell lymphoma, one of the spleen, stomach, and orbit, respectively. No evidence of antigen selection was present in the other cases. These data indicate that marginal zone cell lymphomas may arise from different subsets of marginal zone B cells. In addition, lymphomagenesis may not be triggered by antigen in all cases of marginal zone cell lymphoma.

Immunological abnormalities in splenic marginal zone cell lymphoma

The clinical features of patients with splenic marginal zone cell lymphoma (SMZCL) have rarely been reported. In the present study, immunological abnormalities, particularly hematological abnormalities, observed in SMZCL were described. Autoimmune hemolytic anemia, immune thrombocytopenia, and appearance of lupus anticoagulant were observed in 2 of 3 patients with SMZCL. Other abnormal data including monoclonal gammopathy and cold agglutinin were also observed in 2 of the 3 patients. Immunological abnormalities may be characteristic complications in patients with SMZCL and must be followed carefully, since they may be a reliable marker of this type of lymphoma activity.

Marginal zone B-cell lymphomas including mucosa-associated lymphoid tissue type lymphoma (MALT), monocytoid B-cell lymphoma and splenic marginal zone cell lymphoma and their relation to the reactive marginal zone

The marginal zone of the B follicle represents a well-defined compartment of the B area. Its cellular composition is distinct from that of the follicle centre, from which it also differs in its functional role in the immune response. Several newly identified lymphoma entities, e.g. extranodal MALT type lymphoma, nodal monocytoid B-cell lymphoma and splenic marginal zone B-cell lymphoma, display in common a very peculiar organoid growth pattern reminiscent of the marginal zone. Moreover, their neoplastic components share morphologic and phenotypic similarities to the cellular components of the marginal zone. The clinical characteristics of these various marginal zone cell lymphomas may differ depending of the organ which is involved. Nevertheless, they all share common cytogenetic abnormalities suggesting a common pathogenesis.