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

The many faces of nodal and splenic marginal zone lymphomas. A report of the 2022 EA4HP/SH lymphoma workshop

Session 3 of the lymphoma workshop of the XXI joint meeting of the European Association for Haematopathology and the Society for Hematopathology took place in Florence, Italy, on September 22, 2022. The topics of this session were splenic and nodal marginal zone lymphomas, transformation in marginal zone lymphomas, and pediatric nodal marginal zone lymphomas and their differential diagnosis as well as related entities. Forty-two cases in these categories were submitted to the workshop, including splenic lymphomas (marginal zone and diffuse red pulp lymphomas), transformed marginal zone lymphomas (splenic and nodal), nodal marginal zone lymphomas with increased TFH-cells, and pediatric nodal marginal zone lymphomas. The case review highlighted some of the principal problems in the diagnosis of marginal zone lymphomas, including the difficulties in the distinction between splenic marginal zone lymphoma, splenic diffuse red pulp lymphoma, and hairy cell leukemia variant/splenic B-cell lymphoma with prominent nucleoli which requires integration of clinical features, immunophenotype, and morphology in blood, bone marrow, and spleen; cases of marginal zone lymphoma with markedly increased TFH-cells, simulating a T-cell lymphoma, where molecular studies (clonality and mutation detection) can help to establish the final diagnosis; the criteria for transformation of marginal zone lymphomas, which are still unclear and might require the integration of morphological and molecular data; the concept of an overlapping spectrum between pediatric nodal marginal zone lymphoma and pediatric-type follicular lymphoma; and the distinction between pediatric nodal marginal zone lymphoma and "atypical" marginal zone hyperplasia, where molecular studies are mandatory to correctly classify cases.

Splenic Lymphomas: A Tertiary Care Center Experience and Review of Literature

Primary splenic lymphomas are rare with the majority of lymphomas in spleen being secondary to an extra-splenic lymphoma. We aimed to analyze the epidemiological profile of the splenic lymphoma and review the literature. This was a retrospective study including all splenectomies and splenic biopsies from 2015 to September 2021. All the cases were retrieved from Department of Pathology. Detailed histopathological, clinical and demographic evaluation was done. All the lymphomas were classified according to WHO 2016 classification. A total of 714 splenectomies were performed for a variety of benign causes, as part of tumor resections and for the diagnosis of lymphoma. Few core biopsies were also included. A total of 33 lymphomas diagnosed in the spleen, primary splenic lymphomas constituted 84.84% (n = 28) of the cohort with 5 (15.15%) having the primary site elsewhere. The primary splenic lymphomas constituted 0.28% of all the lymphomas arising at various sites. Adult population (19-65 years) formed the bulk (78.78%) with a slight male preponderance. Splenic marginal zone lymphomas (n = 15, 45.45%) comprised of major proportion of cases followed by primary splenic diffuse large B-cell lymphoma (n = 4, 12.12%). Splenectomy was the main course of treatment for SMZL with a good overall outcome, with chemotherapy ± radiotherapy forming the mainstay in other lymphomas. Lymphomas in spleen can be infiltrative or a primary, hence proper clinic-radiological and pathological evaluation is required. Appropriate management is guided by the precise and detailed evaluation by the pathologist, requiring understanding of the same.

Immunoglobulin D (IgD) and IgD receptor expression in diffuse large B-cell lymphoma

Objective: Immunoglobulin D (IgD) levels are often elevated in patients with autoimmune diseases. However, the oncogenic activities of IgD and IgD receptor (IgDR) in diffuse large B-cell lymphoma (DLBCL) have not been reported in detail. Therefore, we aimed to investigate the expression of IgD and IgDR in patients with DLBCL. Methods: Membrane IgD (mIgD) and IgDR expression in tissue samples was analyzed using IHC, mIgD and IgDR expression on peripheral blood mononuclear cells (PBMCs) was analyzed by FCM, and secreted IgD (sIgD) level was analyzed by ELISA. Fisher's exact test and Spearman correlation analysis were used to evaluate the relationship between IgD, IgDR, and clinical parameters. Results: The pathological lymph nodes of 34 patients with DLBCL were studied, and mIgD and IgDR expression was found in 16 and 19 patients. mIgD and IgDR expression was upregulated in patients with DLBCL and mIgD expression was significantly associated with IgDR expression. Further correlation analysis showed that mIgD expression was correlated with serum β₂-MG level and Hans algorithm as germinal center B (GCB), whereas IgDR expression correlated with serum LDH level, IPI score and GCB. ELISA showed that sIgD level was significantly increased in DLBCL patients and it correlated with serum β₂-MG and LDH levels. FCM showed that mIgD and IgDR expression in PBMCs of patients with DLBCL was significantly higher than that in healthy controls. Conclusion: Our findings suggest that overexpression of IgD and IgDR is an abnormal activation state in DLBCL.

Use of Smooth Muscle Myosin Heavy Chain as an Effective Marker of Follicular Dendritic Cells

Smooth muscle myosin heavy chain (SMMHC) is a major structural component of the contractile apparatus in smooth muscle cells. Even though it is considered a relatively specific marker for terminal smooth muscle cell differentiation, expression in other cell types such as follicular dendritic cells (FDCs) has rarely been reported. To determine whether SMMHC represents an effective FDC marker in lymphoid tissues, we compared the immunohistochemical results for SMMHC with those of the traditional FDC markers podoplanin (D2-40) and CD21. Paraffin sections of 44 lymphoid tissues were analyzed, including 31 cases of follicular hyperplasia, 6 cases of follicular lymphoma, 2 cases of peripheral T-cell lymphoma, 3 cases of diffuse large B-cell lymphoma arising in follicular lymphoma, 1 case of nodular sclerosis classical Hodgkin lymphoma, and 1 case of small lymphocytic lymphoma. There was no statistically significant difference between the number of SMMHC-positive and D2-40-positive or CD21 lymph nodes (P>0.05). The extent and intensity of SMMHC-positive FDCs were similar to those of D2-40-positive FDCs (P=0.127 and 0.733, respectively), but significantly lower compared with those of CD21 cells (P=0.009 and 0.00002, respectively). However, in contrast to CD21 which was also positive in some germinal center B cells, SMMHC expression was restricted to FDCs. Our results indicate that SMMHC is an excellent marker for FDCs and can be particularly helpful in demonstrating the underlying architecture in lymphoid processes.

Splenic marginal zone lymphoma

Splenic marginal zone lymphoma (SMZL) is an indolent small B-cell lymphoma involving the spleen and bone marrow characterized by a micronodular tumoral infiltration that replaces the preexisting lymphoid follicles and shows marginal zone differentiation as a distinctive finding. SMZL cases are characterized by prominent splenomegaly and bone marrow and peripheral blood infiltration. Cells in peripheral blood show a villous cytology. Bone marrow and peripheral blood characteristic features usually allow a diagnosis of SMZL to be performed. Mutational spectrum of SMZL identifies specific findings, such as 7q loss and NOTCH2 and KLF2 mutations, both genes related with marginal zone differentiation. There is a striking clinical variability in SMZL cases, dependent of the tumoral load and performance status. Specific molecular markers such as 7q loss, p53 loss/mutation, NOTCH2 and KLF2 mutations have been found to be associated with the clinical variability. Distinction from Monoclonal B-cell lymphocytosis with marginal zone phenotype is still an open issue that requires identification of precise and specific thresholds with clinical meaning.

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.

Splenic marginal zone B-cell lymphoma: a distinct clinicopathological and molecular entity. Recent advances in ontogeny and classification

PURPOSE OF REVIEW

Indolent B-cell lymphomas that are supposed to derive from marginal zone encompass three distinct entities: extranodal marginal zone lymphoma (MZL) or mucosa-associated lymphatic tissue (MALT), nodal MZL (NMZL) and splenic MZL (SMZL). Although MALT lymphoma is well characterized and extensively studied at the clinical and molecular levels, SMZL and NMZL remain incompletely characterized. However, during the last years, the clinical and molecular heterogeneity of SMZL has been clarified. The recent 2008 WHO classification has maintained the distinction between the three diseases according to the organ where it arises and introduced a new provisional category of unclassified splenic lymphoma for overlapping entities, splenic diffuse red pulp lymphoma (SDRPL) and hairy cell leukemia-variant (HCL-V).

RECENT FINDINGS

Recent findings in SMZL contributed to a better characterization, including the few cases associated with hepatitis C, the recurrence of 7q deletion and the possibility of CD5 expression. Furthermore, the peculiar pattern of immunoglobulin heavy chain genes mutations and the biased usage of immunoglobulin heavy chain variable region genes (IGHV)1-2 segment are suggestive of a T-independent antigen driven proliferation, at least at initial steps. This review will focus on recent findings and differential diagnosis with SDRPL and HCL-V.

SUMMARY

The conjunction of morphologic, cytogenetic and clinical data has increased diagnosis reproducibility.

Marginal zone lymphomas with monocytoid morphology express T-bet and are associated with a low number of T cells in extranodal locations

The presence of tumor cells with monocytoid morphology in marginal zone lymphoma (MZL) has been described previously. Reactive monocytoid B cells bear a distinct immunophenotype and typically express T-bet, which clearly distinguishes them from nodal marginal zone B cells. The latter are positive for CD27 and negative for T-bet. We analyzed 74 MZLs for the expression of T-bet and correlated these results with the presence of monocytoid morphology. Expression of T-bet correlated with the presence of monocytoid morphology in MZLs. In analogy to reactive monocytoid B lymphocytes, we also found a significantly lower relative amount of intratumoral T lymphocytes in extranodal MZL with monocytoid morphology.

Mantle cell lymphoma cell lines show no evident immunoglobulin heavy chain stereotypy but frequent light chain stereotypy

Mantle cell lymphoma shows a peculiar immunogenetic profile, but the functional consequences of this fact are unknown. We have determined the precise sequences of rearranged heavy and light chain genes in several mantle cell lymphoma cell lines and investigated the presence of heavy and light chain stereotypy. These cell lines use IGHV and IGLV genes that are known to be preferentially rearranged in mantle cell lymphoma, but we found no evidence of heavy chain stereotypy. In contrast, one cell line (Mino) showed a nearly identical light chain complementarity-determining region 3 when compared to the only published light chain cluster. Two cell line couples (Jeko-1/UPN-2 and JVM-2/JVM-13) showed a highly similar light chain that satisfied the criteria for stereotypy. Our data show that mantle cell lymphoma cell lines resemble the IGHV and IGLV usage of mantle cell lymphoma, and foster the hypothesis that light chain stereotypy might be under-recognized.

B cell receptor and antigens in CLL

Nowadays, chronic lymphocytic leukemia (CLL) is considered as a prototypic antigen-driven lymphoma, with antigenic stimuli from the microenvironment promoting tumor outgrowth. Antigen recognition is a function of both the clonotypic B cell receptor immunoglobulin (BcR IG) and various other immune sensors, e.g., the Toll-like receptors. The critical role of BcR IG-mediated signaling in CLL development and evolution is underscored by the following: the disease-biased IG gene repertoire; the subdivision of CLL based on the somatic hypermutation load of the BcR IG into two broad categories with vastly different prognosis and eventual outcome; the existence of subsets of cases with distinct, quasi-identical (stereotyped) BcR IGs; and the clinical efficacy of novel therapeutics inhibiting BcR signaling. Here, we trace the immunogenetic evidence for antigen selection in CLL and also consider the types of implicated antigens as well as the immune signaling pathways relevant for CLL ontogeny and clonal progression.

Extranodal and splenic small B-cell lymphoma

Although almost any non-Hodgkin lymphoma can involve the spleen or an extranodal site as part of more widely disseminated disease, there is a group of small B-cell lymphomas that specifically arise in these locations. These are important to recognise as some appear to have a behaviour and prognosis that is distinct from their nodal counterparts. In addition, there are entities that are specific to extranodal locations (such as extranodal marginal zone lymphoma) and to the red or white pulp of the spleen. In this review, the characteristics of these entities will be presented as well as clues to help distinguish lymphoma from reactive infiltrates in extranodal sites and measure to distinguish between small B-cell lymphomas encountered in the spleen and at extranodal locations.

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 B-Cell Lymphomas/Leukemias

The diagnosis and classification of lymphoproliferative disorders in the spleen are frequently challenging. While some lymphomas, such as hairy cell leukemia and splenic marginal zone lymphoma, characteristically present with primarily splenic involvement, secondary involvement of the spleen may be seen with any lymphoma. Precise classification requires integration of the morphologic findings with clinical data, phenotypic studies, and often cytogenetic and/or molecular genetic analysis. Correlation with the findings in peripheral blood and bone marrow may also be required in some cases. This article discusses the diagnostic approach to splenic-based lymphoproliferative disorders in routine practice and describes the clinicopathologic features of lymphoid neoplasms that characteristically present in the spleen.

Defining the borders of splenic marginal zone lymphoma: a multiparameter study

Classic splenic marginal zone lymphomas are CD5-, CD10-, CD23-, CD43-, and usually IgD+ with biphasic white pulp nodules. However, the 2008 World Health Organization classification accepts splenic marginal zone lymphomas with monophasic marginal zone-like white pulp nodules and recognizes a group of unclassifiable splenic small B-cell lymphomas. To explore the relationship of classic splenic marginal zone lymphomas to these other less well-defined splenic lymphomas, a multiparameter study of 47 splenic marginal zone lymphomas and unclassifiable splenic small B-cell lymphomas was performed. Seventeen of 31 splenic marginal zone lymphomas were biphasic, and 14 were monophasic (90%-100% marginal zone-like white pulp nodules). Sixteen cases were unclassifiable splenic small B-cell lymphomas, most lacking a marginal zone-type component. There were many clinical similarities between the 3 groups, including similar survivals. Monophasic and unclassifiable cases were less likely to have a typical splenic marginal zone lymphoma phenotype (28.6%, 23.1%) compared with biphasic cases (86.7%), usually because of IgD negativity (P < .003). Thirty-four of 42 (81%) cases had cytogenetic abnormalities by fluorescence in situ hybridization; and 17 of 20 (85%), by classical cytogenetics. The most frequent fluorescence in situ hybridization abnormalities among the splenic marginal zone lymphomas were del(7)(q31) (26%), +12 (25%), and +3q27 (27%); and among the unclassifiable cases, +12 (50%) and +3q27 (36%). Five of 6 unclassifiable cases with exclusively small non-marginal zone-like lymphocytes involving both white and red pulp had +12 compared with 9 of 34 other cases (P < .02). CDK6 (2 cases) and BCL3 (1 case) rearrangements were only seen in the unclassifiable group. These results support including both biphasic and monophasic cases as splenic marginal zone lymphomas, but suggest that the lack of a non-marginal zone-like population in the monophasic group is associated with some biologic differences. They also demonstrate a relatively large proportion of unclassifiable cases, including a group with frequent +12.

Splenic diffuse red pulp small B-cell lymphoma: revision of a series of cases reveals characteristic clinico-pathological features

BACKGROUND

Splenic diffuse red pulp small B-cell lymphoma is an uncommon B-cell lymphoma, now recognized as a provisional entity in the 2008 update of the WHO Classification. Additional work is required to review this entity and establish its diagnostic features.

DESIGN AND METHODS

We have retrospectively analyzed the disease features in a highly selected series of 17 patients diagnosed as splenic diffuse red pulp small B-cell lymphoma.

RESULTS

The median age was 65.5 years (range 40-79 years) and there was a predominance of males (male/female ratio: 2.4). Clinical manifestations were mainly derived from splenomegaly. Splenectomy was the front-line treatment in 11 symptomatic patients; the remaining 6 received chemotherapy initially followed by splenectomy. After a mean follow-up of 72 months, the five-year overall survival was 93%. All cases showed a purely diffuse pattern of splenic infiltration by monomorphous small cells with small round nuclei and pale cytoplasm. All bone marrow biopsies showed tumoral infiltration, with intrasinusoidal infiltration. Peripheral blood cells were small to medium-sized, with clumped chromatin and round nuclear outline and villous cytoplasm. Neoplastic cells had a CD20(+), CD23(-), bcl6(-), Annexin A1- phenotype, with frequent expression of DBA44+ (15/17) and IgG (10/15). FCM data had a B-cell phenotype (CD19(+), CD20(+), CD22(+)) with FMC7 (10/11) and CD11c (5/8) expression. Clonal IgH rearrangement studies in 4 cases showed IgVH mutations in all cases, without VH1.2 usage.

CONCLUSIONS

Our data suggest that splenic diffuse red pulp small B-cell lymphoma is a distinct entity with morphological and immunophenotypical features that differ from those of other splenic 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.

Primary cystic lung light chain deposition disease: a clinicopathologic entity derived from unmutated B cells with a stereotyped IGHV4-34/IGKV1 receptor

We have recently described a new form of light chain deposition disease (LCDD) presenting as a severe cystic lung disorder requiring lung transplantation. There was no bone marrow plasma cell proliferation. Because of the absence of disease recurrence after bilateral lung transplantation and of serum-free light chain ratio normalization after the procedure, we hypothesized that monoclonal light chain synthesis occurred within the lung. The aim of this study was to look for the monoclonal B-cell component in 3 patients with cystic lung LCDD. Histologic examination of the explanted lungs showed diffuse nonamyloid kappa light chain deposits associated with a mild lymphoid infiltrate composed of aggregates of small CD20(+), CD5(-), CD10(-) B lymphocytes reminiscent of bronchus-associated lymphoid tissue. Using polymerase chain reaction (PCR), we identified a dominant B-cell clone in the lung in the 3 studied patients. The clonal expansion of each patient shared an unmutated antigen receptor variable region sequence characterized by the use of IGHV4-34 and IGKV1 subgroups with heavy and light chain CDR3 sequences of more than 80% amino acid identity, a feature evocative of an antigen-driven process. Combined with clinical and biologic data, our results strongly argue for a new antigen-driven primary pulmonary lymphoproliferative disorder.

Application of Immunohistochemistry in the Diagnosis of Non-Hodgkin and Hodgkin Lymphoma

Context.—Beginning with the immunologic classifications of Lukes and Collins and Kiel and culminating in the Revised European-American Lymphoma and World Health Organization classifications, the diagnosis of lymphoid tumors relies heavily on the determination of cell lineage, maturation, and function, based on antigen expression in addition to morphology and clinical features. Technologic advances in immunology, antibody production, genetic analysis, cloning, and the identification of new genes and proteins by microarray and proteomics have provided pathologists with many antibodies to use in routine diagnosis.

Objective.—To provide guidance to the practicing pathologist in the appropriate selection of an antibody panel for the diagnosis of lymphoma based on morphology and relevant clinical data and to avoid pitfalls in the interpretation of immunohistochemical data. Attention is given to some of the newer antibodies, particularly against transcription factors, that are diagnostically and prognostically useful.

Data Sources.—The information presented in this article is based on review of the literature using the OVID database (Ovid MEDLINE 1950 to present with daily update) and 20 years of experience in diagnostic hematopathology.

Conclusions.—Immunophenotyping is required for the diagnosis and classification of lymphoid malignancies. Many paraffin-reactive antibodies are available to the pathologist but most are not specific. To avoid diagnostic pitfalls, interpretation of marker studies must be based on a panel and knowledge of a particular antigen's expression in normal, reactive, and neoplastic conditions.

Splenic red pulp lymphoma with numerous basophilic villous lymphocytes: a distinct clinicopathologic and molecular entity?

The presence of circulating villous lymphocytes (VLs) in lymphoma patients usually points to splenic marginal zone B-cell lymphoma (SMZL), even if the VLs can be found occasionally in other small B-cell lymphomas. However, those cells are variably described, and detailed cytologic characterization is often lacking. We identified lymphoma cases with numerous basophilic VLs among the large group of splenic lymphoma with VLs, and for further delineation, 37 cases with this particular cytology were analyzed. Patients, predominantly older men, presented with moderate lymphocytosis and splenomegaly without pancytopenia. The monoclonal B cells expressed IgM + D, IgM + G, IgM or IgG, as well as CD76 and CD11c, frequently CD103, and rarely CD123. Spleen sections were peculiar, with atrophic white pulp and a monomorphic diffuse lymphoma infiltration in a congested red pulp. Bone marrow infiltration was interstitial and intrasinusoidal without extensive fibrosis. Cytogenetic analysis showed a frequent absence of clonal aberrations (68%). Most cases (79%) were IgH mutated, with an overrepresentation of VH3 and VH4 gene families. These results, as well as the clinical evolution, show that those lymphoma cases represent a homogeneous group distinct from SMZL and reminiscent of hairy cell leukemia variant, perhaps corresponding to a separate lymphoma entity.

Splenic marginal zone lymphoma proposals for a revision of diagnostic, staging and therapeutic criteria

Since the initial description of splenic marginal zone lymphoma (SMZL) in 1992, an increasing number of publications have dealt with multiple aspects of SMZL diagnosis, molecular pathogenesis and treatment. This process has identified multiple inconsistencies in the diagnostic criteria and lack of clear guidelines for the staging and treatment. The authors of this review have held several meetings and exchanged series of cases with the objective of agreeing on the main diagnostic, staging and therapeutic guidelines for patients with this condition. Specific working groups were created for diagnostic criteria, immunophenotype, staging and treatment. As results of this work, guidelines are proposed for diagnosis, differential diagnosis, staging, prognostic factors, treatment and response criteria. The guidelines proposed here are intended to contribute to the standardization of the diagnosis and treatment of these patients, and should facilitate the future development of clinical trials that could define more precisely predictive markers for histological progression or lack of response, and evaluate new drugs or treatments.

Podoplanin (D2-40) is a novel marker for follicular dendritic cell tumors

Podoplanin, recognized by monoclonal antibody D2-40, may be a useful marker for follicular dendritic cell (FDC) tumors. Paraffin sections of 125 dendritic cell, histiocytic, and spindle cell lesions were studied, including 11 FDC tumors, 5 interdigitating dendritic cell tumors, 10 histiocytic sarcomas, 5 Langerhans cell histiocytosis, 5 sinus histiocytosis with massive lymphadenopathy, 5 inflammatory pseudotumors of lymph node or spleen, 9 nodal Kaposi sarcomas, 6 inflammatory myofibroblastic tumors (IMTs), 29 gastrointestinal stromal tumors (GISTs), and 10 cases each of malignant peripheral nerve sheath tumor, leiomyosarcoma, monophasic synovial sarcoma (SS), and solitary fibrous tumor. All FDC tumors and Kaposi sarcomas showed strong immunoreactivity for podoplanin (predominantly membranous). Podoplanin expression was only occasionally observed in the other tumor types, including 7 GISTs (24%), 2 IMTs (33%), and 3 SS (30%), and was generally weak and cytoplasmic. Reactivity for podoplanin was more common in spindle cell GISTs (5/13 [38%]) than in epithelioid or mixed-type GISTs (2/16 [13%]). Podoplanin is a highly sensitive marker for FDC tumors and may be useful to help confirm the diagnosis in conjunction with conventional FDC markers, particularly in the differential diagnosis of dendritic cell and histiocytic lesions.