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

Untangling hairy cell leukaemia (HCL) variant and other HCL-like disorders: Diagnosis and treatment

The variant form of hairy cell leukaemia (HCL-V) is a rare disease very different from hairy cell leukaemia (HCL), which is a very well-defined entity. The 5th WHO edition (Leukemia, 36, 2022 and 1720) classification (WHO-HAEM5) introduced splenic lymphomas/leukaemias including four different entities: (1) HCL, (2) splenic marginal zone lymphoma (SMZL) with circulating villous cells in the peripheral blood, (3) splenic lymphoma with prominent nucleolus (SLPN), which replaced HCL-V and CD5 negative B-prolymphocytic leukaemia (B-PLL), and (4) splenic diffuse red pulp lymphoma (SDRPL). All these entities have to be distinguished because of a different clinical course and the need for a different treatment. The diagnosis can be challenging because of complex cases and overlap and/or grey zones between all the entities and needs integrating clinical, histologic, immunophenotypic, cytogenetic and molecular data. We review the diagnostic criteria including clinical, immunophenotypic and molecular characteristics of patients with HCL-V and other HCL-like disorders including HCL, SDRPL, SMZL, B-PLL and the Japanese form of HCL. We also discuss the different criteria allowing us to separate these different entities and we will update the recent therapeutic options that have emerged, in particular the advances with chemoimmunotherapy and/or targeted therapies.

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.

Epidermotropic B-Cell Lymphoma: A Case of Secondary Cutaneous Splenic Marginal Zone B-Cell Lymphoma With Autoinvolutive and Recurrent Cutaneous Lesions

ABSTRACT

An 84-year-old woman presented with a 3-month history of a papular rash on the trunk, abdomen, and back. Histopathological examination revealed atypical lymphoid deep and band-like dermal infiltrates with marked epidermotropism. Neoplastic cells expressed B-cell markers (CD20), and clonal immunoglobulin gene rearrangement was observed. A complete peripheral blood study revealed aberrant circulating villous lymphocytes with the expression of B-cell markers (CD20, CD22, and CD79a) and aberrant expression of CD5. A staging workup revealed discrete splenic enlargement and bone marrow and gastrointestinal tract involvement. Skin lesions regressed spontaneously several weeks after diagnosis. Throughout evolution, the patient developed scattered cutaneous nodules and generalized papulo-nodules showing either epidermotropic or nonepidermotropic atypical dermal lymphoid infiltrates. This case illustrates the observation of autoinvolutive and recurrent epidermotropic B-cell atypical cutaneous infiltrates as a characteristic feature of secondary cutaneous involvement in splenic marginal B-cell lymphoma. Previously reported cases of epidermotropic B-cell lymphoma have been reviewed. Concurrent and simultaneous observation of epidermotropic and nonepidermotropic lesions seems to indicate that epidermotropism is an important but nonconstant diagnostic feature of splenic marginal B-cell lymphoma.

Hairy Cell Leukemia-Japanese Variant: Report of a Patient and Literature Review

Hairy cell leukemia-Japanese variant (HCL-jv) shares some features with, but differs in other features from, HCL variant. Recently, it has been pointed out that HCL-jv and splenic diffuse red pulp small B-cell lymphoma (SDRPL) possibly constitute the same disease. We report a patient with HCL-jv, in which the neoplastic cells in the resected spleen were positive for CD11c, CD103, tartrate-resistant acid phosphatase (by immunohistochemistry), and weakly positive for cyclin D3. They were negative for CD25, CD123, annexin A1, and BRAF V600E-derived protein. Meta-analysis of HCL-jv cases in the literature showed considerable variation in the expression of HCL-related molecules. Although the clinical features and pattern of splenic involvement of HCL-jv are similar to those of SDRPL, some cytomorphological and phenotypical differences can be pointed out. To confirm whether the weak expression of cyclin D3 in our case suggests a spectrum from HCL-jv to SDRPL or one of the characteristics of HCL-jv, further studies on a large number of cases are necessary.

B-cell neoplasms and Hodgkin lymphoma in the spleen

B-cell lymphoma of spleen may be primary (most commonly splenic diffuse large B-cell lymphoma) or secondary (typically low-grade non-Hodgkin lymphoma). Depending on the specific lymphoma subtype, there may be a predominantly white pulp pattern of involvement, a predominantly red pulp pattern or a focal nodular pattern. Splenectomy is the ideal specimen for a multiparametric integrative diagnosis of splenic lymphoma, as it allows for a combined study of morphology, immunohistology, flow cytometry, cytogenetics, and molecular genetic techniques. This review article describes the clinicopathologic characteristics of all the relevant B-cell neoplasms that may be encountered in a splenic biopsy or a splenectomy specimen.

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 diffuse red-pulp small B-cell lymphoma associated with hepatitis B virus: a report of two cases

CONTEXT

Splenic diffuse red-pulp small B-cell lymphoma is a rare disease, representing less than 1% of all non-Hodgkin lymphomas (NHL). This entity is characterized by involvement of bone marrow sinusoids and peripheral blood. The majority of cases are at an advanced stage when diagnosed. Its pathogenesis is still poorly understood.

CASE REPORTS

We report on two patients with chronic non-replicating hepatitis B virus (HBV) who developed splenic diffuse red-pulp small B-cell lymphoma. Both of them were in stage IV at diagnosis and evolved with aggressive disease. Both of them achieved a complete response through chemotherapy, but one of them died due to infectious complications during bone marrow transplantation. The other decided not to undergo transplantation and continues not to show any evidence of disease today (three years after treatment). Some studies have shown a possible association between B-cell NHL and HBV. Nonetheless, the mechanism through which this oncogenic virus interacts with B-cell NHL is still poorly understood. HBV is lymphotropic and may insert into the host's genome, thus causing overexpression of oncogenes and downregulation of tumor suppressor genes. Therefore, chronic stimulation by HBV can increase B-cell proliferation, which promotes monoclonal expansion of these cells and results in malignancy.

CONCLUSION

HBV may be implicated in the pathogenesis of this lymphoma, although no direct association between these two entities could be proved in the present study. Further investigations are necessary.

Splenic diffuse red pulp lymphoma has a distinct pattern of somatic mutations amongst B-cell malignancies

Splenic Diffuse Red Pulp Lymphoma (SDRPL) has been recently introduced as a provisional entity but differential diagnosis with other splenic lymphomas is needed to be clarified since the therapeutic approaches are distinct. Recently described recurrent mutations or CD180 expression appear useful for differential diagnosis. We completed our previous description in a larger cohort including 53 patients selected on the presence of characteristic villous cells in peripheral blood (PB) and a specific immunophenotype. Immunoglobulin heavy variable (IGHV), BRAF, MYD88, and NOTCH2 mutations were determined and CD180 and BRAF expressions were assessed. Most cases (79%) were IGHV mutated with an overrepresentation of IGHV3-23 (19%) and IGHV4-34 (21%). MYD88 L265P and NOTCH2 mutations were observed in one case each, whereas no BRAF V600E mutation or expression was found. All cases demonstrated a high CD180 expression. Those results strengthen the concept that SDRPL does emerge as a new lymphoma entity distinct from the other splenic lymphomas with circulating lymphocytes.

Issues in diagnosis of small B cell lymphoid neoplasms involving the bone marrow and peripheral blood. Report on the Bone Marrow Workshop of the XVIIth meeting of the European Association for Haematopathology and the Society for Hematopathology

Small B cell lymphoid neoplasms are the most common lymphoproliferative disorders involving peripheral blood (PB) and bone marrow (BM). The Bone Marrow Workshop (BMW) organized by the European Bone Marrow Working Group (EBMWG) of the European Association for Haematopathology (EAHP) during the XVIIth EAHP Meeting in Istanbul, October 2014, was dedicated to discussion of cases illustrating how the recent advances in immunophenotyping, molecular techniques and cytogenetics provide better understanding and classification of these entities. Submitted cases were grouped into following categories: (i) cases illustrating diagnostic difficulties in chronic lymphocytic leukaemia (CLL); (ii) cases of BM manifestations of small B cell lymphoid neoplasms other than CLL; (iii) transformation of small B cell lymphoid neoplasms in the BM; and (iv) multiclonality and composite lymphomas in the BM. This report summarizes presented cases and conclusions of the BMW and provides practical recommendations for classification of the BM manifestations of small B cell lymphoid neoplasms based on the current state of knowledge.

A Single-center Experience in Splenic Diffuse Red Pulp Lymphoma Diagnosis

The World Health Organization 2008 classification highlighted a new nosology-splenic diffuse red pulp lymphoma (SDRPL) with clinical and laboratory features similar to both splenic marginal zone lymphoma and hairy cell leukemia (HCL) and variant form of HCL. Experience of hematologists on the diagnosis and differential diagnosis of SDRPL is extremely limited. The aim of our report was to characterize the clinical and immunomorphologic features of SDRPL on our own observations. During 2013-2014, in National Research Center for Hematology, 87 spleen specimens removed from various B-cell lymphomas were analyzed. In four (4.6%) cases, the diagnosis SDRPL was made based on morphologic, immunohistochemical, immunophenotypic, molecular examination of spleen biopsies, blood and bone marrow samples. In all cases of SDRPL were observed significant splenomegaly, lymphocytosis from 56% to 94% (in two cases with leukocytosis 55.000 and 75.000 109/l). The circulating "villous" lymphocytes phenotype was CD20+ (bright), CD11c+/±, CD103 (weakly)+/±, LAIR-1+, CD25-, CD5-, CD10-, and CD23-. Mutation BRAFV600E was not detected. Bone marrow with minor lymphoid CD20+, CD25-, Annexin1-, Cyclin D1- cell infiltration. The average weight of the spleen was 3900 g (1450-9500 g), and morphologically, there was revealed lymphoid infiltration of red pulp with phenotype CD20+, DBA.44+, CD25-, Annexin1-, Cyclin D1-, CD103-, CD123-, CD27-, focal SD11c± and TRAP±. Now patients are observed in remission: two patients after splenectomy, two after splenectomy and cladribine+rituximab chemotherapy. SRDPL-a rare lymphoma that is suspected in the cases with significant splenomegaly and lymphocytosis with villous lymphocytes forms that have only a part of the classic markers HCL, with minor bone marrow infiltration. The standard diagnosis and treatment is splenectomy. Differential diagnosis of SMZL and HCL has clear criteria, but criteria of differentiation with variant HCL are still unknown.

[Experience in investigating splenic red pulp lymphoma]

AIM

To generalize hematologists' experience of the diagnosis and differential diagnosis of splenic red pulp lymphoma (SRPL).

MATERIAL AND METHODS

Eighty-seven splenic biopsy specimens taken from patients with different B-cell lymphoproliferative diseases were examined in the Hematology Research Center in 2013-2014. The diagnosis of SRPL was based on the morphological, immunohistochemical, immunophenotypic, and molecular examinations of the splenic biopsy specimens, blood and bone marrow (BM) tests in 4 (4.6%) cases.

RESULTS

There was significant splenomegaly in all SRPL cases, lymphocytosis in 56 to 94% (leukocytes, 55 and 75·109/l in 2 cases), circulation of hairy lymphocytes with the phenotypes CD20+ (markedly), CD11c+/±, CD103+/± (weakly), LAIR-1+, CD25-, CD5-, CD10-, and CD23-, which did not contain tartate-resistant acid phosphatase, without BRAFV600E mutation, BM with insignificant lymphoid infiltration of CD20+, CD25-, Annexin 1-, and Cyclin D1-. The weight of the spleen averaged 3900 g (1450-9500 g); its tissue exhibited lymphoid infiltration of the red pulp with the phenotypes CD20+, DBA.44+, CD25-, Annexin1-, Cyclin D1-, CD103-, CD123-, CD27-, focal СD11c±, and TRAP±. Four patients (2 after splenectomy (SE) and 2 after SE and chemotherapy with cladribine and rituximab) are being followed up in remission.

CONCLUSION

SRPL is a rare disease that should be presumed to be in significant splenomegaly and lymphocytosis with hairy lymphocytes, which have only some markers for classical hairy cell leukemia (HCL), in minor BM lesion. SE is the standard for diagnosis and treatment. The differential diagnosis of SRPL with HCL has clear criteria and that with HCL-v is undetected.

Bone marrow and splenic histology in hairy cell leukaemia

Hairy cell leukaemia is a rare chronic neoplastic B-cell lymphoproliferation that characteristically involves blood, bone marrow and spleen with liver, lymph node and skin less commonly involved. Histologically, the cells have a characteristic appearance with pale/clear cytoplasm and round or reniform nuclei. In the spleen, the infiltrate involves the red pulp and is frequently associated with areas of haemorrhage (blood lakes). The cells stain for B-cell related antigens as well as with antibodies against tartrate-resistant acid phosphatase, DBA44 (CD72), CD11c, CD25, CD103, CD123, cyclin D1 and annexin A1. Mutation of BRAF -V600E is present and antibody to the mutant protein can be used as a specific marker. Bone marrow biopsy is essential in the initial assessment of disease as the bone marrow may be inaspirable or unrepresentative of degree of marrow infiltration as a result of the tumour associated fibrosis preventing aspiration of the tumour cell component. Bone marrow biopsy is important in the assessment of therapy response but in this context staining for CD11c and Annexin A1 is not helpful as they are also markers of myeloid lineage and identification of low level infiltration may be obscured. In this context staining for CD20 may be used in conjunction with morphological assessment and staining of serial sections for cyclin D1 and DBA44 to identify subtle residual infiltration. Staining for CD79a and CD19 is not recommended as these antibodies will identify plasma cells and can lead to over-estimation of disease. Staining for CD20 should not be used in patients following with anti-CD20 based treatments. Down regulation of cyclin D1 and CD25 has been reported in patients following BRAF inhibitor therapy and assessment of these antigens should not be used in this context. Histologically, hairy cell leukaemia needs to be distinguished from other B-cell lymphoproliferations associated with splenomegaly including splenic marginal zone lymphoma, splenic diffuse red pulp small B-cell lymphoma and hairy cell leukaemia variant. This can be done by assessment of the spleen but as this is now rarely performed in this disorder distinction is almost always possible by a combination of morphological and immunophenotypic studies on bone marrow trephine biopsy, which can be supplemented by assessment of BRAF-V600E mutation assessment in borderline cases.

MYD88 L265P mutation analysis helps define nodal lymphoplasmacytic lymphoma

The diagnosis of lymphoplasmacytic lymphoma is often challenging, especially in extramedullary tissues where the differential diagnosis includes nodal marginal zone lymphoma, splenic marginal zone lymphoma, or other small B-cell neoplasms with plasmacytic differentiation. The MYD88 L265P mutation has been recently identified in >90% of bone-marrow-based lymphoplasmacytic lymphoma, but the incidence of this abnormality and corresponding morphologic correlates in nodal lymphoplasmacytic lymphoma have not been established. We analyzed 87 cases of extramedullary lymphoplasmacytic lymphoma, splenic marginal zone lymphoma, unclassifiable splenic B-cell lymphomas, nodal marginal zone lymphoma with plasmacytic differentiation, and chronic lymphocytic leukemia/small lymphocytic lymphoma with plasmacytic differentiation for MYD88 L265P. Eighteen cases (21%) were positive, including 9/9 (100%) lymphoplasmacytic lymphomas with classic histologic features, 5/12 (42%) cases that met 2008 WHO criteria for lymphoplasmacytic lymphoma but with atypical morphologic features, 3/15 (20%) cases initially considered nodal marginal zone lymphoma with plasmacytic differentiation, and 1/6 (17%) unclassifiable splenic B-cell lymphomas. The presence of MYD88 L265P was associated with IgM paraprotein (P<0.001) and a trend for bone marrow involvement (P=0.09). Each of 44 splenectomy-defined splenic marginal zone lymphomas (19 with plasmacytic differentiation) and the chronic lymphocytic leukemia/small lymphocytic lymphoma with plasmacytic differentiation were negative for the mutation. Morphologic re-review with knowledge of MYD88 mutation status and all available clinical features suggested all MYD88 mutated cases were consistent with lymphoplasmacytic lymphoma (either classic or variant histology), except for one case which remained most consistent with nodal marginal zone lymphoma with plasmacytic differentiation. These results demonstrate the importance of MYD88 mutational analysis in better defining lymphoplasmacytic lymphoma as a relatively monomorphic small B-cell lymphoma with plasmacytic differentiation that may show total nodal architectural effacement and follicular colonization. Cases previously considered lymphoplasmacytic lymphoma that are more polymorphous and are often associated with histiocytes should no longer be included in the lymphoplasmacytic lymphoma category. Clinicopathologic review suggests that although MYD88 mutated non-lymphoplasmacytic lymphoma small B-cell neoplasms exist, they are very uncommon.

Diagnosis of Splenic B-Cell Lymphomas in the Bone Marrow: A Review of Histopathologic, Immunophenotypic, and Genetic Findings

Splenic B-cell lymphomas are a heterogeneous group of diseases comprising several entities that exhibit overlapping features. Diagnosis of these lymphomas has been reliant on the histopathologic examination of the spleen. However, with advances in diagnostic modalities and therapy, splenectomy is not commonly performed, and diagnosis and subclassification must be rendered based on the blood and bone marrow findings. In this brief review, we summarize the morphologic, immunophenotypic, and genetic findings of splenic B-cell lymphomas in the blood and bone marrow.

[Molecular and therapeutic advances in Hairy cell leukemia]

Hairy cell leukemia is a rare chronic lymphoproliferative disorder. Its diagnosis remains difficult due to different variant forms and differential diagnosis that are splenic marginal zone lymphoma and b-prolymphocytic leukemia. The prognosis of this malignancy has been transformed by purine nucleoside analogs, interferon, monoclonal antibodies and recombinant immunotoxins usually used in refractory or relapsed disease. The discovery of BRAF V600E mutation has become the milestone in the disease's history since it was uniformly identified in a HCL series in 2011. This mutation, commonly identified in melanoma, involves the protooncogene BRAF, a MAP3Kinase belonging to the RAF-MEK-ERK signaling pathway, which is the central key in several oncogenic processes. This mutation suggests disease-specific oncogene dependence. The detection of this mutation provides an additional diagnosis marker (because not found in variant forms), a best for monitoring minimal residual disease and a therapeutic target with the BRAF inhibitors in specific subgroups of patients, already tested in melanoma. This review aims to summarize the clinical and biological aspects and treatment of hairy cell leukemia and discusses the perspectives provided by the discovery of BRAF mutation in this disease.

Focal splenic lesions: US findings

Ultrasound (US) imaging of the spleen was considered of little use in the past and was performed only to distinguish between cystic and solid lesions. However, in the last decade due to experience acquired and the introduction of second-generation contrast agents, this technique has been re-evaluated as contrast-enhanced US (CEUS) allows detection and characterization of most focal lesions of the spleen with a high sensitivity and a good specificity. Gray-scale US presents a low specificity in splenic infarctions with a high rate of false negative cases, whereas specificity reaches 100 %, if the examination is performed using US contrast agents. Gray-scale US can provide a correct diagnosis in simple cysts, whereas CEUS is useful when cystic lymphangioma is suspected. In the study of splenic lesions, the most important problem is to differentiate between angioma, hamartoma, lymphoma, and metastasis. CEUS reaches a good specificity in the differentiation of benign from malignant splenic lesions, as hypo-enhancement in the parenchymal phase is predictive of malignancy in 87 % of cases. In conclusion, Gray-scale US and particularly CEUS are at present widely indicated in the study of focal splenic lesions.

Malignant lymphoma of the spleen in Japan: a clinicopathological analysis of 115 cases

Primary splenic lymphoma is rare, but malignant lymphoma often produces a lesion in the spleen as part of systemic disease. The frequency of splenic malignant lymphoma in Japan is unknown. We classified 184 specimens of the spleen according to the World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues, 4th edition (2008). Of the 184 specimens, 115 were determined to be lymphoid neoplasm (62.5%). The most common subtype of lymphoid neoplasm was diffuse large B-cell lymphoma (DLBCL) (46 cases), followed by splenic marginal zone lymphoma (SMZL) (28 cases), follicular lymphoma (11 cases), splenic B-cell lymphoma, unclassifiable (SBL-U) (6 cases) and peripheral T-cell lymphoma, not otherwise specified (4 cases). In the SBL-U subtype, 5 of 6 cases were splenic diffuse red pulp small B-cell lymphoma, and one case was the hairy cell leukemia variant. Analysis of clinical features revealed that patients with DLBCL had a higher age, high lactate dehydrogenase and tumor formation in the spleen. On the other hand, it was found that patients with SMZL had splenomegaly but no discrete tumor formation. Most of the patients with SBL-U presented with thrombocytopenia, bone marrow involvement, and advanced stage. Our study revealed the frequency and clinical features of splenic malignant lymphoma in Japan.

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.

Revised guidelines for the diagnosis and management of hairy cell leukaemia and hairy cell leukaemia variant*

The British Committee for Standards in Haematology first produced guidelines for the diagnosis and management of hairy cell leukaemia and hairy cell leukaemia variant in 2000. This revision updates those guidelines and covers the areas of diagnosis, treatment and assessment of response to therapy.

[Splenic marginal zone B-cell lymphoma with epidermotropic skin involvement]

Marginal zone B-cell lymphoma (MZL) is subclassified into extranodal MZL of mucosa-associated lymphoid tissue (including cutaneous lymphomas), splenic MZL, and nodal MZL. We report the case of a 68-year-old man with erythematous-violaceous plaques and nodules. Skin biopsy showed an epidermotropic lymphocytic infiltration and cytology and immunohistochemistry were consistent with MZL. The workup revealed disease in the peripheral blood and bone marrow and massive splenomegaly. Splenectomy confirmed the diagnosis of splenic MZL and led to resolution of the skin lesions. Cutaneous recurrence was treated successfully with chemotherapy and rituximab but caused fatal hepatitis due to hepatitis B virus reactivation. Skin involvement by splenic MZL is uncommon; this form of the disease can present epidermotropism, a very rare finding in primary cutaneous MZL. Treatment consists of splenectomy, which may be associated with chemotherapy and/or rituximab; this treatment may lead to reactivation of latent hepatitis B infection and screening for hepatitis should therefore be performed prior to starting therapy.

Sonography of the spleen

This pictorial essay will review and discuss the aspects of differential diagnosis with splenic sonography, including recent literature and exemplary pictorial sonographic cases. Although the spleen is well evaluated by computed tomography and magnetic resonance imaging, sonography has certain advantages, including its ubiquitous availability, lack of ionizing radiation, and low cost. Sonography of the spleen plays an important role in emergency diagnosis of splenic rupture and hemorrhage. The additional use of contrast-enhanced sonography can improve the diagnostic validity. Depending on the indication, sonography of the spleen is especially important for oncologic differential diagnosis of focal lesions, follow-up examinations, and image guidance of therapeutic interventions.

Marginal zone lymphomas with plasmacytic differentiation and related disorders

Marginal zone lymphomas of all types (nodal, splenic, and extranodal mucosa-associated lymphoid tissue [MALT]) may show plasmacytic differentiation. Distinguishing marginal zone lymphomas from other small B-cell lymphomas with plasmacytic differentiation, especially lymphoplasmacytic lymphoma, or from plasma cell neoplasms may be challenging. Marginal zone lymphomas with plasmacytic differentiation were discussed in 2 sessions of the 2009 Society for Hematopathology/European Association for Haematopathology Workshop. Session 4 focused on nodal marginal zone lymphomas, including cases exhibiting classic features and cases displaying atypical phenotypes. The difficulties of classification of cases with increased numbers of large cells were also discussed. Session 5 examined nonnodal marginal zone lymphomas and related entities, including splenic marginal zone lymphoma, MALT lymphoma, γ heavy chain disease, and cryoglobulin-associated lymphoproliferative disorders. These cases illustrate the importance of clinical data and, in some cases, phenotypic and cytogenetic findings in appropriately applying the 2008 World Health Organization criteria.

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.

[Lymphomas of the spleen]

The spleen is commonly affected by malignant lymphomas and the macroscopic findings of the spleen correlate with different lymphoma entities. However, most lymphomas are not primarily diagnosed in splenectomy specimens. Exceptions include splenic marginal zone lymphomas and hepatosplenic T-cell lymphomas that are typically diagnosed from histological findings. In addition, hairy-cell leukemia, LGL leukemia and T-cell prolymphocytic leukemia typically show characteristic patterns of infiltration in the spleen which may be diagnostically useful. The different infiltration patterns of these tumors are discussed here.

[Splenic marginal zone B cell lymphomas]

Splenic marginal zone B cell lymphomas (SMZBCL) are rare, organotypic, lymphoid neoplasms with distinct clinicopathological features. At initial presentation, the spleen, bone marrow and peripheral blood are usually involved, while generalized lymphadenopathy is only rarely observed. Molecularly, somatic hypermutation of IgVH genes can be detected in roughly half of the cases, and deletions in 7q are present in 45% of tumors. Approximately 10%-15% of SMZBCL do occur in the setting of chronic hepatitis C. This association underlines the importance of antigenic stimulation in the proliferation of the tumor cells in HCV-associated SMBCL, if not also in their classical counterparts. More recently, gene profiling studies using cDNA microarrays revealed a homogeneous expression profile in SMZBCL, thus further confirming the notion of a distinct tumor entity. The clinical course is indolent in the majority of cases; however, some patients follow a more aggressive clinical course, usually associated with some particular molecular features in these tumors, such as unmutated IgVH genes and 7q deletions.

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.

Hairy Cell Leukemia: Diagnostic Pathology

The pathology of HCL has been reviewed with a focus on the diagnostic hematopathology of this rare, but fascinating, disease. The discrimination of HCL from other B-cell lymphoproliferations, particularly HCL-V and SMZL, has been emphasized. The unique responsiveness of HCL to 2-CdA and other chemotherapeutic agents makes this distinction critical. Fortunately, HCL has consistent cytologic, histologic, cytochemical, and immunologic features that make classification reliable and reproducible. Less straightforward is the differential diagnosis of SMZL and HCL-V, problematic because of the rarity of both disorders, lack of discriminating evidence-based criteria, and perhaps a biologic kinship between these two disorders that share many clinical and pathologic features. Fortunately, this is not a clinically critical distinction.

Splenic small B-cell lymphoma with IGH/BCL3 translocation

Isolated chromosomal translocations are important defining features of many non-Hodgkin lymphomas, especially of B-cell type. In contrast to some other translocations, the significance of IGH/BCL3 translocations is not well defined. Although often considered a feature of the ill-defined entity atypical chronic lymphocytic leukemia, very few cases are reported in which involvement of BCL3 and the precise B-cell neoplasm are both well documented. For this reason, we report a splenic-based CD5(-), CD10(-), CD43(-), CD23(-), CD103(-), FMC7(+), CD25(+) small B-cell lymphoma associated with epithelioid histiocyte clusters and a t(14;19)(q32;q13) representing an IGH/BCL3 translocation based on classical cytogenetic studies, chromosomal painting, and fluorescence in situ hybridization studies. The previously reported neoplasms with t(14;19)(q32;q13) or IGH/BCL3 translocations are also reviewed. The present case did not fall into any of the classic B-cell lymphoma categories and clearly did not represent chronic lymphocytic leukemia/small lymphocytic lymphoma. This case suggests that the IGH/BCL3 translocation may help to define a new clinicopathologic entity.

Nodal and splenic marginal zone B cell lymphomas

Splenic marginal zone lymphoma (SMZL) and nodal marginal zone lymphoma (NMZL) are newly defined, separate clinicopathological entities. Both are rare lymphoma types, with low reproducibility in the diagnosis, although a conjunction of molecular and clinical studies seems to be now facilitating a more accurate diagnosis and understanding of the neoplastic process. SMZL is a disease involving the spleen, bone marrow and peripheral blood since the initial manifestations of the disease. The diagnosis has been until very recently based on the pathological study of the spleen with the conjunction of the clinical features, although the integration of the morphology in bone marrow and peripheral blood with the immunophenotype and molecular characteristics of the tumour makes a more accurate diagnosis now possible. The most frequent molecular alteration found in SMZL is allelic loss at the 7q chromosomal region. SMZL is an indolent lymphoma, although there is small subset of patients in which it follows an aggressive course. Molecular studies of SMZL are starting to reveal new diagnostic and prognostic markers, and to identify new potentially useful therapeutic targets. Nodal marginal zone lymphoma is a B-cell neoplasm originated in the lymph node, whose histology resembles the nodal infiltration by MALT- or Splenic-type marginal zone lymphoma, in the absence of clinical evidence of extranodal or spleen disease. The lack of characteristic phenotypic or molecular diagnostic findings is still hampering the reproducibility of this diagnosis. Here we review the main morphological and immunophenotypical markers, discussing the differential with other overlapping entities, singularly follicular lymphoma. Specific therapeutic protocols and prognostic factors are required to more precisely define this tumour.

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.

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 marginal-zone lymphoma: a distinct clinical and pathological entity

In the World Health Organization classification system, splenic marginal-zone lymphoma (splenic MZL) is described as an indolent B-cell lymphoma, which generally presents as splenomegaly with involvement of the bone marrow and peripheral blood. Presence of disease in peripheral lymph nodes and extranodal locations is uncommon. Splenic MZL is characterised by micronodular infiltration of the spleen with marginal-zone differentiation; the immunophenotype is usually IgM+ IgD+/- cytoplasmic-Ig-/+ pan B antigens+ CD5- CD10- CD23- CD43-/+ cyclin D1-; and the most common genetic abnormalities are deletions at 7q22-7q32. Most patients with splenic MZL live for a long time but classic prognostic factors cannot distinguish between patients who are likely to have good and poor outcomes. However, immunological events, such as haemolytic anaemia and immune thrombocytopenia, or the presence of a monoclonal component, are significantly associated with shorter survival. Splenectomy is considered the first-line treatment of choice for splenic MZL; it results in only partial remission, but responses are generally sufficient for correcting cytopenia, improving quality of life, and increasing survival.