Monocytoid B-cell Research Articles

Nodal reactive proliferation of monocytoid B-cells may represent atypical memory B-cells.

Reactive lymphadenopathies such as toxoplasmosis and cytomegalovirus lymphadenitis are associated with monocytoid cell proliferation. Monocytoid cells are B-lymphocytes with an undetermined subset. Using digital spatial profiling whole transcriptome analyses, this study compared monocytoid and control B-cells. The B-cell subset of monocytoid cells was assigned according to gene expression profiles. This study identified 466 differentially expressed genes between monocytoid and control B-cells. The cellular deconvolution algorithm identified monocytoid cells as memory B-cells instead of as naïve B-cells. A comparison of the upregulated genes revealed that atypical memory B-cells had the largest number of genes overlapping with monocytoid cells compared with other memory B-cell subsets. Atypical memory B-cell markers, namely TBX21 (T-bet), FCRL4 (IRTA1), and ITGAX (CD11c), were all upregulated in monocytoid cells. Similar to atypical memory B-cells, monocytoid cells exhibited (1) upregulated transcription factors (TBX21, TOX), (2) upregulated genes associated with B-cell inhibition (FCRL5, FCRL4) and downregulated genes associated with B-cell activation (PIK3CG, NFKB1A, CD40), (3) downregulated cell cycle-related genes (CDK6, MYC), and (4) downregulated cytokine receptors (IL4R). This study also analyzed the expression of monocytoid cell signature genes in various memory B-cell subsets. Atypical memory B-cells exhibited a gene expression pattern similar to that of monocytoid cells, but other memory B-cell subsets did not. Furthermore, monocytoid cells and marginal zone lymphomas differed in gene expression profiles. Spatial transcriptomic analyses indicated that monocytoid cells may be atypical memory B-cells.

B Lymphoproliferative Neoplasms of Uncertain Biological Significance: Report from the IV Workshop of the Italian Group of Hematopathology and Review of the Literature

Lymphoproliferative neoplasms of uncertain biological significance are increasingly encountered due to widespread usage of immunophenotypic and molecular techniques. Considering that clearer biological criteria and patient management have been established for B-cell lymphoproliferative diseases of undetermined significance occurring in the peripheral blood, many issues are still obscure for early lesions detected in lymphoid tissues. Regardless that some categories of lymphoproliferative neoplasms of uncertain biological significance have been recognized by the 4th edition of the WHO, other anecdotal early lymphoproliferative lesions still remain fully undefined. Some early lesions frequently originate from the germinal center, including atypical germinal centers BCL2-negative, an early pattern of large B-cell lymphoma with IRF4 rearrangement, and “in situ” high-grade B lymphomas. Moreover, other early lymphoproliferative lesions arise outside the germinal center and include those developing within the setting of monocytoid B-cell hyperplasia, but they also can be directly or indirectly associated with chronic inflammations. This review aims to summarize the concepts discussed during the IV Workshop organized by the Italian Group of Hematopathology, focus on the state-of-the-art on B-cell lymphoproliferative neoplasms of uncertain biological significance, and offer operative insights to pathologists and clinicians in routine diagnostics.

Characterization of molecular genetics and clinicopathology in thymic MALT lymphoma

Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) lymphoma is a type of low-grade malignant B-cell lymphoma. The aim of this study was to investigate the clinicopathological characteristics of thymic MALT lymphoma. We analyzed the clinical, morphological, immunophenotypical, cytogenetic, and molecular characteristics of 11 cases of thymic MALT lymphoma. The relevant literature was also reviewed. The median age of the 11 patients was 50 (range: 33-60). There was a female predominance with a female-to-male ratio of 10:1. Three patients presented with Sjögren syndrome, autoimmune thrombocytopenia purpura, and type B1 thymoma, respectively. Microscopically, thymic MALT lymphoma was characterized by epithelium-lined cysts that were surrounded by small lymphocytes, centrocyte-like cells, and monocytoid B-cells. Plasmacytic differentiation was observed in two cases. The tumor cells expressed CD20, CD79α, and BCL2. Clonal immunoglobulin genes were detected in all 8 examined cases. Fluorescence in situ hybridization (FISH) for 18q21 was performed in 7 cases, and no translocations involving 18q21 were found. Targeted gene sequencing was performed in five cases with available DNA samples, and TNFAIP3, CARD11, IGLL5, and CCND3 mutations were identified. Thymic MALT lymphoma is a rare type of B cell malignancy with a female predominance and excellent clinical outcomes. Molecular aberrations involving the NF-κB pathway are frequent in thymic MALT lymphoma, suggesting that dysregulation of the NF-κB pathway is an important mechanism underlying the pathogenesis of thymic MALT lymphoma.

Clinicopathologic features of primary hepatic marginal zone lymphoma of mucosa-associated lymphoid tissue and hepatic pseudolymphoma

Objective: To study the clinicopathological features of primary hepatic extranodal marginal zone lymphoma of mucosa associated lymphoid tissue (MALT lymphoma) and hepatic pseudolymphoma, and to discuss their differential diagnosis, treatment and prognosis. Methods: Three primary hepatic MALT lymphomas and two hepatic pseudolymphomas collected from January 2012 to March 2017 in the First Affiliated Hospital of Nanjing Medical University were evaluated by HE and immunohistochemistry(IHC), in-situ hybridization and immunoglobulin (Ig) gene rearrangement detection, and the relevant literature reviewed. Results: In the three MALT lymphomas, tumor cells infiltrated the portal areas with nodular pattern, and invaded the surrounding normal liver with serpiginous configuration and formation of confluent sheets. A number of bile ducts were entrapped within the lesions, and showed lymphoepithelial lesion. Reactive lymphoid follicles were present and surrounded by tumor cells, consisting of predominantly centrocyte-like cells and monocytoid B cells. There were clusters of epithelioid histiocytes in one case. The tumor cells were positive for CD20, PAX5 and negative for CD5, CD23, CD10, bcl-6, and cyclin D1. In the two hepatic pseudolymphomas, the lesions presented as solitary nodules well-demarcated from the surrounding liver tissue; one case was partially encapsulated with fibrous tissue. Entrapped bile ducts were only found at the edge of the lesions without lymphoepithelial lesion. The lesions comprised of massive lymphoid proliferation consisting predominantly of reactive lymphoid follicles, but not monocytoid B-cells or atypical cells. By IHC, a mixture of B- and T-cell population was identified. A monoclonal rearrangement of the Ig gene was detected in all three MALT lymphomas but not in two pseudolymphomas. Interphase fluorescence in situ hybridiazation test for MALT1 break-apart gene was positive in two cases of MALT lymphomas and EBER was negative in all studied cases. Conclusions: Primary heptic MALT lymphoma and pseudolymphoma are both rare lymphoid proliferative lesions of liver. These two lesions have overlapping histological and IHC features and are top differential diagnosis to each other. A combination analysis of morphology, immunophenotype and Ig gene rearrangement is helpful to distinguish between them.

Marginal zone B-cell lymphoma of the pulmonary mucosa-associated lymphoid tissue: A case report.

Marginal zone B-cell lymphoma of the pulmonary mucosa-associated lymphoid tissue (pulmonary MALT-MZL) is a common type of primary pulmonary lymphoma, but is rare as a pulmonary malignant tumor. In the present study, a 49-year-old male patient was admitted to The First Affiliated Hospital of Xi'an JiaTong University (Xi'an, China) with a pulmonary lesion in the right upper lung. The patient was diagnosed with pulmonary MALT-MZL subsequent to undergoing chest computed tomography (CT), a routine blood test, pathological and histological examinations, a transbronchial lung biopsy and bronchoscopy. A chest CT scan revealed right middle lobe consolidation and inflammatory signs, accompanied by mediastinal lymphadenopathy in the anterior basal segment of the upper lobe and CT angiogram signs. Bronchial stenosis and swollen mucosa were observed by bronchoscopy. The tissue section of the transbronchial lung biopsy specimens revealed diffusely infiltrated monocytoid B-cell lymphocytes and a lymphoepithelial lesion. The tissue was found to be positive for cluster of differentiation (CD)20, B-cell lymphoma 2 and CD79a expression, but negative for CD3, CD5, cyclin D1 and κ-light chain expression. CD21 and CD23, located in the residual follicular dendritic cells, were detected by immunohistochemical staining. The clinical manifestations of pulmonary MALT-MZL are non-specific and misdiagnosis frequently occurs in clinical practice. Therefore, an appropriate invasive biopsy procedure is necessary for early and accurate diagnosis of pulmonary MALT-MZL. Clinical presentation that includes periodic fever and distended bronchi in pulmonary consolidation may indicate a diagnosis of MALT-MZL. Pulmonary MALT-MZL belongs to the category of indolent lymphoma and accurate clinical diagnosis is challenging. The results in the present study may provide additional evidence for the accurate diagnosis of this rare entity.

Unusual initial presentation of herpes simplex virus as inguinal lymphadenopathy.

Genital herpes simplex virus (HSV) infections are a common cause of inguinal lymphadenopathy. However, surgical excision of enlarged inguinal nodes is almost never performed to initially diagnose genital herpes simplex virus, due to the distinct external presentation of genital herpetic vesicles that usually occur with the first symptoms of infection. Therefore, the histologic and immunophenotypic features of HSV-associated inguinal lymphadenopathy are unfamiliar to most pathologists. The current report describes the lymph node pathology of two immunocompetent patients, whose initial HSV diagnosis was established through surgical excision of enlarged inguinal lymph nodes. Histologic examination showed features consistent with viral lymphadenopathy, including florid follicular hyperplasia, monocytoid B-cell hyperplasia, and paracortical hyperplasia without extensive necrosis. Immunohistochemical stains for HSV antigens, using polyclonal anti-HSV I and II antibodies, demonstrate strong immunoreactivity for HSV in a small number of cells in the subcapsular sinuses, especially in areas with monocytoid B-cell hyperplasia. Rare scattered HSV-positive cells also are identified in paracortical areas and germinal centers. We conclude that an initial diagnosis of genital HSV infection may be established by inguinal lymph node biopsy.

Crystal storing histiocytosis associated with marginal zone B-cell lymphoma: A rare initial clinical presentation diagnosed by fine-needle aspiration.

Crystal storing histiocytosis associated with marginal zone B-cell lymphoma: A rare initial clinical presentation diagnosed by fine-needle aspiration.

Extranodal Marginal Zone Lymphoma Presenting within the Meckel Diverticulum as Diverticulitis: A Case Report.

Meckel diverticulum is the most common congenital defect of the gastrointestinal tract. It can be asymptomatic or mimic appendicitis and may be complicated by bleeding, diverticulitis, obstruction, and, rarely, neoplasia. We report the first case of extranodal marginal zone lymphoma occupying a Meckel diverticulum. A 44-year-old man with history of colonic diverticulitis presented to the emergency department for evaluation of acute abdominal pain. Radiography showed enteric obstruction, prompting diagnostic laparoscopy. Above the level of mid-ileum an intact Meckel diverticulum was identified. Microscopy showed extensive infiltration of sheets of small lymphocytes with abundant cytoplasm (monocytoid B-cells) prominently in submucosa and focally transmural involving serosal adipose tissue with multiple reactive germinal centers. The immunostains showed positivity for CD20, BCL-2, and CD43 (weak) and negativity for CD3, CD5, BCL-1, CD10, and BCL-6 in monocytoid B-cells. Fluorescence in situ hybridization studies revealed API2-MALT1 fusion signals consistent with t(11;18)(q21;q21), which confirmed the diagnosis of extranodal marginal zone lymphoma, also known as mucosa associated lymphoid tissue lymphoma.

Fatal Clinical Outcome in a Patient with Sarcoidosis-Lymphoma Syndrome

A 62-year-old female suspected of malignant disease underwent a splenectomy that revealed noncaseating granulomas in the histological specimen. Chest X-ray (CXR) and lung CT scans suggested sarcoidosis stage II. TBLB showed noncaseating granulomas. A diagnosis of sarcoidosis was made. Initially no treatment was needed as partial remission on CXR and normal lung function were observed. During the follow up she underwent open lung biopsy and axillary lymph node biopsy because of radiological progression with presence of CXR opacities imitating metastases and recurrent lymphadenopathy. No malignant cells were found. Spontaneous partial resolution of disseminated changes on the CXR was observed. Because of progressive deterioration in lung function and the clinical course of the disease strongly suggesting the progression of systemic sarcoidosis, the patient was given steroid treatment, which initially resulted in partial remission of pulmonary disseminated changes, peripheral lymphadenopathy and improvement in lung function test. Eight months later severe deterioration in general condition, anaemia, leukocytosis, hypoxemia, massive hepatomegaly and recurrence of general lymphadenopathy along with progression of disseminated changes were found. She died before the final diagnosis was established. Post-mortem examination showed a nodal marginal zone B-cell lymphoma with monocytoid B-cells, according to WHO classification. The malignant cells were found in the jugular, mediastinal, paratracheal, paragastric, paraintestinal and retroperitoneal lymph nodes and they infiltrated the lungs, pleura, liver, thyroid gland and pancreas. No sarcoid granulomas were found in the autopsy.

Nodal reactive and neoplastic proliferation of monocytoid and marginal zone B cells: an immunoarchitectural and molecular study highlighting the relevance of IRTA1 and T‐bet as positive markers

Marginal zone B cells (MZCs) and monocytoid B cells (MBCs) appear to be related lymphoid cells that take part in reactive and neoplastic marginal zone proliferations. These lesions are not yet well characterized, and the aim of this study was to find better diagnostic criteria for them. We analysed 60 nodal lesions with MBC and/or MZC proliferation for their morphological, immunophenotypic, molecular genetic and IG gene rearrangement features. On the basis of the results of the rearrangement assay and immunoglobulin light chain restriction, the lesions were divided into reactive and neoplastic groups. Among the neoplastic lesions, polymorphic and monomorphic subgroups emerged. All reactive lesions had morphological features of the polymorphic subgroup. By immunohistochemistry, IRTA1 and/or T-bet expression was found in all reactive lesions and in 90% of neoplastic lesions. IRTA1 and T-bet are positive markers for the identification of MZC/MBC proliferations, and thus for the diagnosis of nodal marginal zone lymphoma (NMZL). Polymorphic and monomorphic subgroups of NMZL could be distinguished. Most morphological and immunophenotypic patterns in reactive and neoplastic nodal expansions of MZCs and MBCs overlapped. Therefore, PCR clonality assay of the immunoglobulin heavy and light chain gene loci is the most reliable method for their differentiation.

Thymic Hyperplasia With Lymphoepithelial Sialadenitis (LESA)–like Features

Four cases of an unusual type of thymic hyperplasia strongly resembling lymphoepithelial sialadenitis (LESA) of the salivary glands are described. The patients were 2 men and 2 women aged 37 to 53 years. On histologic examination, abundant lymphoid tissue with lymphoid follicles containing germinal centers and areas of plasma cell infiltration were seen. The epithelial component consisted of a proliferation of Hassall corpuscles and islands of thymic epithelial cells. Cystic changes and lymphoepithelial lesions were identified in all cases, but a monocytoid B-cell population was absent. On immunohistochemical examination, a mixed B- and T-cell population was identified, and polymerase chain reaction performed in 1 case showed polyclonality. Follow-up revealed that all patients were alive 5 months to 9 years after diagnosis. The cases in this series represent a distinct type of thymic hyperplasia that histologically strongly resembles LESA. The clinicopathologic and immunohistochemical features are presented, and a possible relationship with thymic mucosa-associated lymphoid tissue (MALT) lymphoma is discussed.

Temporal differences of onset between primary skin lesions and regional lymph node lesions for tularemia in Japan: a clinicopathologic and immunohistochemical study of 19 skin cases and 54 lymph node cases

For tularemia, a zoonosis caused by the gram-negative coccobacillus Francisella tularensis, research of the relation between skin lesions and lymph node lesions has not been reported in the literature. This report describes skin lesions and lymph node lesions and their mutual relation over time for tularemia in Japan. Around the second day after infection (DAI), a subcutaneous abscess was observed (abscess form). Hand and finger skin ulcers formed during the second to the fourth week. Subcutaneous and dermal granulomas were observed with adjacent monocytoid B lymphocytes (MBLs) (abscess–granulomatous form). From the sixth week, large granulomas with central homogeneous lesions emerged diffusely (granulomatous form). On 2–14 DAI, F. tularensis antigen in skin lesions was detected in abscesses. During 7–12 DAI, abscesses with adjacent MBLs appeared without epithelioid granuloma (abscess form) in regional lymph nodes. During the second to fifth week, granulomas appeared with necrosis (abscess–granulomatous form). After the sixth week, large granulomas with a central homogeneous lesion (granulomatous form) appeared. F. tularensis antigen in lymph node lesions was observed in the abscess on 7–92 DAI. Apparently, F. tularensis penetrates the finger skin immediately after contact with infected hares. Subsequently, the primary lesion gradually transfers from skin to regional lymph nodes. The regional lymph node lesions induced by skin lesion are designated as dermatopathic lymphadenopathy. This study revealed temporal differences of onset among the skin and lymph node lesions.

Granulomatous Lymphadenitis

In this review, representative types of granulomatous lymphadenitis (GLA) are described. GLA can be classified as noninfectious GLA and infectious GLA. Noninfectious GLA includes sarcoidosis and sarcoid-like reaction. The cause of sarcoidosis remains unknown, but it has good prognosis. Sarcoid-like reaction, which is considered to be a biological defense mechanism, is observed in regional lymph nodes with many underlying diseases. Infectious GLA can be classified as suppurative lymphadenitis (LA) and nonsuppurative LA. Suppurative LA generally shows follicular hyperplasia and sinus histiocytosis in the early phase. In tularemia and cat scratch disease, monocytoid B lymphocytes (MBLs) with T cells and macrophages contribute to the formation of granuloma. However, none of the epithelioid cell granulomas of Yersinia LA contains MBLs like in cat scratch disease. In addition, almost all have a central abscess in granulomas induced by Gram-negative bacteria. In terms of the lymph nodes, tularemia and cat scratch disease are apt to affect the axillary and cervical regions while Yersinia LA affects the mesenteric lymph node. Nonsuppurative LA includes tuberculosis and BCG-histiocytosis. These are induced by delayed allergic reaction of M. tuberculosis. Tuberculosis LA mainly appears in the cervical lymph node. Organisms are histologically detected by Ziehl-Neelsen staining in the necrotic area. Toxoplasmosis is also a nonsuppurative protozoan infection (Toxoplasma gondii). In toxoplasma LA, MBLs can also be seen, but round and organized, well-formed granulomas are not found in this disease. Furthermore, necrosis is not induced and there are no accompanying neutrophils, eosinophils and fibrosis. GLA described above is associated with characteristic histological findings. An accurate pathological diagnosis using the above findings can lead to precise treatment.

Primary Gastric Plasmacytoma: A Rare Cause of Melena

Purpose: Extramedullary plasmacytomas (EMP) are particularly rare, accounting for less than 3-4% of all plasma cell tumors. Almost 90% of cases with EMP develop in the head and neck area including the sinuses, nasopharynx, and tonsils. We report a case of primary gastric plasmacytoma and its clinical, endoscopic, and histological manifestations. Results: A 52-year-old man with hypertension and dyslipidemia presented with a one week history of melena, fatigue, early satiety, and epigastric discomfort. On upper endoscopy, a 3 cm mass was identified opposite the cardia along the posterior wall of the stomach at the body/fundus junction [Image 1]. On endoscopic ultrasound, a 3.3 cm mass was found in the submucosa of the stomach, with involvement of the muscularis propria [Image 2]. Biopsy specimens of the mass revealed gastric mucosa with a mild to moderate inflammatory infiltrate composed of small lymphocytes with plasma cells. Immunohistochemical stains performed on the neoplastic cells demonstrated the presence of plasma cell marker CD138, monotypic for immunoglobulin kappa light chains. CD20, a B-cell marker, was not expressed by the malignant cells. The morphology of the plasma cells in conjunction with immunohisto-chemistry was consistent with primary gastric plasmacytoma. Marginal zone B-cell lymphoma (MALT) was considered unlikely because of the absence of monocytoid B-cells, CD20 B-cell marker, centrocytes and small lymphoid cells. A bone marrow biopsy showed no evidence of lymphoma or plasma cell neoplasm. Conclusion: Primary gastric plasmacytoma is an extremely rare diagnosis with scattered case reports in the literature. Though no general consensus exists on treatment, radiation therapy and surgical resection are two modalities that have been used.Figure: Mass.Figure: EUS.

Infectious mononucleosis lymphoadenitis showing histologic findings indistinguishable from toxoplasma lymphadenitis. A report of three cases

Lymph node lesions in infectious mononucleosis (IM) show a marked histologic diversity. We report here three cases of IM lymphadenitis with histologic findings indistinguishable from those of toxoplasmic lymphadenitis. The histologic findings of the three cases presented here showed a histologic triad of toxoplasmic lymphadenitis, including (i) numerous lymphoid follicles with hyperplastic germinal centers; (ii) small clusters or single epithelioid histiocytes; and (iii) multiple foci of monocytoid B-cells. Moreover, all three lesions contained isolated or small clusters of epithelioid histiocytes within the hyperplastic germinal centers and the periphery of lymphoid follicles, which are the most specific histologic findings of toxoplasmic lymphadenitis. However, serologic findings confirmed EBV infection in all three cases. On in situ hybridization, numerous Epstein-Barr virus (EBV)-encoded small RNA (EBER)-positive cells were demonstrated in the germinal center, as well as in interfolicular areas in all three cases. Toxoplasmosis gondii infection was excluded in at least one case, based on serologic findings. Polymerase chain reaction analysis also demonstrated that there was no T. gondii DNA in the remaining two cases. Two of our three cases showed atypical clinical presentations, including an absence of atypical lymphocytosis in peripheral blood in two cases, age more than 30 years, and an absence of systemic symptoms in one case. It appears that previous descriptions emphasize the differential diagnostic problems between IM lymphadenitis and malignant lymphomas. However, from a therapeutic perspective, it is important to discriminate IM lymphadenitis from toxoplasmic lymphadenitis particularly in patients showing atypical clinical features.

Interferon-γ and T-bet expression in a patient with toxoplasmic lymphadenopathy

Infection with Toxoplasma gondii ( TG) presents in some individuals as a self-limited disease with a predominant lymphadenopathy characterized by prominent B-cell activation. As this is in contrast to the in vitro based concept of a T h1-immune response against TG, we investigated native lymphoid tissue and peripheral blood of a patient with serologic evidence of toxoplasmosis to verify which cells show T h1-response features. High-level expression of T-bet in monocytoid B-cells, in germinal center B-cells, and in a lesser amount in T cells could be demonstrated by immunohistochemistry. In vitro stimulation of lymph node cells with either TG, staphylococcus enterotoxin B, or phorbol 12-myristate 13-acetate/ionomycin revealed an interferon-γ expression in T-bet + B cells only in the patient and not in controls. Similar results were found for T-bet + T cells which were also present in controls. CD4 + peripheral blood cells stimulated with TG antigens showed a TG-specific but attenuated T h1-reactivity in the patient associated with a reduced expression of IL-2 when compared with controls. We conclude that the pathogenesis and course of toxoplasmic lymphadenopathy is based on a T h1-cell defect, which becomes compensated by the B cells mounting a T h1-like immune response.

T-box-expressed-in-T-cells (T-bet) expression by the tumor cells of hairy cell leukemia correlates with interferon-gamma production

Hairy cell leukemia (HCL) is an uncommon B-cell malignancy with unknown pathogenesis. In an earlier study, we demonstrated that HCL cells highly express the transcription factor T-box-expressed-in-T-cells (T-bet). T-bet is the master regulator of the T-helper (Th)1 cell response regulating interferon gamma (IFN-γ) production and also plays a central role in the T-cell independent Th1-like B-cell response. Here, we demonstrate by fluorescence activated cell sorting (FACS) analysis that neoplastic cells from the peripheral blood of five patients with HCL showed an enhanced expression of IFN-γ after stimulation. Additionally, a comparison with 55 healthy individuals revealed a significant elevation of IFN-γ in the sera of patients with HCL. Based on our recent findings that a non-neoplastic B-cell subset, the monocytoid B-cells, are T-bet positive and produce IFN-γ, we propose that monocytoid and hairy B-cells have a similar function and that the T-bet-IFN-γ axis is involved in the pathogenesis of HCL.

Tonsillar Lesions of Infectious Mononucleosis Resembling MALT Type Lymphoma. A Report of Two Cases

Infectious mononucleosis (IM) is an acute lymphoproliferative disorder that typically occurs in young patients and is usually caused by Epstein-Barr virus. We report here, two cases of tonsillar lesion of IM resembling marginal zone B-cell lymphoma mucosa-associated lymphoid tissue (MALT) type. The patients consisted of an 18-year-old Japanese woman and a 36-year-old Japanese man. Both patients presented with tonsillar mass. Histologically, in one case, the tonsil showed diffuse proliferation of medium-sized lymphocytes. The medium-sized lymphocytes had round or slightly indented nuclei with a small solitary nucleoli and abundant clear cytoplasm and somewhat resembled monocytoid B-cells. In the remaining one case, the lymphoid follicles had hyperplastic germinal centers with ill-defined borders surrounded by a sheet-like proliferation of polymorphous infiltration showing a marginal zone distribution pattern. On high-power field, the interfollicular area was diffusely infiltrated by a polymorphous infiltrate of medium-sized lymphocytes with angulated nuclei somewhat resembling centrocyte-like cells, immunoblasts, plasma cells, plasmacytoid cells and histiocytes with or without epithelioid cell feature. However, there were no CD43+ B-cells in either lesion. Moreover, the polytypic nature of the B-cells was demonstrated by immunohistochemistry or polymerase chain reaction. Although MALT type lymphoma rarely affected young adults, notably, a number of cases have been reported in the tonsil. The present two cases indicated that acute IM should be added to the differential diagnosis for MALT type lymphoma in young adults.

Nodal marginal zone B-cell lymphoma: a clinicopathologic study of 10 cases

To study the morphologic features, immunophenotype, differential diagnosis and prognosis of nodal marginal zone B-cell lymphoma (NMZL). Light microscopic examination and immunohistochemical study were carried out in 10 cases of NMZL. Seven of which had follow-up information available. All cases presented with good performance status at the time of diagnosis. Amongst the 7 cases with follow-up information available, most (6/7) were in advanced clinical stage (stage II to III). The one-year survival rate was 67%. A vaguely nodular growth pattern was observed in most cases of NMZL (5/10). The lymphoma was composed predominantly of atypical lymphoid cells resembling centrocytes (7/10). A predominance of monocytoid B-cell (2/10) or small lymphocytic (1/10) morphology was rare. Instead, the presence of a minor component of monocytoid B cells was not uncommon (5/10). Plasmacytoid or plasmacytic cells were also frequently found (8/10). The proliferation index ranged from 5% to 50%. Follicular dendritic cells appeared atrophic in 7 cases and variably hyperplasic in 3 cases. Primary NMZL is rare. It has a unique growth pattern and most cases are composed predominantly of cells resembling centrocytes. Differential diagnosis includes lymphoplasmacytic lymphoma, lymph node involvement by extranodal marginal zone B-cell lymphoma and T-zone hyperplasia. The clinical stage is often high at presentation, with systemic dissemination. The prognosis of NMZL is thus relatively poor.

Cyclin D1 and t(11;14)-positive B-cell neoplasms resembling marginal zone B-cell lymphoma: a morphological variant of mantle cell lymphoma

We describe 3 unusual B-cell non-Hodgkin's lymphomas in which the entire tumors histologically mimicked marginal zone B-cell lymphoma. All patients were male (mean age, 65 years). Excisional biopsy from lymph node (2 of 3) and parotid gland (1 of 3) showed proliferation of monocytoid B-cells with plasmacytoid features (2 of 3) and conspicuous absence of large lymphoma cells (3 of 3). By immunohistochemistry, cyclin D1 was positive (3 of 3), CD23 was negative (3 of 3), and aberrant expression of CD5/CD43 was present in 1 case. Ki67 labeling was greater than 50% in 1 case and 10% to 25% in the other 2 cases. Evidence of the t(11;14) was detectable in all by molecular techniques. One patient died within 15 months, and the other 2 patients had widely disseminated diseases at the last follow-up (8 months). Based on these features, we believed that the best classification for these lesions is the marginal zone B-cell lymphoma-like mantle cell lymphoma.