Monocytoid B lymphocytes: their relation to the patterns of the acquired immunodeficiency syndrome (AIDS) and AIDS-related lymphadenopathy

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

BACKGROUND

Reactive lymphadenopathies such as toxoplasmosis and cytomegalovirus lymphadenitis are associated with monocytoid cell proliferation. Monocytoid cells are B-lymphocytes with an undetermined subset.

METHODS

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.

RESULTS

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.

CONCLUSION

Spatial transcriptomic analyses indicated that monocytoid cells may be atypical memory B-cells.

A Novel Cytological Model of B-Cell/Macrophage Biphenotypic Cell Hodgkin Lymphoma in Ganp-Transgenic Mice

Hodgkin lymphoma (HL) is one of the most difficult neoplasms in terms of cytopathological research owing to the lack of established cytological murine models. Although HL is believed to be of lymphoid germinal center B-cell origin, HL cells exhibit unique biphenotypic characteristics of B cells and macrophages. B-cell/macrophage biphenotypic cells have also been identified in the spleen of Lyn-deficient mice. Moreover, Lyn-targeting germinal center-associated nuclear protein (GANP)-transgenic mice (Ig-ganp^Tg mice) spontaneously develop a lymphoid tumor. We aimed to investigate whether the lymphoid tumor developed in Ig-ganp^Tg mice exhibit biphenotypic characteristics of B cells/macrophages that correspond to human HL. Here, we demonstrated GANP overexpression in human HL cells and found that it may regulate transdifferentiation between B cells and macrophages. We also demonstrated that tumors were comparable with B-cell/macrophage biphenotypic Hodgkinoid lymphomas. The tumor cells expressed macrophage-related F4/80, CD68, and CD204 as well as cytoplasmic B220 and µ-/κ-chains; in addition, these cells exhibited phagocytic activity. These cells also expressed transcripts of CD30; c-fms; and the cytokines monocyte chemoattractant protein (MCP)-1, MCP-5, RANTES, tumor necrosis factor-α and thrombopoietin associated with macrophages as well as granulocyte/macrophage colony-stimulating factor, interleukin (IL)-4, IL-10, IL-12, and IL-13. Ig-ganp^Tg mice represent a novel cytological model for the study of cytopathological etiology and oncogenesis of HL.

Evolutionary implication of B-1 lineage cells from innate to adaptive immunity

The paradigm that B cells mainly play a central role in adaptive immunity may have to be reevaluated because B-1 lineage cells have been found to exhibit innate-like functions, such as phagocytic and bactericidal activities. Therefore, the evolutionary connection of B-1 lineage cells between innate and adaptive immunities have received much attention. In this review, we summarized various innate-like characteristics of B-1 lineage cells, such as natural antibody production, antigen-presenting function in primary adaptive immunity, and T cell-independent immune responses. These characteristics seem highly conserved between fish B cells and mammalian B-1 cells during vertebrate evolution. We proposed an evolutionary outline of B cells by comparing biological features, including morphology, phenotype, ontogeny, and functional activity between B-1 lineage cells and macrophages or B-2 cells. The B-1 lineage may be a transitional cell type between phagocytic cells (e.g., macrophages) and B-2 cells that functionally connects innate and adaptive immunities. Our discussion would contribute to the understanding on the origination of B cells specialized in adaptive immunity from innate immunity. The results might provide further insight into the evolution of the immune system as a whole.

Lymphoid Proliferations Associated With Human Immunodeficiency Virus Infection

Context.—Individuals who are immune deficient are at an increased risk for developing lymphoproliferative lesions and lymphomas. Human immunodeficiency virus (HIV) infection is 1 of 4 clinical settings associated with immunodeficiency recognized by the World Health Organization (WHO) in which there is an increased incidence of lymphoma and other lymphoproliferative disorders.

Objectives.—To describe the major categories of benign lymphoid proliferations, including progressive HIV-related lymphadenopathy, benign lymphoepithelial cystic lesions, and multicentric Castleman disease, as well as the different types of HIV-related lymphomas as defined by the WHO. The characteristic morphologic, immunophenotypic, and genetic features of the different entities will be discussed in addition to some of the pathogenetic mechanisms.

Data Sources.—The WHO classification of tumors of hematopoietic and lymphoid tissues (2001 and 2008), published literature from PubMed (National Library of Medicine), published textbooks, and primary material from the authors' current and previous institutions.

Conclusions.—HIV infection represents one of the clinical settings recognized by the WHO in which immunodeficiency-related lymphoproliferative disorders may arise. Although most lymphomas that arise in patients with HIV infection are diffuse, aggressive B-cell lesions, other lesions, which are “benign” lymphoid proliferations, may also be associated with significant clinical consequences. These lymphoproliferations, like many other immunodeficiency-associated lymphoproliferative disorders, are often difficult to classify. Studies of HIV-associated lymphoid proliferations will continue to increase our understanding of both the immune system and lymphomagenesis.

Co-ordinated expression of lymphoid and myeloid specific transcription factors during B-1b cell differentiation into mononuclear phagocytes in vitro

We previously demonstrated that B-1b cells can undergo differentiation to acquire a mononuclear phagocyte phenotype upon attachment to substrate in vitro. Here we followed the expression of surface markers and transcription factors during this differentiation. B-1b cells spontaneously express both myeloid and lymphoid restricted transcription factors. When induced to differentiate into a phagocyte, the lymphoid genes E box protein (E2A), early B-cell factor (EBF), paired box 5 (Pax5) are down-modulated, while expression of genes related to myeloid commitment is sustained. Furthermore, B-1b cell-derived phagocytes (B-1CDPs) decrease immunoglobulin M (IgM) expression but retain the expression of the heavy chain variable gene VH11 or VH12, an immunoglobulin gene rearrangement predominantly expressed by B-1 cells. The maintenance of lymphoid characteristics in B-1CDPs characterizes a unique type of phagocyte, not related to monocyte-derived macrophages.

Epstein-Barr Virus Infection of Monocytoid B-Cell Proliferates

Monocytoid cells are a subset of B lymphocytes with characteristic morphology and immunophenotype, which proliferate in a broad variety of reactive lymph node conditions. Up to now, no direct infection of these cells by a pathogenic organism has been identified. We found in a series of lymph node specimens from 13 patients having in common a prominent monocytoid B (MCB)-cell reaction in the absence of epithelioid cells or necrosis evidence that Epstein-Barr virus (EBV) can infect MCB cells. Clinical and serologic findings indicative for an acute EBV infection were reported only in 2 cases. By in situ hybridization and immunohistology, a number of MCB cells in all cases was found to contain EBV-encoded small nuclear RNAs and to express the EBV-encoded nuclear antigen (EBNA)-2 and, in lesser extent, the latent membrane protein-1. EBV-transcripts and proteins were also detectable in a number of extrafollicular B blasts and germinal center B cells in 10 of 13 cases. Our findings imply that an EBV infection of MCB cells associated with predominant EBNA-2 expression represents an early sign of primary infection and that it should be included in the differential diagnosis of activated lymph nodes with prominent MCB-cell reaction in the absence of epithelioid cells.

Biphenotypic B/macrophage cells express COX-1 and up-regulate COX-2 expression and prostaglandin E(2) production in response to pro-inflammatory signals

B/macrophage cells are biphenotypic leukocytes of unknown function that simultaneously express B lymphocyte (IgM, IgD, B220, CD5) and macrophage (phagocytosis, F4/80, Mac-1) characteristics. B/macrophage cells can be generated from purified mouse B lymphocytes incubated in fibroblast-conditioned medium. A potential role for B/macrophage cells in inflammation was shown by their ability to express prostaglandin H synthase-1 (COX-1) and prostaglandin H synthase-2 (COX-2) and by their production of prostaglandin (PG) E(2). COX-1 and COX-2 mRNA expression is not observed in the precursor B lymphocytes and is not known to be a property of B lineage cells. In contrast, COX-2 and the prostanoids PGE(2), PGF(2alpha) and PGD(2) are highly inducible in B/ macrophage cells upon stimulation with lipopolysaccharide, CD40 ligand, or via engagement of surface IgM, supporting a role for these cells in inflammation. PGD(2) and its metabolites are of interest because they activate the nuclear receptor PPARgamma that regulates lipid metabolism. The B/macrophage represents the first instance of a normal B-lineage cell capable of expressing COX-2. Importantly, B/macrophage cells were identified in vivo, providing evidence that they may play a significant role in immune responses. Since PGE(2) blunts IL-12 production, its synthesis by B/macrophage cells may shift the balance of an immune response towards Th2 and humoral immunity.

Fibroblast-Secreted Macrophage Colony-Stimulating Factor Is Responsible for Generation of Biphenotypic B/Macrophage Cells from a Subset of Mouse B Lymphocytes

Normal and malignant CD5+ B lymphocytes can develop macrophage-like characteristics. One stimulus of this phenotypic shift is culture of normal mouse splenic B lymphocytes with splenic fibroblasts or their conditioned media. These biphenotypic B/macrophage (B/Mφ) cells simultaneously display macrophage characteristics, such as phagocytosis and F4/80 expression, while retaining B cell features, including expression of surface Ig, CD5, B220, and rearranged Ig genes. The present study investigated the fibroblast-secreted factor that promotes this phenotypic change from B cell to B/Mφ cell. RT-PCR analysis demonstrated that mRNA for M-CSF is produced by splenic fibroblasts. Recombinant M-CSF (CSF-1) could replace fibroblast-conditioned medium to elicit the development and survival of B/Mφ cells from splenic B lymphocytes. In addition, neutralization of fibroblast-secreted M-CSF with specific mAbs abrogated the ability of conditioned supernatants to promote outgrowth of B/Mφ cells. The transition from B lymphocyte to B/Mφ cell was marked by the kinetic appearance of mRNA for the M-CSF receptor, c-fms, at day 3 following culture initiation. These results demonstrate that M-CSF is important in the development and physiology of mouse B/Mφ cells and potentially in the growth of human biphenotypic hematological malignancies. Interestingly, the presence of IFN-γ in splenic B lymphocyte cultures abrogated the effect of fibroblast-conditioned medium or M-CSF on outgrowth of B/Mφ cells. Furthermore, these findings suggest that a Th1 microenvironment favored by typical macrophages is detrimental to the outgrowth of B/Mφ cells.

Occurrence of monocytoid B-cells in reactive lymph node lesions

Benign monocytoid B-cells are a peculiar subset of B-cells. They are closely related to marginal zone B-lymphocytes, show cytological diversity and may be recognized in a variety of reactive lymph node conditions. To analyze the incidence, cytological spectrum and phenotypic features of benign monocytoid B-cells, we investigated a series of 301 consecutively biopsied and unselected cases of reactive lymph node change from 1988 and 1995. A monocytoid B-cell reaction was identified in 46 (15%) cases and could be cytologically subclassified into two groups: 31 (67%) cases with common-type cells and 15 (33%) cases with large, transformed cells, according to the description by Plank et al. [19]. These reactions were regularly associated with follicular hyperplasia (95%) and were part of an epithelioid cell response in 24 cases (50%). Immunohistologically, both types of benign monocytoid B-cells were negative for bcl-2 protein expression, which was in contrast to the bcl-2 positive reaction in marginal zone B-lymphocytes and their neoplastic counterpart in monocytoid B-cell lymphoma. An association of Epstein-Barr virus (EBV) with monocytoid B-cells was investigated by in situ-hybridization. EBV genomes were detected in five (15%) of 31 cases tested. In each of these five cases, positive cells were represented in both high and low numbers. The morphologic features of the EBV-positive cells were not consistent with monocytoid B-cells, but rather with medium-sized to large lymphoid cells. It appeared that the occurrence of monocytoid B-cell reaction in reactive lymph node lesions was not related to EBV infection in the majority of cases.

Subepithelial B cells in the human palatine tonsil. I. Morphologic, cytochemical and phenotypic characterization

This study describes the purification of a subset of tonsillar B cells which share phenotypic, morphologic and cytochemical features with subepithelial (SE) B cells. These cells, which represented the 5-10% of the total tonsillar B cells, were found in the Percoll gradient fraction of highest density, together with resting follicular mantle (FM) B cells. The latter B cells, however, expressed surface CD5 and could be removed by an immune rosetting procedure. The remaining small CD5- B cells had a surface phenotype (IgM+, IgD+, CD23-, CD38+/-, CD10-, CD44+) that was different from that of FM (IgM+, IgD+, CD23+, CD39+, CD38-, CD10-, CD44+2) and of germinal center (GC) (CD23-, CD39-, CD38+, CD10+, CD44+/-, IgG+) B cells isolated from the same cell suspensions. Furthermore, the absence of surface activation markers (CD71 and CD69) and of surface IgG allowed us to distinguish small CD5- B cells from activated and memory cells migrating within Percoll fractions of lower density. In situ immunohistochemical studies revealed that B cells with an identical phenotype as that of small CD5- B cells could be detected predominantly in the SE region (lamina propria) of the tonsil, and also within the epithelium lining the cryptae. This area was also comprised of a relatively minor proportion of activated B cells, not found in the small CD5- B cell fraction owing to the separation procedure used. Consistent with the notion that the SE area could be a site of B cell activation was also the presence of activated macrophages and of plasma cells. Thirty to forty percent of small CD5- B cells isolated in suspension were positive for the endogeneous alkaline phosphatase (ALP) activity. In contrast, only a few FM B cells were ALP+, while GC cells were consistently ALP-. In situ studies also demonstrated a prevalent expression of ALP activity by the B cells in the SE area. At the ultrastructural level, small CD5- B cells were clearly different from both FM and GC B cells. They displayed a cytoplasm more extended than that of FM B cells with abundant endosomes and plasma membrane projections, and a speckled pattern of nuclear heterochromatin distribution. When fixed tissue sections were examined, cells with identical ultrastructural features could be demonstrated in the tonsillar lamina propria. Collectively, the above data demonstrate an identity of features between the small CD5- B cells isolated in suspension and SE B cells analyzed in situ. Since tonsillar SE B cells are generally thought to represent the homolog of the extrafollicular B cells (including those of the splenic marginal zone), these studies may provide new opportunities for functional studies on this so far incompletely characterized B cell subset.

Monocytoid/marginal zone B-cell differentiation in follicle centre cell lymphoma

We report on two cases of low grade follicle centre cell lymphoma with a pronounced parafollicular monocytoid/ marginal zone B-cell component. One patient had a history of preceeding follicular high grade B-cell lymphoma of centroblastic type showing the same light chain restriction and identical immunoglobulin heavy chain gene rearrangement as the low grade lymphoma diagnosed 15 months later. Morphologically, in both cases the two constituents of the low grade tumours were clearly distinguishable. Immunohistochemically, the follicular component strongly expressed bcl-2 protein in contrast to a weak staining of the marginal zone B-cell component. Performing PCR, a rearrangement of the major breakpoint region of bcl-2 was not found. Identical light chain restriction of the follicular and the monocytoid B-cell/marginal zone components strongly indicates a clonal relationship between them. A monocytoid/marginal zone B-cell component in follicular lymphoma probably results from differentiation of the follicle centre cells and does not indicate a composite lymphoma.

Occurrence of monocytoid B lymphocytes in lymph nodes of patients treated by chemotherapy

Occurrence of monocytoi B lymphocytes (MBL) in the lymph nodes of patients receiving preoperative chemotherapy for cancer was examined and compared to lymph nodes in controls who had not received chemotherapy. Number of patients receiving and not receiving preoperative chemotherapy were 3 and 10 cases in ovarian cancer, 7 and 11 in testicular cancer, and 22 and 8 in lung cancer, respectively. Chemotherapeutic agents for ovarian, testicular, and lung cancer consisted of cisplatin, Adriamycin, and cyclophosphamide; cisplatin, vinblastine, and bleomycin; and cisplatin, vindesin, and mitomycin, respectively. MBL were defined morphologically as having abundant pale cytoplasm with distinct cell borders and small nucleus. Immunohistochemistry revealed a B-cell nature of these cells, i.e., CD20+ and/or MB-1+ together with negative reactivity for antibodies for T lymphocytes (CD43, CD45RO, OPD4) and macrophages (KP-1, PGM-1). Monocytoid cells in two cases showed a positive reactivity for CD43 together with CD20. The occurrence rate of MBL in patients with ovarian, lung, and testicular cancer receiving and not receiving chemotherapy was 67% (2/3) and 10% (1/10), 59% (13/22) and 75% (6/8), and 43% (3/7) and 9% (1/11), respectively. The occurrence rate in the total patients receiving chemotherapy (56%) was significantly higher than for those not receiving chemotherapy (28%) (P < 0.05). These findings suggest that chemotherapy-induced depressed immune function is causative for the occurrence of MBL in the lymph nodes. MBL might be found more frequently in nodes from patients who have received chemotherapy in certain settings.

Monocytoid B-cell reaction associated with peripheral T-cell lymphomas

Benign monocytoid B-cells (MBCs) proliferation was reported to occur in various lymphoproliferative disorders, but not in peripheral T-cell lymphomas (PTCL). In our review of fifty three nodal-based, low and high grade PTCL, MBCs were identified histologically and immunohistochemically in eight of the cases. They included: chronic lymphocytic leukaemia of T-cell type (n = 1) with multiple MBCs clusters, large cell anaplastic lymphoma (n = 1) showing lymphoma cells within multiple MBCs foci, and PTCL of angioimmunoblastic lymphadenopathy (AILD) type (n = 6) with solitary (n = 4) or multifocal (n = 2) MBCs reaction. Progression from AILD-hyperimmune reaction to PTCL of AILD type could be observed in one case by three consecutive follow-up biopsies. While MBCs proliferation associated with hyperimmune reaction was prominent, in PTCL of AILD type only isolated or small multiple clusters of MBCs were present. In PTCL of AILD type, MBCs seemed to be a residual component of a prior hyperimmune reaction diminishing with progress of the disease. Therefore we assume that the development of PTCL of AILD type from preceding hyperimmune reaction is more common than previously considered. Cytologically, MBCs proliferation associated with PTCL shows two cell types, as described in reactive lymphadenopathies: the common type and the large cell type MBCs.

Immunoreactivity of neoplastic and non-neoplastic monocytoid B lymphocytes for DBA.44 and other antibodies

AIMS--To evaluate the immunoreactivities of neoplastic and non-neoplastic monocytoid B cells (MBC) and compare them with hairy cell leukemia (HCL) and mantle cell lymphoma (MCL). METHODS--An immunohistochemical study of paraffin wax embedded sections was done on surgically resected specimens of spleens with MBC clusters from patients with gastric cancer (14 cases), tonsils (five cases), and lymph node (two cases) showing lymphoid follicular hyperplasia (LFH), submandibular lymph nodes containing MBC in Sjögren's syndrome (one case). Extranodal organs affected by MCL (three cases) and monocytoid B cell lymphoma (MBCL) (seven cases), and spleens from HCL (four cases) were also studied. These specimens were fixed in 10% formalin and routinely processed for paraffin wax embedding. Fresh spleen specimens from patients with liver cirrhosis (one case) and gastric cancer (seven cases) were snap frozen. RESULTS--Mantle zone lymphocytes were DBA.44, CD74 positive and showed a weaker reaction for CDw75 than marginal zone lymphocytes and MBC, which were almost DBA negative. In neoplastic diseases tumour cells in MCL were DBA.44, CD74, and CDw75 positive. MBCL showed a positive reaction for CD74 and CDw75, but positivity for DBA.44 was observed in only one of seven cases. The HCL specimens, all positive for DBA.44, showed a weaker reaction for CD74 and a stronger reaction for CDw75 than either MCL and MBCL specimens. CONCLUSION--These results show that mantle zone lymphocytes and MCL more closely matched HCL for reactivity to DBA.44 than MBC and MBCL. Reactivities for DBA.44 and CDw75 were greater in MBCL compared with its non-neoplastic counterpart, MBC.

The cytological spectrum of the monocytoid B-cell reaction: recognition of its large cell type

To analyse the cytological features of benign monocytoid B-cells, we investigated, histologically and immunohistochemically, 78 reactive lymphadenopathies expressing monocytoid B-cell reactions. Within a broad cytological spectrum of reactive monocytoid B-cells, two cytological types can be recognized: 1 the common type composed of medium-sized cells with irregular or bean-shaped nuclei and inconspicuous nucleoli, and 2 the large cell type composed of cells considered to represent large transformed monocytoid B-cells, with less pleomorphic round nuclei with vesicular chromatin and moderately basophilic, prominent nucleoli. In between these variants transitional forms showing evolution to large transformed monocytoid B-cells occurred. While monocytoid B-cell reactions in 70.5% of all cases were composed predominantly of the common type of monocytoid B-cells, in 29.5% of cases the large transformed cells prevailed. The two distinctive cytological types of reactive monocytoid B-cells seem to have their neoplastic counterparts in monocytoid B-cell lymphoma, including its large cell variant.

Monocytoid B-cell lymphoma with a distinctive clinical presentation

Monocytoid B-cell lymphoma (MBCL) is a recently described non-Hodgkin's lymphoma. Patients with MBCL usually present with localized or generalized lymphadenopathy; peripheral blood and bone marrow involvement is rare. Patients with leukemic manifestations typically have advanced disease with extensive lymph node and bone marrow involvement. We report a distinctively unusual case of MBCL with peripheral blood and splenic involvement at presentation and with no evidence of peripheral lymph node disease. This case emphasizes the fact that malignancies of monocytoid B cells should be viewed as a spectrum of disease that ranges from leukemia to lymphoma. This feature is similar to other low-grade B-cell neoplasms, such as chronic lymphocytic leukemia/small cell lymphoma, lymphocytic type.

Monocytoid B-cell lymphomas: an assessment of diagnostic criteria and a perspective on histogenesis

To determine which morphologic criteria are most useful in distinguishing reactive from malignant monocytoid B cells (MBCs), we compared 16 monoclonal cases (11 nodal, five extranodal) of monocytoid B-cell lymphoma (MBCL) with 12 cases of various reactive diseases in which MBCs were polyclonal. The results of our study showed that in MBCL the MBC component was the predominant architectural finding and that there was confluence of MBCs in all but one case. In contrast, the MBC component did not predominate in the reactive group (P less than .000001) and focal confluence was seen in only one case. A cytologic comparison showed that in MBCL areas there were more large transformed (prominent nucleolated) MBCs (P = .003), a higher mitotic rate (P = .03), and more nuclear irregularities (P = .007) than were present in the reactive group. In addition, evolution to an aggressive histologic type was found in four cases of MBCL. Our results also revealed concomitant multiple, monoclonal, morphologically distinct populations in other compartments (follicular center cells in seven, mantle cells in five, small lymphocytes in five, and plasma cells in 11). These unique findings can be reconciled by postulating (1) that the simultaneous presence of these diverse cytologic types represents morphologic expressions of a B cell whose population is in different phases of its cell cycle and/or its evolution or (2) that the histogenesis of MBCL is possibly from a nodal pluripotent B-stem cell that can differentiate directly into these various cytologic types.

Syndrome of severe skin disease, eosinophilia, and dermatopathic lymphadenopathy in patients with HTLV-II complicating human immunodeficiency virus infection

Two intravenous drug users dually infected with human immunodeficiency virus type 1 (HIV-1) and human T-cell leukemia virus type II (HTLV-II) developed an unusual severe dermatitis characterized by progressive brawny induration, fissuring, and ulceration of the skin, with an associated CD8 cell infiltration in one patient. Both patients had persistent eosinophilia. Lymph node biopsy revealed dermatopathic lymphadenopathy, an unusual pathologic finding in HIV-1 infection but one seen in association with mycosis fungoides and other skin disorders. Two new isolates of HTLV-II virus were established from these patients and were identified as HTLV-II by Southern blotting. This type of skin disease and lymph node pathology has not been found in other intravenous drug users who have been infected with HIV-1 alone or in patients in other risk groups for HIV-1 infection. HTLV-II may play a role in this unique new disease pattern in patients infected with HIV-1.

The histiocytoses of childhood

The histiocytoses of childhood include Langerhans' cell histiocytosis, haemophagocytic syndrome (familial and reactive), sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease), juvenile xanthogranuloma and malignant histiocytosis. These disorders show wide variation in their clinical presentation, prognosis and genetic implications. All are characterized by localized or generalized proliferation of histiocytes, but they differ in their morphology, histochemical and immunochemical staining patterns and electronmicroscopical features. On the basis of a comprehensive clinical history and critical interpretation of morphology and immunocytochemistry using an appropriately selected panel of antibodies, a diagnosis can be reached in the majority of cases.

Monocytoid B-cell lymphoma: morphological variants and relationship to low-grade B-cell lymphoma of the mucosa-associated lymphoid tissue

Twenty-eight cases of monocytoid B-cell lymphoma of lymph nodes and 16 lymph node metastases of primary gastric lymphomas, mostly low-grade B-cell lymphomas of mucosa-associated lymphoid tissue (MALT) type were investigated morphologically and immunohistochemically. Both groups showed the same morphological and immunohistochemical features: diagnostically important sites of infiltration were the sinuses and the marginal zones. The tumour cells were either medium-sized or small. The cytoplasm stained grey with Giemsa and was sometimes rather pale. In imprints the grey colour of the cytoplasm was a characteristic feature. The medium-sized cell type was more frequent; in one third of the cases it was combined with a prominent lymphoplasmacytic component from the same clone, and it resembled the monocytoid B-cells of the sinuses. The small cell type was less common, was not combined with a lymphoplasmacytic component and more closely resembled marginal zone cells. The difference was underlined by the negative reaction with the monoclonal antibody Ki-B3 in the small cell type, which, conversely, was positive in the medium-sized cell type and in the monocytoid B-cell reaction of the sinuses. Both of these cell types, however, showed a granular reaction with the new monoclonal antibody Ki-Mlp. The morphological and immunohistochemical parallels are arguments in favour of the assumption that monocytoid B-cell lymphoma is the nodal equivalent of low-grade B-cell lymphoma of MALT type. This is further supported by the fact that in nine of our 28 cases of monocytoid B-cell lymphoma, lymphomas were found simultaneously or subsequently in organs of the MALT. Monocytoid B-cell lymphoma must be differentiated from an infiltration that occurs in the form of clusters of monocytoid B-cells in other low-grade B-cell lymphomas, especially in immunocytoma with a high content of epithelioid cells.

Monocytoid B-cell lymphoma: a study of 36 cases

We have studied 36 cases of monocytoid B-cell lymphoma (MBCL). We confirm the predilection for females (30 of 36; ratio, five women to one man). The median age was 65 years (range, 29 to 85 years). Monocytoid B-cell lymphoma characteristically involves peripheral lymph nodes (30 of 36) with a propensity for paraparotid or intraparotid nodes. Salivary glands were affected in five patients. Other extranodal sites of involvement included breast, thyroid, stomach, and soft tissue of chest wall. Eight patients manifested with Sjögren's syndrome, one had systemic lupus erythematosus, one presented initially with Raynaud's phenomenon, and two had a monoclonal gammopathy. "Composite lymphomas" were encountered in seven patients. In addition, association with or progression to a higher-grade lymphoma, ie, mixed small and large cell (one) and large cell (six), was observed in seven patients and was associated with a more aggressive behavior of the lymphoma. Immunohistochemical studies performed on biopsy sections from 20 patients confirmed the B-cell nature of MBCL. An average reactivity of less than 10% of the monocytoid B cells with the proliferation marker Ki-67 was demonstrated, in keeping with the indolent behavior of MBCL. Despite our observation of follicular lymphomas frequently accompanying MBCL, the t(14;18) chromosomal translocation does not appear to play a pathogenetic role for MBCL, as determined by molecular studies for the t(14;18) chromosomal translocation and immunologic studies for the BCL2 protein. Our observations also provide support for the proposal that there is an overlap between MBCL and "MALT lymphomas" (those arising from mucosa-associated lymphoid tissue).

Monocytoid B-cell lymphoma in patients with Sjögren's syndrome: a clinicopathologic study of 13 patients

A recent clinicopathologic study of a series of patients with monocytoid B-cell lymphoma (MBCL) indicated that there is a frequent association between MBCL and Sjögren's syndrome (SS) and raised the possibility of a relationship between these two disease entities. To further investigate the possible relationship of MBCL and SS, we studied pathologic and clinical characteristics of 13 patients with MBCL who had clinically documented SS. In all patients, the lymphoma had the characteristic morphologic features of MBCL, and immunologic and molecular hybridization studies confirmed the B-cell nature of the lymphoma. Twelve of the 13 patients were female, with a median age of 66 years at diagnosis. Eleven had localized disease and presented with either salivary gland or cervical lymph node enlargement; one patient presented with a breast mass, and another with generalized lymphadenopathy and hepatosplenomegaly. In five of 13 patients, the MBCL was associated with or progressed to large cell lymphoma. In two patients, there was bilateral involvement of the parotid gland; one had a synchronous high-grade lymphoma in both parotid glands. In two patients, bone marrow biopsies showed involvement by MBCL. Eleven patients are alive 2 to 55 months after the diagnosis of MBCL. One patient died with the disease 8 months after the initial diagnosis. Another patient died of an unrelated cause without evidence of disease 16 months after the diagnosis of MBCL. We conclude that there is a more than fortuitous association between MBCL and SS. This concept is consistent with previously reported observations of reactive monocytoid B cells in patients with benign lymphoepithelial lesions of salivary glands, which may result from selective homing of reactive monocytoid B lymphocytes to the benign lymphoepithelial lesions and their subsequent neoplastic transformation.

Monocytoid B cell lymphoma: clinical and prognostic features of 21 patients

Twenty one patients between 34 and 83 years of age with monocytoid B cell lymphoma (MBCL) of the lymph node were studied. The histological picture characteristically showed broad strands of medium sized cells with irregularly shaped nuclei and a fairly broad rim of slightly basophilic cytoplasm. One case developed into a centroblastic polymorphic lymphoma. Bone marrow infiltration was documented in three cases and leukaemic conversion in one case of MBCL. Seven patients had enlarged spleens. Eight patients were in stage I, five in stage II/IIE, two in stage IIIs and six in stage IV at the time of diagnosis. Of 18 patients subsequently followed up, eight were in complete remission, two in partial remission, and three were undergoing treatment at completion of the study; five patients had died. Relapse occurred in nine patients and was a common feature of MBCL. The prognosis of MBCL was comparable with that of other low grade malignant lymphomas. Fourteen patients presented with primary nodal lymphoma. In seven patients with nodal MBCL, however, a concomitant low grade B cell lymphoma of the mucosa-associated lymphoid tissue (MALT) was also found in the stomach (n = 4), nasopharynx (n = 1), salivary glands (n = 1) and thyroid gland (n = 1). Two of these cases developed into high grade lymphoma. These extra-nodal manifestations were found simultaneously with MBCL in five patients. In another two patients, however, these symptoms occurred in a later phase of the disease. It is emphasised that adequate staging procedures must be carried out in any case of nodal MBCL to exclude underlying low grade B cell lymphoma of the MALT.

Immunophenotypic similarities of mediastinal clear-cell lymphoma and sinusoidal (monocytoid) B cells

Using 14 well-defined (clustered) monoclonal antibodies (MAbs) against B-cell restricted/associated differentiation and activation (CD) antigens and 12 mediastinal clear-cell lymphomas (MCCL), 46 follicular-center-cell lymphomas (FCCL), and 20 non-neoplastic lymph nodes--including toxoplasmic and HIV-associated lymphadenitis--were immunohistochemically examined to determine the histogenesis of MCCL. Antigenically, MCCL was characterized as CD5-, CD10-, CD19+, CD20+, CD21-, CD22+, CD30-, CD37+, CDw40+, and by a frequent expression of CD11c and CD23, while other antigens were inconsistently expressed. The antigenic profiles of MCCL and FCCL showed statistically significant differences in 4/14 distinct antigens. When the neoplastic cells of both tumor groups were compared with morphologically defined normal B-cell types, the overall resemblance of their immunophenotypes was even closer between MCCL and sinusoidal (monocytoid) B cells than between FCCL and follicular-center B cells. We conclude that MCCL is a lymphoma type distinct from FCCL, most probably representing a highly malignant neoplasm corresponding to sinusoidal B-cell reaction.

Hashimoto's thyroiditis lacks detectable clonal immunoglobulin and T cell receptor gene rearrangements

The development of B cell lymphoma, predominantly of the large-cell type, in patients with autoimmune diseases such as Hashimoto's thyroiditis or Sjogren's syndrome is well known. In Sjogren's syndrome, it has been recently shown that the benign-appearing lymphocytic infiltrates of the lymphoepithelial lesions in the salivary glands have clonal rearrangements of immunoglobulin genes in their DNA, even in the absence of malignant lymphoma. To investigate whether a similar situation occurs in Hashimoto's thyroiditis, we studied the thyroid glands from four patients with this disease. In all four cases, there was a benign-appearing lymphocytic infiltrate in the thyroid, with eosinophilic changes in the Hurthle cells. In immunologic studies, we determined that the lymphocytes were polyclonal in each case. We extracted DNA from the frozen tissue blocks of these four patients and analyzed it by molecular hybridization for the presence of clonal immunoglobulin (IgH, kappa, and lambda) and T cell receptor beta chain gene rearrangements, and detected none in any case. Therefore, we conclude that the lymphocytes in Hashimoto's thyroiditis are immunologically and immunogenetically polyclonal proliferations of cells, and that the initial lesion of Hashimoto's thyroiditis does not contain a detectable clone of cells that may eventually develop into malignant lymphoma.

Monocytoid B-cell lymphoma, a tumour related to the marginal zone

Monocytoid B-lymphocytes are a B-cell subset present in subcapsular sinuses in some cases of lymphadenitis. We describe a case of lymphoma of this cell type. The tumour shows a distinctive morphology characterized by concentric strands of tumour cells around lymphoid follicles with hyperplastic germinal centres and conserved mantle zones. Electron microscopy of these cells shows short cellular processes as well as moderate development of endoplasmic reticulum. The phenotype of the tumour was monoclonal IgM-kappa, distinct from other node-based B-cell subpopulations and suggesting a possible relationship to the lymphocytes of the marginal zone present peripheral to lymphoid follicles of the spleen. Morphological features that suggest a relationship with hairy cell leukaemia are contrasted by phenotypic differences and the ultrastructural absence of ribosomic lamellar complexes.

Monocytoid B-cell lymphoma

A case of malignant lymphoma probably representing the neoplastic counterpart of "monocytoid B cells" is described. The lymphoma cells had medium-sized, oval to indented nuclei and moderate amounts of pale cytoplasm. Immunohistochemical studies on cryostat sections revealed positive staining for pan-B, B1, B4, BA2, 12 (HLA-DR), and IgM lambda, but not T-cell or monocytic markers.

Histopathology of bone marrow in human immunodeficiency virus infection

The clinical and haematological findings in 18 patients with human immunodeficiency virus (HIV) infection were correlated with the histological features of plastic embedded bone marrow biopsies. Fifteen patients presented with peripheral cytopaenia of one or several cell lines. Twelve (66%) of the 18 patients exhibited bone marrow findings including normo- to hypercellularity, myelodysplasia, lymphocytosis with or without plasmacytosis and fibrosis of the reticulin type. Seventeen patients had myelodysplastic features, 5 of the 3 haematopoietic lines, 10 of 2 lines and 2 of 1 line. Dysmegakaryocytopoiesis and dyserythropoiesis, seen in 88% and 83% of the 18 patients respectively, were the most common myelodysplastic features. Bone marrow gelatinous transformation (serous atrophy) was a conspicuous finding in 7 (38%) of the 18 patients. The constellation of histological features here described, although not pathognomonic, is highly suggestive of HIV infection. The pathogenesis of the haematological abnormalities in HIV infection is discussed.

Diagnostic specificity of histologic features in lymph node biopsy specimens from patients at risk for the acquired immunodeficiency syndrome

The most common histologic pattern observed in lymph node biopsy specimens from homosexual men with the syndrome of persistent generalized lymphadenopathy is that of florid hyperplasia of germinal centers. This change has been characterized as showing large and irregular germinal centers, mantle zone effacement, follicle lysis, germinal center hemorrhage, granuloma formation, and focal sinusoidal monocytoid cell hyperplasia. Fifty lymph node biopsy specimens coded as nonspecific reactive follicular hyperplasia and antedating the epidemic of the acquired immunodeficiency syndrome (AIDS) (1976 to 1977) were studied to assess the specificity of these features in identifying patients at risk for AIDS. The incidence of these features was as follows: large irregular germinal centers, 10 per cent of the cases; mantle zone effacement, 44 per cent; follicle lysis, 42 per cent; germinal center hemorrhage, 24 per cent; sinus monocytoid cell hyperplasia, 16 per cent; and granuloma formation, 8 per cent. Large irregular germinal centers were seen in five cases, four of which had additional abnormalities. A combination of three germinal center changes was seen in 18 per cent of the cases and a combination of two changes in 16 per cent. Comparison of these data with previously published descriptions of lymph node biopsies from patients with persistent generalized lymphadenopathy indicates that, while some of the reported features may be more common in these patients, none of them, either singly or in combination, can be considered diagnostic of this disorder.