Monocytoid B-cell lymphoma. The biologic and clinical implications of peripheral blood involvement.

Monocytoid B-cell lymphoma (MBCL) is a newly recognized malignant lymphoma that shares clinical and pathologic features with other low-grade B-cell neoplasms, especially small lymphocytic lymphoma and hairy cell leukemia. However, although circulating malignant cells and bone marrow involvement are relatively common in small lymphocytic lymphoma and are characteristic features of hairy cell leukemia, MBCL in the peripheral blood and bone marrow rarely have been described. From 124 patients entered in the MBCL registry, three cases with peripheral blood involvement are described and the clinical and pathologic features in these patients are compared with those of other low-grade B-cell neoplasms. Monocytoid B-cell lymphoma was confirmed by lymph node biopsy in each case. Two patients had lymphocytosis at the time of presentation; the remaining patient presented with pancytopenia. For each patient, phenotypic studies of lymph node and peripheral blood revealed identical monoclonal surface immunoglobulin expression. The morphologic appearance of the circulating MBCL cells was different in each case, varying from a relatively homogeneous population of small lymphocytes to a heterogeneous collection of large and small lymphoid cells. The two patients with lymphocytosis also had extensive replacement of the bone marrow by MBCL; the third patient had diffuse infiltration by MBCL in a normocellular marrow. All three patients had advanced-stage (Stages III or IV) disease, and all required systemic chemotherapy for disease control. The two patients with lymphocytosis had relentless, progressive infirmity despite relatively aggressive treatment regimens. These patients ultimately died of lymphoma 13 and 18 months after initial diagnosis. The third patient is alive and well with stable disease 30 months after coming to the authors' institution. The clinical and pathologic features of the patients reported here reaffirms the placement of MBCL in the spectrum of low-grade B-cell neoplasms. However, unlike small lymphocytic lymphoma and hairy cell leukemia, MBCL only rarely undergoes leukemic conversion. Furthermore, it appears that peripheralization of MBCL occurs primarily in patients with advanced-stage disease and may be indicative of a relentless course and progressive disease despite aggressive chemotherapeutic intervention.     

Comparison of immunophenotypes of small B-cell neoplasms in primary lymph node and concurrent blood or marrow samples

Immunophenotyping of small B-cell neoplasms (SBCNs) may have a critical role in diagnosis. However, there are few data addressing whether the immunophenotypes of SBCNs in bone marrow (BM) and peripheral blood (PB) are representative of those in other tissue sites. We compared the immunophenotypic features of concurrently analyzed lymph node (LN) and BM/PB specimens using multiparameter flow cytometry. Fifty-five SBCNs were identified: 27 follicular lymphomas (FLs), 16 chronic lymphocytic leukemia/small lymphocytic lymphomas (CLL/SLLs), and 12 mantle cell lymphomas (MCLs). Major (presence vs absence) or minor (alteration of intensity) variations in expression of individual antigens between LN and BM/PB were observed in up to 25% of cases within a particular SBCN category. All FLs and CLL/SLLs maintained characteristic immunophenotypes in BM/PB. Potentially misleading variations included 1 case of MCL that failed to express CD5 in BM and likely would have been immunophenotypically misclassified as a marginal zone lymphoma and another MCL that expressed moderate CD23 in PB and would have required additional studies for precise classification. The remaining major and minor variations would not have affected interpretation.     

An unusual B-cell lymphoma simulating hairy cell leukemia

The authors report an unusual B-cell lymphoma that simulated hairy cell leukemia (HCL) not only clinically but also pathologically in peripheral blood, bone marrow, and lymph node specimens. A diagnosis of lymphoma could be made only after pathologic examination of the spleen, indicating that caution should be exercised in making a primary diagnosis of HCL on bone marrow examination. Morphologically this lymphoma resembled monocytoid B-cell lymphoma (MBCL) but the immunophenotype (monoclonal Ig-kappa +, Ia+, B4+, Leu-1+, LN-2+, lambda-, Bl-, LN-1- and CALLA-) and clinical findings were more consistent with mantle zone lymphoma (MZL). Because this case demonstrates features of both MBCL and MZL, the authors suggest that these two entities may have a common histogenesis.     

Mantle cell lymphoma concurrent with T-large granular lymphocytic leukemia: report of a case and review of literature

Mantle cell lymphoma is one of the B-cell lymphomas. The concurrent presentation of mantle cell lymphoma with large granular lymphocytic leukemia simultaneously has never been reported. In this case we present an old man with concomitant mantle cell lymphoma and large granular lymphocytic leukemia diagnosed by the morphology of the bone marrow aspiration, immunophenotyping of the peripheral blood by flow cytometry detecting the increased CD3+CD4-CD8+ cells, immunohistochemical studies of lymph node showed cyclinD1+, chromosome analysis by fluorescence in situ hybridization (FISH) showed t(11,14), positive results of IGH and TCR rearrangement studies. The patient discharged from the hospital voluntarily and lost the follow-up. A brief discussion is also presented.     

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 Sj?gren'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: 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.     

Primary splenic diffuse large B-cell lymphoma manifesting in red pulp

We evaluated six cases of diffuse large B-cell lymphoma (DLBCL) involving the red pulp of the spleen. All had B symptoms and an aggressive clinical course. The lymphoma cells proliferated diffusely and non-cohesively in the cords of the red pulp. The lymphoma involved the bone marrow in four of the five patients and the liver in all four of the patients examined. However, lymph node (LN) involvement was rare at presentation, and systemic LN involvement was not observed even in the terminal phase. The lymphoma cells infiltrated the intrasinusoidal/intravascular and interstitial spaces of the involved tissues and were detected in the peripheral blood in two of the six patients. CD5-expressing lymphoma cells were detected in four of the five patients examined. Because these cases had some unique clinical features and occurred in distinct splenic sites, we proposed that primary splenic DLBCL manifesting in red pulp is a distinct clinicopathological entity.     

bcl-2 expression by multicolor flow cytometric analysis assists in the diagnosis of follicular lymphoma in lymph node and bone marrow

The expression of bcl-2, CD10, and CD20 was examined by multicolor flow cytometry in 78 samples including lymph node or other tissue biopsy specimens containing follicular lymphoma (FL; n = 17), reactive hyperplasia (RH; n = 28), or other malignant lymphomas (n = 20), as well as bone marrow aspirates (n = 13). The presence of CD10+ cells with high bcl-2 expression predicted the presence of FL rather than RH with a positive predictive value of 100% and negative predictive value of 96%. CD10+ cells with high bcl-2 expression also were found in a subset of diffuse large B-cell lymphomas and were otherwise rare in other types of malignant lymphoma. In contrast with immunohistochemical studies, a reduced but apparently measurable level of bcl-2 was present in benign follicular center cells. Hematogones showed lower bcl-2 levels than did FL cells in the bone marrow, and neutrophils were bcl-2-. Measurement of bcl-2 expression levels by multiparameter flow cytometry offers a rapid, quantitative assessment that may assist in the diagnosis of FL in lymph nodes or bone marrow, even when other CD10+ cells or admixed normal B cells are present.     

Antigenic phenotypes of hairy cell leukemia and monocytoid B-cell lymphoma: an immunohistochemical evaluation of 66 cases.

Using a large panel of antibodies on multi-tumor block sections of routinely processed, paraffin-embedded fixed tissue, we compared the antigenic phenotype of 42 clinically, morphologically, and immunologically well-characterized cases of hairy cell leukemia (HCL) with 24 cases of monocytoid B-cell lymphoma (MBCL) selected from the Monocytoid B-Cell Lymphoma Registry at the City of Hope National Medical Center. The predominant antigenic phenotype of hairy cells was CD45 (leukocyte common antigen)+, CD45Ra (4KB5, MB1, MT2)+, L26+, CDw75 (LN1)+, CD74 (LN2)+, LN3+, MB2+, CD45RO (UCHL1)-, MT1-, CD15 (Leu-M1)-, neuron-specific enolase (NSE)-, epithelial membrane antigen-, and CD30 (Ber-H2)-. The immunophenotype of neoplastic monocytoid B lymphocytes was essentially identical to that of the hairy cells, with one exception: the neoplastic monocytoid B lymphocytes were stained by epithelial membrane antigen in seven cases. An interesting observation was the staining by anti-muscle-specific actin of the neoplastic cells of MBCL in 53% of cases, but of none of the cases of HCL. The results of our study (1) indicate that HCL and MBCL can be immunophenotyped reliably on fixed tissue samples, (2) further confirm the proposed lineage relationship between these two lymphoproliferative disorders, and (3) indicate that decalcification of bone marrow biopsies does not adversely affect the immunoreactivity of hematopoietic-associated antigens.     

Aberrant expression of T-cell-associated antigens on B-cell non-Hodgkin lymphomas

We describe 9 well-characterized cases of B-cell non-Hodgkin lymphoma (NHL) that showed aberrant expression of T-cell-associated antigens by 2-color flow cytometry. Cases were as follows: chronic lymphocytic leukemia/small lymphocytic lymphoma, 4; follicle center cell lymphoma, 2; mantle cell lymphoma, 1; and diffuse large B-cell lymphoma, 2. CD2 was the most commonly expressed antigen (5 cases). CD8 and CD7 were identified in 2 cases each, including 1 case that expressed both CD7 and CD4. The disease course and response to treatment were compatible with the type and stage of lymphoma. No unusually aggressive behavior was noted in any case. A control group of 59 cases of benign lymph nodes analyzed during the same period showed no aberrant expression of T-cell-associated antigens; thus, such expression is not a feature of benign lymphoid proliferations. Study of these B-cell lymphomas may prove invaluable to study aberrant activation of silent or repressed T-cell differentiation genes. CD2-expressing B-cell NHLs may represent clonal expansion of CD2+ B lymphocytes that normally constitute a small fraction of peripheral B lymphocytes and should not be confused with composite B- and T-cell lymphomas. Unless aggressive behavior is noted consistently, no aggressive treatment is justified.     

Lymphoplasmacytic lymphoma/Waldenstr?m macroglobulinemia associated with Hodgkin disease. A report of two cases.

Although the clinical course of lymphoplasmacytic lymphoma (LPL)/Waldenstr?m macroglobulinemia (WM) is usually indolent, high-grade non-Hodgkin lymphoma may develop in a small subset of patients. We have not found any patients with LPL/WM associated with Hodgkin disease (HD) described in the literature, prompting us to report 2 cases. In case 1, the patient had LPL/WM involving bone marrow diagnosed 1 week before left supraclavicular lymph node biopsy revealed LPL/WM and classical HD. In case 2, the patient had a 15-year history of LPL/WM before classical HD developed involving bone marrow, liver, and lymph node. Both cases were positive for IgM, monotypic immunoglobulin light chain, and B-cell antigens and were CD3-. The neoplastic Hodgkin cells were CD15+, CD20+ (case 1), CD30+, CD3-, and CD45- and were negative for Epstein-Barr virus RNA. Both patients were treated with chemotherapy for HD. In case 1, clinical response was excellent with no histologic evidence of HD in subsequent biopsy specimens. In case 2, HD was progressive at last follow-up, despite therapy. Patients with LPL/WM, similar to patients with other types of low-grade B-cell lymphoma, can develop HD that may respond to chemotherapy.     

Immunohistological characterization of malignant lymphomas of the Waldeyer''s ring other than the nasopharynx

Among extranodal lymphomas, the Waldeyer's ring is the second most frequently involved site after the gastrointestinal tract. Fresh tissue from 23 consecutive cases of malignant lymphoma of the faucial tonsil, palate and base of tongue were studied histologically and with a panel of 25 monoclonal antibodies. Twenty cases were primary Waldeyer's ring lymphoma, and all were found to express B-cell phenotype. Most cases were classified as diffuse centroblastic lymphoma, polymorphic subtype, in which there were immunoblast-like, centrocyte-like and/or multilobated centroblasts. All except one case expressed all three B-cell lineage antigens CD19, CD20 and CD22, but they showed inconsistent expression of the B-cell antigens CD9 and CD24. Four cases lacked surface immunoglobulin. Six cases expressed interleukin-2 receptor, suggesting that they were composed of highly activated B-cells. Three cases represented relapse in the tonsil or tongue in patients with known malignant lymphoma in other sites; one case expressed T-cell and two cases B-cell phenotype (both of which also expressed interleukin-2 receptor). The clinical features and immunohistological findings suggest that Waldeyer's ring lymphomas, other than those of the nasopharynx, share some of the characteristics of 'mucosa-associated lymphoid tissue' lymphomas. In contrast, nasopharyngeal lymphomas are more related to nasal lymphomas, and are almost exclusively peripheral T-cell neoplasms.     

Follicular lymphoma of compartmentalized small cleaved center cells and mantle zone lymphocytes. Evidence for a common derivation.

The authors have observed a unique case of follicular lymphoma in which the central zones of neoplastic nodules were composed predominantly of small cleaved cells (SCC) that were surrounded by small lymphoid cells proliferating in wide mantles as in mantle zone (MZ) lymphoma. The central SCC component displayed a follicular SCC lymphoma-like phenotype (IgD-, CD10+, CD5-, CD68-), whereas the neoplastic cells of the peripheral zones had an MZ lymphoma-like phenotypic profile (IgD+, CD10-, CD5+, CD68+). In extranodal involved tissues, either follicular or diffuse (leukemic-like) patterns of lymphoma infiltration were noted. Flow cytometric analyses showed in the bone marrow or the peripheral blood two leukemic B cell populations, one mimicking the phenotypic profile (IgM+, IgD+, CD5+, CD10-, Leu8-) of small lymphoid cells with MZ-like features, and the other with phenotypic features (IgM+, IgD-, CD5+, CD10+, Leu8+) intermediate between those of MZ-like cells and those of the SCC component (follicular center-like) detected in the lymph node. Immunomagnetic sorting and gene rearrangement studies indicated that both CD10+ and CD10- B lymphocytes and lymph node neoplastic B cells shared the same clonal origin. This unusual follicular lymphoma can be viewed as the result of the proliferation of a single follicular progenitor capable of differentiating toward both a germinal center and an MZ phenotype. The simultaneous presence in the same patient of at least three neoplastic B-cell populations at different maturation stages, encompassing follicular center and MZ phenotypes, and showing the same clonal derivation, indicates a close lineage relationship between follicular SCC and MZ lymphomas.     

Stereotactic biopsy diagnosis of primary non-Hodgkin's lymphoma of the central nervous system. A histological and immunohistochemical study

We report 29 cases of primary non-Hodgkin lymphomas (NHL) of the Central Nervous System (CNS), 26 of which were diagnosed by stereotactic biopsy and 3 by autopsy. In seven cases the patients were affected by AIDS. Histological examination of this series revealed 15 cases of immunoblastic lymphoma, 12 cases of centroblastic lymphoma, 1 case of lymphoplasmacytic immunocytoma and 1 case of unclassified high grade lymphoma. By immunohistochemistry the B-cell origin of lymphoma cells was demonstrated in 28/29 cases. Eight cases were assigned to the B-cell lineage by demonstration of monotypic surface or cytoplasmic immunoglobulin or of the B-cell phenotype CD22+, CD2-, CD3-, CD5-. In twenty cases the B-cell nature of lymphoma was identified by positivity with two or more anti-B monoclonal antibodies (LN1LN2MB2) and negativity by the anti-T monoclonal antibody UCHL1. The histologically unclassified case was a peripheral T-NHL (CD1-, CD2+, CD3-, CD5+, CD22-). We conclude that histological and immunohistological evaluation of stereotactic biopsy specimens provides sufficient information for diagnosis and phenotypic characterization of primary NHL of the CNS. These lymphomas exhibit important predominance of high-grade malignancy histological types and are nearly always B-cell derived. In addition, we provide further evidence that the panel of monoclonal antibodies LN1, LN2, MB2, and UCHL1 is useful for immunophenotypic characterization of brain lymphomas when only paraffin embedded stereotactic biopsy tissue is available.     

Monocytoid B-cell lymphoma in patients with Sj?gren'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 Sj?gren'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.     

Systemic Tropheryma whippleii infection associated with monoclonal B-cell proliferation: a Helicobacter pylori-type pathogenesis?

We report a case of Whipple disease in a 55-year-old woman who presented with arthralgia, weight loss, and lymphadenopathy. Tropheryma whippleii bacilli were identified in the mesenteric lymph nodes by diastase-resistant periodic acid-Schiff stain and confirmed by electron microscopy. Retrospectively, previous biopsy specimens from the duodenum and right axillary lymph node of this patient, which were initially considered to demonstrate reactive changes, also showed features consistent with involvement by Whipple disease. At the time of presentation, a large kappa-restricted monoclonal B-cell population with the phenotype CD20+CD19+CD5-CD10- was identified in the patient's peripheral blood, lymph nodes, and bone marrow by flow cytometry study. The monoclonality of the mesenteric lymph node B cells was confirmed by immunohistochemical stain for kappa chain after antigen retrieval and also by polymerase chain reaction with the primer set targeting FR2-V(H). Routine cytogenetic study failed to reveal any chromosomal abnormalities, and polymerase chain reaction for Bcl-2 major and minor breakpoint cluster of t(14:18) was not detected. The monoclonal B cells have persisted in blood for the entire follow-up period (10 months). The possibility of reactive monoclonal B-cell proliferation versus Whipple disease-related B-cell lymphoma is discussed.     

A common clonal origin of nodal marginal zone B-cell lymphoma and plasma cell myeloma demonstrating different immunophenotypes: a case report of composite lymphoma.

We demonstrated an 83-year-old male case of composite lymphoma. Before 18 years, he was diagnosed with nodal marginal zone B-cell lymphoma in the cervical lymph node. Peripheral blood showed anemia and IgA (kappa)-type monoclonal gammopathy (IgA; 3,625 mg/dL). Bone marrow aspiration biopsy exhibited plasma cell myeloma, in which atypical plasma cells were positive for cytoplasmic IgA (kappa) and atypical lymphoid cells intermingled were positive for CD20. In contrast, cervical lymph node biopsy revealed nodal marginal zone B-cell lymphoma, in which lymphoma cells were positive for cytoplasmic IgG (lambda). Southern blotting analysis of the IgH gene showed same clonal rearrangement band in both lymph node and bone marrow samples and additional band in the bone marrow. Sequence analyses of the IgH gene showed an identical sequence of CDR3 in both samples. Thus, we demonstrated a common clonal origin of composite lymphoma comprising nodal marginal zone B-cell lymphoma and plasma cell myeloma. Nodal marginal zone B-cell lymphoma recurred in cervical lymph node and involved into the bone marrow, differentiating into plasma cell myeloma in which Ig isotype switched and monoclonal gammopathy developed. Sequence analysis of the IgH gene was a powerful tool for determination of clonal origin.     

HLA-DR expression in B-cell non-Hodgkin's malignant lymphomas: a multiparameter flow cytometry study

Ten cases of reactive follicular hyperplasia and 31 cases of B-cell non-Hodgkin's malignant lymphoma were studied using multiparameter flow cytometry. A bimodal distribution for HLA-DR expression, but not for surface immunoglobulin or B cell-specific antigens CD19 and CD20, was observed commonly in mixed cell type and infrequently in non-mixed cell type B-cell malignant lymphomas. On the basis of HLA-DR distribution alone, 31 cases of B-cell malignant lymphomas of low, intermediate, and high grades could be separated into mixed and non-mixed cell types, with only two misclassifications (P = 0.0001). Exceptionally, one case of malignant lymphoma, follicular and diffuse, mixed-cell type had a unimodal HLA-DR distribution, and one case of malignant lymphoma, diffuse, large noncleaved cell type had a bimodal HLA-DR distribution. In all cases of malignant lymphoma, follicular, mixed-cell type studied, low HLA-DR was correlated with small cells, and high HLA-DR was correlated with large cells. In contrast, HLA-DR expression and cell size were not as directly correlated in cases of malignant lymphoma, diffuse, mixed-cell type. These observations suggest that most, but not all, cases of B-cell malignant lymphomas of the mixed cell type can be separated from other B-cell lymphomas on the basis of HLA-DR distribution.     

Expression of lymphocyte homing receptors and vascular addressins in low-grade gastric B-cell lymphomas of mucosa-associated lymphoid tissue.

In this study, we examined lymphocyte homing receptor and vascular addressin expression in a case of primary gastric B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) with a secondary intestinal spread. We compared the findings with that observed in B cells of normal MALT and MALT acquired as a consequence of Helicobacter pylori-associated gastritis and other low-grade gastric B-cell MALT lymphomas. The neoplastic B cells in the gastric tumor were alpha 4 beta 7-, CD62L+, whereas the intestinal secondary was alpha 4 beta 7+, CD62L-. Incubation of isolated tumor cells from the stomach by H. pylori generated T-cell-dependent proliferation of neoplastic B cells and induced expression of alpha 4 beta 7 integrin similar to the intestinal tumor. These observations indicate that reversal of homing receptor profile in the gastric tumor by antigen specific stimulation may be responsible for secondary intestinal dissemination. In normal stomach and normal MALT, alpha 4 beta 7 and CD62L expression reflected the differentiation of the B cell. Plasma cells were alpha 4 beta 7+, CD62L-, whereas a subset of memory B cells were alpha 4 beta 7-, CD62L+. Homing receptor expression in MALT lymphoma B cells was heterogeneous, however, in line with their memory B-cell phenotype in the majority of cases, the neoplastic B cells were alpha 4 beta 7-, CD62L+. Neoplastic plasma cells were always alpha 4 beta 7+, CD62L-. The venules in normal gastric mucosa expressed mucosal addressin cell adhesion molecule-1 but not peripheral lymph node addressin. In normal MALT, H. pylori-associated follicular gastritis and MALT lymphomas high endothelial venules coexpressed mucosal addressin cell adhesion molecule-1 and peripheral lymph node addressin. These findings suggest expression of lymphocyte homing receptors by B cells and vascular addressins by mucosal venules are similar in normal MALT and MALT lymphomas, and factors controlling normal mucosal B-cell traffic are also operational in MALT lymphomas.