Features Of Mucosa-associated Lymphoid Tissue Research Articles

Serum Immunoglobulin Paraprotein Associated with Inferior Progression Free Survival in Patients with Mucosa-Associated Lymphoid Tissue Lymphoma

IntroductionIn order to investigate the clinical and certain laboratory features of mucosa-associated lymphoid tissue (MALT) lymphoma patients with immunoglobulin (Ig) paraproteinemia and identify the potential prognostic value of Ig paraproteinemia in MALT lymphoma.Methodswe reviewed the medical records of all patients diagnosed with MALT lymphoma and performed Ig paraprotein test at the First Affiliated Hospital of Nanjing Medical University, Jiangsu Province Hospital from April 2010 to December 2016. A total of 115 patients were diagnosed with MALT lymphoma, of which 78 patients had been tested for serum Ig paraprotein. The correlations between serum Ig paraprotein and other prognostic factors were analyzed. Univariate and cox regression analyses were used to assess associations between survival time and potential risk factors.ResultsAmong 78 MALT lymphoma cases, 16 (20.5%) had Ig paraproteinemia, mostly IgM-K (5, 31.3%), followed by IgM-L, IgG-L, IgM-K/IgA-K, IgA-L, IgM-L/IgA-L. According to the correlation analysis, male (P=0.022), advanced Ann Arbor stage (P <0.001), lymph nodes involvement (P <0.001), high level of serum β2-microglobulin (P <0.001) and low level of serum albumin (P= 0.001) were significantly related to the presence of Ig paraproteinemia. Survival analysis illustrated that patients with IgM paraproteinemia had significantly shorter progression-free survival (PFS) (P=0.005) than those without IgM paraproteinemia (Figure 1). Cox regression analysis showed that IgM paraproteinemia was an independent prognostic factor for PFS of MALT lymphoma patients (P=0.037). Risk stratification based on IPI together with IgM paraproteinemia could divide patients with MALT lymphoma into four groups and better identify high or low risk of PFS (P <0.0001) and OS (P <0.0001) in MALT lymphoma patients (Figure 2).ConclusionMALT lymphoma patients with Ig paraproteinemia represent a subgroup with inferior PFS. Serum Ig paraprotein might be applied for the assessment of prognosis in patients with MALT lymphoma. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Morphofunctional features of mucosa-associated lymphoid tissue of intestine as an organ of immune system and its role in the development of diseases

Reticuloendothelial system (RES) is considered one of the local immune response regulation centers. It takes part in most physiological and pathological processes, namely, in local homeostasis, in regulation of trophism and immunological responses of both primary and secondary immune responses. The main cell population of (RES) is a macrophage, which is a stationary cell that can move only within the tissue layer. Dendritic cells as representatives of (RES) as well are under direct control of macrophages. Up to 80% of all immunocompetent cells are concentrated in the intestinal mucosa. For adequate interaction with the intestinal microbiota and ensuring immunological tolerance to normal commensals, there is a lymphoid tissue associated with the intestinal mucosa (gut-associated lymphoid tissue – GALT), in which mononuclear phagocytes perform their most significant functions. When pathogenic microorganisms enter the mucosa, the network of resident macrophages as an immune barrier triggers an inflammatory response to further stabilize homeostasis. However, a pronounced microbial and antigenic load in the gut requires the mandatory presence of specific immune cells – lymphocytes, whose immature forms are located in GALT structures and specialize under the guidance of mononuclear phagocytes. After the final differentiation, lymphocytes expressing integrin α4β7 are able to return from the systemic bloodstream to the intestinal mucosa to perform highly specific functions. This phenomenon is called the homing effect. It was noted that in non-specific ulcerative colitis and Crohn's disease, both the number of regulatory T-lymphocytes and their expression of integrin α4β7 increases. The pathology of the homing effect, according to some researchers, explains the possibility of follow-up secondary lesions in chronic inflammatory bowel diseases with the development of systemic pathology.

PTEN Loss and Cyclin A2 Upregulation Define a PI3K/AKT Pathway Activation in Helicobacter pylori-induced MALT and DLBCL Gastric Lymphoma With Features of MALT.

Helicobacter pylori infection is strongly associated with primary gastric diseases, such as extranodal mucosa-associated lymphoid tissue (MALT) lymphoma, diffuse large B-cell lymphoma (DLBCL) with histologic evidence of MALT origin, and gastric carcinoma. The cytotoxin-associated gene A (CagA) protein behaves as a bacterial oncoprotein, promoting tumorigenesis via dysregulation of the phosphatidylinositol 3-kinase/AKT pathway (PI3K/AKT). We investigated the molecular mechanisms of PI3K/AKT pathway dysregulation in H. pylori-induced MALT and DLBCL gastric lymphoma. Immunohistochemical assays for CagA, phospho(p)-S473-AKT, PTEN, SHIP, and cyclin A2 proteins were performed on samples from 23 patients with H. pylori-positive MALT lymphoma and 16 patients with H. pylori-positive gastric DLBCL. We showed that CagA localization is correlated with the activation of the AKT pathway in both MALT and DLBCL lymphoma cells. Interestingly, we found a close association between the loss of PTEN, the overexpression of cyclin A2, and the phosphorylation of AKT in gastric MALT and DLBCL tumor cells.

Gastric Diffuse Large B-cell Lymphoma Cured with Helicobacter pylori Eradication Regardless of Whether it Contains Features of MALT Lymphoma

A 66-year-old patient was diagnosed with primary gastric B-cell lymphoma. The pathological findings were consistent with diffuse large B-cell lymphoma (DLBCL); however, a small area showed features of mucosa-associated lymphoid tissue (MALT) lymphoma. Biopsy specimens were referred to two other pathologists, both of whom diagnosed the case as pure DLBCL, denying the area of MALT lymphoma. As the lymphoma was limited to the submucosal layer and the patient's general condition was excellent, eradication of Helicobacter pylori was selected as the initial treatment. The lymphoma completely disappeared three months after the eradication treatment, and complete remission has been maintained for nearly two years.

O1-041 - Front-Line Antibiotic Therapy in Early-Stage H. Pylori-Positive Gastric Diffuse Large B-Cell Lymphomas with or Without Malt Features

ABSTRACT Background Our earlier study showed that certain proportion of early-stage H. pylori (HP)-positive gastric diffuse large B-cell lymphoma (DLBCL) with features of mucosa-associated lymphoid tissue (MALT), DLBCL(MALT), could achieve long-term complete pathological remission (pCR) after frontline HP eradication therapy (HPE). In this retrospective, explorative study, we evaluate the efficacy of HPE on early-stage gastric DLBCL without features of MALT, the pure (de novo) DLBCL, in comparison with its efficacy on high-grade transformed gastric MALT lymphoma, the DLBCL(MALT). Methods A total of 50 patients of stage IE/IIE1, HP-positive gastric DLBCL with frontline HPE treatment were included. Of them, 16 patients with pure (de novo) DLBCL were retrospectively identified from medical/pathologic review and 34 patients with DLBCL (MALT) were an expanded cohort of one previously reported multicenter prospective study. pCR was defined as regression of DLBCL to Wotherspoon grade 2 or less in all histologic sections of follow-up endoscopic biopsies. Results HP infection was successfully eradicated in 100% (16/16) of the pure (de novo) DLBCL and 94.1% (32/34) of the DLBCL(MALT) patients. A total of 68.8% (11/16) of pure (de novo) DLBCL and 56.3% (18/32) of DLBCL(MALT) patients achieved pCR after HPE. The median time-to-pCR was 2.1 months (95% CI, 0.6–3.7) for pure (de novo) DLBCL and 5.0 months (95% CI, 2.8–7.5) for DLBCL(MALT) (P = 0.024). At a median follow-up of 7.7 years (95% CI, 4.5–10.9), all patients with pCR after HPE were alive and free of lymphoma, except one patient with pure (de novo) DLBCL died of lung cancer. Conclusions Similar to DLBCL(MALT), a substantial portion of early-stage, HP-positive gastric pure (de novo) DLBCL remains HP-dependent and responds to antibiotic treatment. Prospective studies to validate the findings are warranted.

Helicobacter pylori eradication therapy is effective in the treatment of early-stage H pylori–positive gastric diffuse large B-cell lymphomas

AbstractAn explorative study evaluates the efficacy of Helicobacter pylori (HP) eradication (HPE) therapy on early-stage gastric diffuse large B-cell lymphomas (DLBCLs) without features of mucosa-associated lymphoid tissue (MALT), the pure (de novo) DLBCLs, in comparison with its efficacy on high-grade transformed gastric MALT lymphomas, the DLBCL(MALT). In total, 50 patients of stage IE/IIE1 HP-positive gastric DLBCLs with frontline HPE treatment were included. HP infection was successfully eradicated in 100% (16/16) of the pure (de novo) DLBCL patients and 94.1% (32/34) of the DLBCL(MALT) patients. In total, 68.8% (11/16) of pure (de novo) DLBCL patients and 56.3% (18/32) of DLBCL(MALT) patients achieved complete pathologic remission (pCR) after HPE therapy. The median time to pCR was 2.1 months (95% confidence interval, 0.6%-3.7%) for pure (de novo) DLBCLs and 5.0 months (95% confidence interval, 2.8%-7.5%; P = .024) for DLBCL(MALT). At a median follow-up of 7.7 years, all patients with pCR after HPE therapy were alive and free of lymphomas, except for one patient with pure (de novo) DLBCL who died of lung cancer. Similar to DLBCL(MALT), a substantial portion of early-stage HP-positive gastric pure (de novo) DLBCLs remains HP-dependent and responds to antibiotic treatment. Prospective studies to validate the findings are warranted.

Anatomie und Physiologie der ableitenden Tränenwege

The human nasolacrimal ducts consist of the upper and lower lacrimal canaliculi, the lacrimal sac and the nasolacrimal duct and drain tear fluid from the ocular surface into the nose. The lining epithelium of the lacrimal sac and the nasolacrimal duct is lined by microvilli supporting the hypothesis that tear fluid components are absorbed. Based on its composition epithelial secretions fulfill functions in tear transport and antimicrobial defense. Further defense mechanisms are displayed by IgA and defense cells which show a special intraepithelial and subepithelial distribution. Moreover, tear duct-associated lymphoid tissue (TALT) is present, displaying the cytomorphological and immunophenotypic features of mucosa-associated lymphoid tissue (MALT). The mechanisms of tear outflow are not yet resolved and several hypotheses exist. Significance is attributed to the lacrimal part of the orbicularis eye muscle surrounding the canaliculi, the helically arranged system of connective tissue fibres and the cavernous body that surrounds the lacrimal sac and the nasolacrimal duct. Moreover, the cavernous body has a function in protecting the lacrimal passage and is active during emotions.

MALT lymphoma of the paranasal sinuses and the hard palate: report of two cases and review of the literature

Extra-nodal low-grade B-cell lymphomas arising in the gastrointestinal tract recapitulate the structure and features of mucosa-associated lymphoid tissue, called "MALT lymphomas." In the head and neck region except for the salivary glands the occurrence of this neoplasm is very rare. The authors report on two such cases of MALT lymphoma, one of the hard palate in a 71-year-old woman and the other of the paranasal sinuses in a 69-year-old woman with the history of chronic sinusitis. Such chronic inflammatory conditions can induce the development of MALT lymphoma. Clinical elaboration should include computerized tomography (CT) and magnetic resonance imaging (MRI) for the assessment of tumor extension, bone destruction, lymph node involvement and differentiation of mucosal thickening from tumor mass. Biopsy for histopathological diagnosis is mandatory. Treatment should be surgery, irradiation or combined radio-chemotherapy depending on the stage of the disease.

Long-Term Results of Anti– Helicobacter pylori Therapy in Early-Stage Gastric High-Grade Transformed MALT Lymphoma

Several independent clinical studies have reported that Helicobacter pylori eradication therapy could achieve complete remission in some patients with H. pylori-positive early-stage gastric mucosa-associated lymphoid tissue (MALT) lymphoma. To compare the long-term results of anti-H. pylori therapy in early-stage, gastric low-grade and high-grade transformed MALT lymphoma, two multicenter prospective studies of anti-H. pylori therapy for early-stage gastric lymphoma conducted in Taiwan, one for low-grade MALT lymphoma, with 34 patients enrolled from March 1996 through April 1999, and one for high-grade transformed tumors (diffuse large B-cell lymphoma with features of MALT, DLBCL[MALT] lymphoma), with 24 patients enrolled since June 1995, were directly compared. In both studies, patients generally received 2 weeks of antibiotics and had multiple sequential follow-up endoscopic examinations until complete histologic remission (CR) or disease progression; patients were monitored through January 31, 2004. CR was defined as regression of lymphoid infiltration to Wotherspoon's score of 2 or less on all pathologic sections of endoscopic biopsy specimens. All statistical tests were two-sided. The H. pylori-positive rate among the 34 low-grade patients was 94% (32 of 34). All 24 selected high-grade patients were H. pylori positive. H. pylori was eradicated in 97% (30 of 31) of evaluable H. pylori-positive low-grade patients and in 92% (22 of 24) of high-grade patients, which led to CR in 80% (24 of 30, 95% confidence interval [CI] = 65% to 95%) and 64% (14 of 22, 95% CI = 42% to 86%) of patients, respectively. None of the five patients who were either initially H. pylori negative or had persistent H. pylori infection after antibiotics achieved CR. After median follow-up of more than 5 years in complete responders, tumor recurrence was observed in three (13%) low-grade patients but not in high-grade patients. Anti-H. pylori therapy may be considered as one of the treatment options for early-stage H. pylori-positive gastric DLBCL(MALT), and large-scale prospective studies to validate its use as first-line therapy for such tumors should be undertaken.

Drainage of Tears: Impact on the Ocular Surface and Lacrimal System

The human efferent tear ducts are part of the lacrimal system. Because little knowledge exists concerning the physiology of the nasolacrimal system, and hence its pathophysiology, the nasolacrimal system has received almost no consideration as a possible factor in dry eye. The human nasolacrimal ducts consist of the upper and the lower lacrimal canaliculus, the lacrimal sac, and the nasolacrimal duct. As a draining and secretory system, the efferent tear ducts play a role in tear transport and nonspecific immune defense. Moreover, components of tear fluid are absorbed in the nasolacrimal passage and are transported into a surrounding vascular system. This system is similar to a cavernous body that is subject to autonomic control and regulates tear outflow. Tear duct-associated lymphoid tissue (TALT) is present in the efferent tear ducts, displaying the cytomorphological and immunophenotypic features of mucosa-associated lymphoid tissue (MALT). Under normal conditions, tear fluid components are constantly absorbed into the blood vessels of the surrounding cavernous body. These vessels are connected to the blood vessels of the outer eye and could act as a feedback signal for tear fluid production, which ceases if these tear components are not absorbed. In this way, dry eye could be initiated. Defective stimulation of TALT could result in abnormal immune deviation at the ocular surface, leading to an autoimmunological response that causes dry eye pathology.

Treatment and survival of 38 female breast lymphomas: a population-based study with clinical and pathological reviews.

Breast lymphomas are rare and consensus about their treatment is lacking. A population-based study of 38 breast lymphomas, registered in the databases of two Comprehensive Dutch Cancer Centers from 1981 to 1999, was performed. The median age of all female patients was 65 years (20-92): 25 patients had localized and 13 patients had disseminated lymphoma. The most common type was diffuse large B-cell lymphoma (DLBCL), which accounted for 17 of the localized and 4 of the disseminated cases. Burkitt's lymphoma (BL), three being disseminated, was found in four patients. There were six extranodal marginal zone lymphomas (ENMZL), three being localized. Seven DLBCL and one BL showed additional histological features of mucosa-associated lymphoid tissue (MALT) lymphoma. Localized aggressive lymphomas treated with surgery and/or radiation therapy had relapse rates of 100% and 67%, respectively. Cyclophosphamide, hydroxydaunomycin, vincristine, and prednisone (CHOP)-like chemotherapy with or without local irradiation led to 17% relapses in patients with localized aggressive lymphoma. Median follow-up time was 32 months (0.6-218); 37% of the patients relapsed and 24% had progressive disease. Response to salvage regimens, given to 91% of the patients with recurrent disease, was poor. The 2-year overall survival rate was 63%, 72% for patients with localized disease, and 46% for patients with disseminated lymphoma. The majority of breast lymphomas are localized aggressive lymphomas that should be treated initially with CHOP-like chemotherapy with or without irradiation. The initial choice of treatment is very important because response to salvage regimens is poor.

Diffuse large B-cell lymphoma of the stomach: assessment of microsatellite instability, allelic imbalance, and trisomy of chromosomes 3, 12, and 18.

Several types of genetic aberrations including microsatellite instability (MSI), allelic imbalance (AI), and chromosomal trisomies have been reported in low-grade (LG) mucosa-associated lymphoid tissue (MALT)-type gastric lymphomas. Presence of such genetic alterations could be a discriminator between de novo large cell lymphoma and high-grade (HG) MALT-type lymphoma. We investigated 17 primary gastric large B-cell lymphomas with and without features of MALT-type lymphoma for MSI, AI, and presence of trisomy of chromosomes 3, 12, and 18. We studied resection specimens from 17 primary gastric extranodal diffuse large B-cell lymphomas. Cases classified as HG MALT-type lymphoma, based on either the presence of LG MALT-type lymphoma component in the background (L/H MALT) or large cell lymphoepithelial lesions (HG MALT), and diffuse large B-cell lymphoma (DLBCL-NOS) when no features of MALT were present. MSI was analyzed using fluorescently labeled polymerase chain reaction primers (D3S11, D6S262, D3S1261, D3S1262, D3S1265). Paired tumor and normal DNA samples were amplified, and PCR products were analyzed on a DNA sequencer (ABI PRISM 373XL) with GeneScan (Applied Biosystems, Foster City, CA). MSI was defined as a gain of a novel-length allele compared with the corresponding normal tissue. AI was assessed at locus 3q27 (D3S1262 and D3S1265). The cases were analyzed for the presence of trisomy of chromosomes 3, 12, and 18 using interphase fluorescence in situ hybridization. MSI was detected in 4 out of 15 (27%) cases from which DNA was amplifiable with all primers and all MALT-type lymphomas. In two cases (13%), MSI was present at two loci sufficient to be classified as high-frequency MSI (MSI-H); this was seen exclusively in HG MALT lymphomas (P = 0.04). In the remaining two cases, MSI was detected at a single locus (low-frequency MSI). Allelic imbalance at the locus D3S1262 was detected in 4 out of 17 (24%) cases. It occurred more commonly in stage IE lymphomas when compared with higher stages (P = 0.03), regardless of lymphoma subtype. Trisomy 12 was detected in 3 out of 17 cases (18%) exclusively in stage IE lymphomas (P = 0.08). MSI was uncommon and was found exclusively in MALT-type lymphomas. MSI-H was even less common but occurred in HG MALT lymphomas only. Allelic imbalance at 3q27 (D3S1262) and trisomy 12 were found more commonly in low-stage disease. The latter two findings are in concordance with the recent suggestion that the published variation in gain of chromosomal material in high-grade gastric lymphomas may be related to stage rather than to the subtype of lymphoma. Because of the relatively low frequency of MSI in the high-grade B-cell lymphomas of the stomach, this feature cannot be used to reliably discriminate between the histologic types of extranodal diffuse large B-cell lymphoma.

甲状腺ＭＡＬＴリンパ腫の細胞像

目的:甲状腺原発MALTリンパ腫と橋本病の鑑別を目的として細胞像を検討した.方法:甲状腺原発のMALTリンパ腫の8例および橋本病の5例を用いて各種細胞の出現率を算定した. 免疫組織化学により免疫グロブリン軽鎖のモノクロナリティーを確認した.成績:橋本病では小リンパ球が優位であったが, MALTリンパ腫では中型リンパ球が主体を占めた. 中型リンパ球はくびれた核と淡明な細胞質を有していた. 形質細胞, 類形質細胞も混在し認められた. 細胞標本においてもlymphoepithelial Iesion (LEL), follicular colonizationを示唆する所見が認められた. LELはMALTリンパ腫に特異的な所見で穿刺吸引細胞標本においても確認できた.結論:MALTリンパ腫と橋本病との鑑別には, 細胞の出現率を算定し主体をなす細胞を把握すること, 細胞形態の詳細な観察ならびにLELを見つけることが有用と考えられた.

Mucosa-associated lymphoid tissue in human efferent tear ducts.

The recent description of primary marginal zone lymphomas in human efferent tear ducts with typical features of lymphomas arising in mucosa-associated lymphoid tissue (MALT) infers the presence of MALT in the human efferent tear ducts. To date, studies have not established clearly whether organised MALT occurs in normal human efferent tear ducts. To elucidate this problem, efferent lacrimal pathways from unselected body donors with unknown prior history of efferent tear duct, ocular, or nasal disease were examined for the presence of organised MALT. Organised lymphoid tissue was found with the cytomorphological and immunophenotypic features of MALT in 41% of the cases examined. These findings suggest that MALT is a feature that, although it need not be present in normal efferent tear ducts, is acquired during life in a proportion of apparently asymptomatic individuals.

Gastric lymphoma of mucosa-associated lymphoid tissue and Helicobacter pylori.

Although the majority of primary gastric lymphomas are of high-grade non-Hodgkin's type, a significant number are low-grade B cell lymphomas. The recognition that the majority of the latter have characteristic clinicopathological features that are different from those of their nodal counterparts has led to the suggestion that these lymphomas arise specifically from within organized extranodal lymphoid tissue; this tissue resembles that seen constitutively in the intestine (mostly located in the terminal ileum as Peyer's patches) and is termed mucosa-associated lymphoid tissue (MALT). The paradox of this proposal is that there is no MALT in the gastric mucosa in normal individuals from which a primary lymphoma can arise. However, it has been shown that organized lymphoid tissue with all the features of MALT can be acquired in the gastric mucosa, and this is seen most frequently, but not exclusively, in association with infection by Helicobacter pylori (H. pylori). Subsequent studies have confirmed a close association between H. pylori infection and gastric MALT lymphoma with the infection preceding the development of the lymphoma. In vitro studies have demonstrated that there is an immunologically based drive to tumor cell proliferation in low-grade gastric MALT lymphomas associated with the presence of H. pylori. Clinical studies have shown that, at least in early lesions, eradication of the organism can result in tumor regression in 60 to 92% of cases.

Lymphoma of the thyroid gland.

Lymphoma of the thyroid is uncommon but its exact incidence is unknown. Thyroid lymphoma almost always arises against a background of Hashimoto’s thyroiditis, the relative risk of a patient with Hashimoto’s thyroiditis developing lymphoma being 67 (Holm et al. 1985). In 1984 Isaacson and Wright noted close histological and clinical similarities between low-grade B-cell lymphomas of the stomach, salivary gland, lung and thyroid. The histological features of these lymphomas appeared to recapitulate those of mucosa-associated lymphoid tissue (MALT), as typified by Peyer’s patches, and the term “MALT lymphoma” was coined to describe this group of extranodal lymphomas (Isaacson and Wright 1984). Unlike the other common sites where MALT lymphomas occur, the thyroid cannot be described as a mucosal organ. As the MALT concept has developed, however, it has become clear that the common theme is not necessarily that the lymphomas arise in mucosae but, rather, that they arise from acquired lymphoid tissue with features of MALT; these include lymphoid follicles and adjacent epithelium containing intraepithelial B-cells, the so-called lymphoepithelium. Functionally, MALT differs from nodal lymphoid tissue in that antigens gain access directly across the lymphoepithelium rather than via afferent lymphatics.

Laryngeal lymphoma derived from mucosa-associated lymphoid tissue.

Extranodal lymphomas account for as many as 40% of non-Hodgkin's lymphomas, and most arise in the gastrointestinal tract, but other mucosal organs may be involved, especially the upper aerodigestive tract. Low-grade B-cell lymphomas arising in the gastrointestinal tract and other mucosae have been found to recapitulate the structure and cytologic features of mucosa-associated lymphoid tissue (MALT). Histologically low-grade MALT lymphomas are characterized by centrocyte-like B-cells with a phenotype similar to that of so-called marginal zone B-cells. Tumors evolving from MALT are generally rare among lymphomas of the upper aerodigestive tract, but a few cases of laryngeal lymphomas derived from MALT have been reported. Primary MALT lymphoma of the larynx should always be considered in tumors with histopathologic features of low-grade B-cell lymphoma, or so-called pseudolymphoma.

Mantle cell lymphoma with the features of mucosa-associated lymphoid tissue (MALT) lymphoma in an HTLV-I-seropositive patient

Mantle cell lymphoma with the features of mucosa-associated lymphoid tissue (MALT) lymphoma in an HTLV-I-seropositive patient

Follicular dendritic cells in extranodal non-Hodgkin lymphomas of MALT and non-MALT type

Extranodal lymphomas of the thyroid (n = 19), kidney (n = 15) and testis (n = 30) were investigated histologically and immunohistochemically for follicular dendritic cell pattern using the monoclonal antibody Ki-FDClP. This recognizes follicular dendritic cells in paraffin sections. Follicular dendritic cells were most predominant in lymphomas of the thyroid. These thyroid lymphomas showed the morphological features of mucosa-associated lymphoid tissue (MALT) type lymphomas in 18 of 19 cases and were classified as high-grade malignant lymphoma of MALT type with evidence of a low-grade malignant component (n = 18). Ten of these cases contained destroyed reactive follicles of follicular dendritic cells. In 6 of these 10 cases follicular dendritic cells occurred in a pattern of tumour-associated abortive follicle type. The remaining lymphoma of the thyroid was an immunoblastic lymphoma of B-cell type showing no detectable follicular dendritic cells. In extranodal lymphomas of non-MALT type follicular dendritic cells occurred in only two cases where immunocytoma involved the kidney. Malignant lymphomas of the kidney (chronic lymphocytic leukaemia, n = 2; immunocytoma, n = 4; centroblastic lymphoma, n = 9) and of the testis (immunocytoma, n = 2; centroblastic lymphoma, n = 27; immunoblastic lymphoma of B-cell type, n = 1) revealed no characteristics of MALT type lymphoma, cytologically or with respect to follicular dendritic cells. Classical lymphoepithelial lesions formed by centrocyte-like cells, a hallmark of MALT, occurred exclusively in thyroid lymphomas of MALT type. Although occurrence of classical lymphoepithelial lesions formed by centrocyte-like cells was limited to thyroid lymphomas of MALT type, a growth pattern of lymphoid blasts, with formation of lesions mimicking lymphoepithelial lesions superficially, was found in 6 of 27 testicular centroblastic lymphomas. Follicular dendritic cells in non-Hodgkin's lymphomas of MALT type show distinct follicular patterns not found in other extranodal lymphomas such as those found in the kidney and testis.

Helicobacter pylori-associated gastritis and primary B-cell gastric lymphoma

Although lymphoid tissue is absent in normal gastric mucosa, primary lymphomas arise in the stomach and most of these recapitulate the features of mucosa-associated lymphoid tissue (MALT). Gastric lymphoid tissue is known to be acquired in response to local infection by Helicobacter pylori,and we have confirmed this in 450 patients with H pylori-associated gastritis of whom 125 showed mucosal lymphoid follicles. In 8 patients, B lymphocytes infiltrated epithelium, which is a feature characteristic of MALT. We also examined 110 cases of gastric MALT lymphoma and found H pyloriinfection in 101 of these (92%). We conclude that gastric MALT is acquired in H pylori infection and that this provides the necessary background in which MALT lymphoma might develop.