Gastric low-grade mucosa-associated lymphoid tissue lymphomas: their histogenesis and high-grade transformation

[Studies on clinicopathological features of duodenal-type follicular lymphoma of 18 patients]

To investigate the clinical and pathological characteristics of duodenal-type follicular lymphoma (D-FL), and to deepen the understanding of Duodenal-type follicular lymphoma. The clinical symptoms, endoscopic features, pathologic features, immunophenotype, molecular pathological features and treatment follow-up of 18 D-FL patients diagnosed in Department of Pathology, Beijing Tiantan Hospital affiliated to Capital Medical University between January 2020 and July 2023 were summarized. A total of 18 patients with D-FL were included, including 10 males and 8 females. The median age was 49 (32-69) years respectively. Most of the patients were found during gastroenteroscopy or presented with the common gastrointestinal symptoms of stomach pain, acid reflux, vomiting and diarrhea. Most endoscopic findings were multiple small gray and white polyposis. In the pathological morphology, the mucous layer and submucous layer showed lymphoid follicular structures with full and strained follicles. The immunophenotype showed that the tumor cells strongly expressed CD20 and BCL2 and had low proliferation activity. Immunoglobulin clonal analysis of 1 case showed IgK monoclonal rearrangement (1/1). FISH showed 1 case of BCL2 gene rearrangement (1/3). All patients did not receive targeted chemotherapy and adopted a wait-and-see strategy. Median follow-up was 12 (2-34) months. This study shows that D-FL is an indolent lymphoma, which tends to occur in the duodenum and has a good prognosis.

CT and MR imaging findings of ocular adnexal mucosa-associated lymphoid tissue lymphoma associated with IgG4-related disease: multi-institutional case series

AIM

To report CT and MR imaging findings of ocular adnexal mucosa-associated lymphoid tissue lymphoma associated with IgG4-related disease (IgG4-MALT lymphoma), a rare but clinically important complication of ocular adnexal IgG4-related disease.

METHODS

We retrospectively reviewed all cases of histologically confirmed ocular adnexal IgG4-related disease at three tertiary and one secondary referral centers, between February 2003 and December 2016. Seven cases of histopathologically diagnosed IgG4-MALT lymphoma were identified. CT and MR images were analyzed by consensus of two experienced head and neck radiologists.

RESULTS

Lacrimal glands were the main site of involvement in all seven patients. The lesions typically showed well-demarcated margins, iso- to hyperattenuation on precontrast CT, T2 hypo- to isointensity, T1 isointensity, and homogenous internal architecture with homogenous enhancement pattern. Lesions were mostly hyperdense and isointense to normal extraocular muscles on postcontrast CT and MR images, respectively.

CONCLUSION

Unlike in typical ocular adnexal IgG4-related disease, T2 isointensity and hyperattenuation on precontrast CT images were noted in some IgG4-MALT lymphoma cases. Although the findings may be nonspecific, the possibility of accompanying MALT lymphoma may need to be considered, when ocular adnexal lesions in patients clinically suspected of having IgG4-related disease are refractory to glucocorticoids and show T2 isointensity and hyperattenuation on precontrast CT for the optimal management of the patients. However, this is a case series of a very rare complication of ocular adnexal IgG4-related disease, and thus caution is warranted to generalize the conclusion.

Radiotherapy alone for stage IE ocular adnexal mucosa-associated lymphoid tissue lymphomas: long-term results

Background

To evaluate the long-term efficacy and toxicity of radiation therapy in patients with Stage IE primary ocular adnexal mucosa-associated lymphoid tissue lymphoma.

Methods

We designed a retrospective analysis to evaluate 81 patients with ocular adnexal mucosa-associated lymphoid tissue lymphoma treated with radiation therapy between 2006 and 2016. The median radiation dose was 30 Gy (range, 30–36 Gy in 15–18 fractions). Local control, progression-free survival, overall survival, and cumulative incidence of Grade 3 cataract were calculated by using the Kaplan–Meier method.

Result

The median follow-up time was 74 months (range, 4–157 months). The 5-year local control was 100%. Although local relapse was suspected in 3 patients after radiation therapy, 2 patients were pathologically diagnosed as IgG4-related inflammation and in 1 patient as intense inflammatory cell infiltration. The 5-year progression-free survival was 94.4%. Five patients had relapse at distant sites. The 5-year overall survival was 98.8%. Twenty patients had Grade 3 cataract. The 5-year cumulative incidences of Grade ≥ 3 and Grade ≥ 2 cataract for 58 patients treated without a lens shield were 38 and 40%, respectively. The incidence of Grade ≥ 3 cataract was 42% for 50 patients treated with 6-MV X-rays (estimated lens dose: 29 Gy) and 17% for 8 patients treated with 9-MeV electrons (estimated lens dose: 24 Gy).

Conclusions

Radiation therapy alone yielded excellent local control and long-term survival in Stage IE ocular adnexal mucosa-associated lymphoid tissue lymphoma. Long-term observation with careful attention to relapse at distant sites is necessary. In the case of suspected local relapse, IgG4-related disease should be carefully ruled out.

Immunoglobulin G4 (IgG4)-Positive Ocular Adnexal Mucosa-Associated Lymphoid Tissue Lymphoma and Idiopathic Orbital Inflammation

PURPOSE

To report clinical and pathological characteristics of idiopathic orbital inflammation and ocular adnexal mucosa-associated lymphoid tissue (MALT) lymphoma with immunoglobulin G4 (IgG4)-positive plasma cells.

METHODS

A retrospective histopathological review and clinical case series. A total of 51 biopsy samples from January 2005 to December 2015 were used in this study, including 21 cases of biopsy-confirmed idiopathic orbital inflammation and 30 cases of biopsy-confirmed ocular adnexal MALT lymphoma. Most cases of ocular adnexal lymphoma were conjunctival tissue. Retrospective immunohistochemical studies were performed to estimate the IgG4 and IgG4/IgG ratios. Histopathologic features, demographic and clinical data, radiologic findings, treatment, and follow-up information for each patient were analyzed.

RESULTS

Among idiopathic orbital inflammation, 6 (28.6%) of the 21 patients were diagnosed as "probable" ocular adnexal IgG4-related diseases and 13 (43.3%) of the 30 patients were diagnosed as MALT lymphoma with IgG4-positive plasma cells. Six cases of 13 IgG4-positive MALT lymphoma group had contralateral chronic inflammatory lesions infiltrated by IgG4-positive plasma cells, which was significantly (p = 0.007) higher than that in the IgG4-negative group. Conjunctival involvement was 69% of the IgG4-positive MALT lymphoma cases. Bilateral involvement of the ocular adnexa was significantly (p = 0.02) more frequent among IgG4-positive MALT lymphoma patients than that in IgG4-positive idiopathic orbital inflammation patients. Recurrence rate in the IgG4-positive group was higher (p = 0.05) than that in the IgG4-negative group but not significantly.

CONCLUSIONS

This study presented an unusual framework of ocular adnexal IgG4-related inflammation, in conjunctiva. It is important to understand contralateral chronic inflammatory lesions and their relationship with IgG4-positive MALT lymphoma. Tissue biopsy and IgG4 immunostaining are required for all cases because IgG4-positive MALT lymphoma can arise from a pre-existing IgG4-positive chronic inflammatory lesions. This is the first study that performs IgG4 immunostaining for tissue from a relatively large number of conjunctival MALT lymphomas in a single center. Therefore, it will help to diagnose conjunctival lymphoproliferative disease.

The role of radiotherapy in the treatment of gastric mucosa-associated lymphoid tissue lymphoma

Purpose

To assess radiotherapy for patients with early stage gastric mucosa-associated lymphoid tissue (MALT) lymphoma with respect to survival, treatment response, and complications.

Materials and Methods

Enrolled into this study were 48 patients diagnosed with gastric MALT lymphoma from January 2000 to September 2012. Forty-one patients had low grade and seven had mixed component with high grade. Helicobacter pylori eradication was performed in 33 patients. Thirty-four patients received radiotherapy alone. Ten patients received chemotherapy before radiotherapy, and three patients underwent surgery followed by chemotherapy and radiotherapy. One patient received surgery followed by radiotherapy. All patients received radiotherapy of median dose of 30.6 Gy.

Results

The duration of follow-up ranged from 6 to 158 months (median, 48 months). Five-year overall survival and cause-specific survival rates were 90.3% and 100%. All patients treated with radiotherapy alone achieved pathologic complete remission (pCR) in 31 of the low-grade and in three of the mixed-grade patients. All patients treated with chemotherapy and/or surgery prior to radiotherapy achieved pCR except one patient who received chemotherapy before radiotherapy. During the follow-up period, three patients developed diffuse large B-cell lymphoma in the stomach, and one developed gastric adenocarcinoma after radiotherapy. No grade 3 or higher acute or late complications developed. One patient, who initially exhibited gastroptosis, developed mild atrophy of left kidney.

Conclusion

These findings indicate that a modest dose of radiotherapy alone can achieve a high cure rate for low-grade and even mixed-grade gastric MALT lymphoma without serious toxicity. Patients should be carefully observed after radiotherapy to screen for secondary malignancies.

Review of the molecular profile and modern prognostic markers for gastric lymphoma: how do they affect clinical practice?

Primary gastric lymphoma is a rare cancer of the stomach with an indeterminate prognosis. Recently, a series of molecular prognostic markers has been introduced to better describe this clinical entity. This review describes the clinical importance of several oncogenes, apoptotic genes and chromosomal mutations in the initiation and progress of primary non-Hodgkin gastric lymphoma and their effect on patient survival. We also outline the prognostic clinical importance of certain cellular adhesion molecules, such as ICAM and PECAM-1, in patients with gastric lymphoma, and we analyze the correlation of these molecules with apoptosis, angiogenesis, tumour growth and metastatic potential. We also focus on the host-immune response and the impact of Helicobacter pylori infection on gastric lymphoma development and progression. Finally, we explore the therapeutic methods currently available for gastric lymphoma, comparing the traditional invasive approach with more recent conservative options, and we stress the importance of the application of novel molecular markers in clinical practice.

Clinical study of mucosa-associated lymphoid tissue lymphomas of the head and neck

BACKGROUND

Limited information is available on mucosa-associated lymphoid tissue lymphomas arising in the head and neck.

METHOD

A retrospective analysis was conducted of 20 patients who were histologically diagnosed with mucosa-associated lymphoid tissue lymphoma and treated at our institution between January 1990 and December 2009.

RESULTS

Treatment consisted of surgical resection alone in two patients (10 per cent), surgical resection with consecutive radiotherapy in one (5 per cent), and radiotherapy alone in eight (40 per cent). Three patients (15 per cent) were treated with systemic chemotherapy, and three (15 per cent) received chemoradiotherapy. Three patients (15 per cent) were informed of the diagnosis but not treated for their condition.

CONCLUSION

All of the 20 patients were still alive after a mean follow-up period of 50.8 months. Local treatment for mucosa-associated lymphoid tissue lymphoma of the head and neck should be the first choice in early-stage disease. However, prolonged follow up is important to determine these patients' long-term response to treatment.

Primary gastrointestinal follicular lymphoma involving the duodenal second portion is a distinct entity: a multicenter, retrospective analysis in Japan

We conducted a multicenter, retrospective study to determine the anatomical distribution and prognostic factors of gastrointestinal (GI) follicular lymphoma (FL). This study included 125 patients with stage I and II(1) GI-FL. Of the 125 patients, the small intestine was examined in 70 patients, with double-balloon endoscopy and/or capsule endoscopy. The most frequently involved GI-FL site was the duodenal second portion (DSP) (81%), followed by the jejunum (40%); 85% of patients with involvement of the DSP also had jejunal or ileal lesions. The absence of abdominal symptoms and macroscopic appearance of multiple nodules were significantly present in the DSP-positive group. During a median follow up of 40 months, six patients showed disease progression. Patients with involvement of the DSP had better progression-free survival (PFS) than those without such involvement (P = 0.001). A multivariate analysis revealed that male sex, the presence of abdominal symptoms, and negative involvement of the DSP were independently associated with poor PFS. In conclusion, most patients with GI-FL have duodenal lesions associated with multiple jejunal or ileal lesions. Gastrointestinal follicular lymphomas involving the DSP might be a distinct entity showing a favorable clinical course.

Gastrointestinal dissemination of mucosa-associated lymphoid tissue lymphoma: computed tomographic findings

OBJECTIVE

To describe the computed tomographic findings of mucosa-associated lymphoid tissue (MALT) lymphoma with gastrointestinal (GI) tract dissemination.

METHODS

We retrospectively reviewed the computed tomographic findings for the location, morphology, contrast enhancement, and continuity of the involved bowel segment with ancillary findings in 10 patients with MALT lymphoma involving multiple GI tracts.

RESULTS

MALT lymphoma involved a total of 31 bowel segments. The gastric lesions appeared as segmental (n = 4) or diffuse (n = 1) wall thickening and the small- or large-intestinal lesions as circumferential wall thickening (n = 11) or localized polypoid mass (n = 8) with homogeneous and isoattenuating or hypoattenuating enhancement. Continuity of the involved bowel segment was present in 6 patients, bowel perforation in 1, lymphadenopathy in 8, and hepatosplenomegaly in 4.

CONCLUSIONS

Despite its rarity, MALT lymphoma can disseminate into the GI tract in the form of circumferential bowel wall thickening or localized polypoid mass with or without gastric involvement.

Point mutation of 5’ noncoding region of BCL-6 gene in primary gastric lymphomas

AIM: To investigate the mutations of the 5’ noncoding region of BCL-6 gene in Chinese patients with primary gastric lymphomas.

METHODS: PCR and direct DNA sequencing were used to identify BCL-6 gene mutations in the 5’ noncoding region in 29 cases of gastric diffuse large B-cell lymphoma (DLBCL) and 18 cases of gastric mucosa-associated lymphoid tissue (MALT) lymphoma as well as 10 cases of reactive hyperplasia of lymph node (LRH).

RESULTS: Six of 29 gastric DLBCLs (20.7%), 4 of 18 gastric MALT lymphomas (22.2%) and 1 of 10 LRHs(10%) were found to have mutations. All mutations were single-base substitutions and the frequency of single-base changes was 0.20×10^-2 -1.02×10^-2 per bp.

CONCLUSION: Point mutations in the 5’ noncoding region of BCL-6 gene are found in Chinese patients with primary gastric DLBCLs and MALT lymphomas, suggesting that they may, in some extent, participate in the pathogenesis of primary gastric DLBCLs and MALT lymphomas.

MUC1 mucin expression in follicular dendritic cells and lymphoepithelial lesions of gastric mucosa-associated lymphoid tissue lymphoma

Membrane-associated mucin MUC1 is expressed in various adenocarcinoma cells and active T lymphocytes. We tried to find out whether MUC1 is expressed in gastric mucosa-associated lymphoid tissue (MALT) lymphoma lesion. MUC1 was not expressed in infiltrating T lymphocytes; however, MUC1 was found on the cell surface of follicular dendritic cells (FDC) of germinal centers and in the epithelial cytoplasm of lymphoepithelial lesion (LEL) of the lymphoma, which were immunohistochemically detected by monoclonal antibodies DF3 and MY.1E12. MUC1 was also expressed in the FDC of control cases (gastrectomy specimen containing reactive lymphoid follicles, n = 10, MUC1/ DF3, 100%; MUC1/MY.1E12, 40%), and FDC in MALT lymphomas (n = 59) showed lower MUC1 expression rates (MUC1/ DF3, 32%; MUC1/MY.1E12, 0%) than the control (P < 0.001). Lymphoepithelial lesion in the low-grade MALT lymphomas (n = 23) showed a higher MUC1/DF3 expression rate (30%) than those in the high-grade MALT lymphomas (n = 36; 6%; P < 0.05). T lymphocytes in the surface mucosa were more frequent in MALT lymphoma (91.4 +/- 80.6/unit area) than those in the control (20.0 +/- 23.6) (P < 0.001). S100-positive dendritic cells around LEL were more frequent in the low-grade (19.0 +/- 9.4/unit area) than in the high-grade (11.7 +/- 9.7) (P < 0.005). This study demonstrated MUC1 mucin expression on FDC for the first time. Mucosa-associated lymphoid tissue lymphoma, especially low-grade, shows immunologically active state, where FDC MUC1 expression may be suppressed by some factors released from lymphoma cells. Further study to elucidate the pathogenetic role of MUC1 in MALT lymphoma is necessary.

Loss of expression of alpha4beta7 integrin and L-selectin is associated with high-grade progression of low-grade MALT lymphoma

Expression of adhesion molecule in low-grade B-cell mucosa-associated lymphoid tissue (MALT) lymphoma of the gastrointestinal tract has been reported in recent years, but these reports have primarily focused on low-grade gastrointestinal MALT lymphoma. In this study, we examined the lymphocytic homing receptor alpha4beta7 integrin, L-selectin, and VLA-4 and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) in low-grade lymphoma of the gastrointestinal tract and other organs such as the ocular adnexa and thyroid. We also observed changes in the expression pattern associated with high-grade transformation. Neoplastic cells in the gastrointestinal low-grade lymphoma and the low-grade component of high-grade MALT lymphoma were found to be alpha4beta7 integrin(+), L-selectin(+), whereas the gastrointestinal high-grade component and diffuse large B-cell lymphoma were found to be alpha4beta7 integrin(-), L-selectin(-). High endothelial venules in the gastric MALT lymphomas expressed MAdCAM-1. In the ocular adnexa low-grade MALT lymphoma, most cases were alpha4beta7 integrin(-), L-selectin(+); and in the thyroid, most cases of both low- and high-grade MALT lymphoma were alpha4beta7 integrin(-), L-selectin(-). These findings show that alpha4beta7 integrin and L-selectin may play an important role in the lymphocyte homing of gastrointestinal low-grade MALT lymphoma and in the loss of alpha4beta7 integrin expression throughout the course of high-grade progression.

Gastrointestinal lymphoma: prevention and treatment of early lesions

Gastrointestinal lymphomas comprise a group of distinct clinicopathological entities. Differences in lifestyle and environmental factors between countries could account for the variety in the distribution of the main subtypes: low-grade B-cell lymphomas of the mucosa-associated lymphoid tissue type, alpha-chain disease and enteropathy (coeliac disease)-associated T-cell lymphoma (EATL). The possibility of preventing these lymphomas implies a knowledge of their natural history together with an identification of potential predisposing factors. The development of the lymphoid hyperplasia and subsequently low-grade lymphoma with the possibility of high-grade transformation is a multifactorial process involving both antigenic and host-related factors. The pathogenic role of Helicobacter pylori and gluten has been demonstrated in gastric lymphoma and enteropathy-associated T-cell lymphoma respectively, while environmental factors, especially non-specific bacterial ones, may play a major role in the pathogenesis of alpha-chain disease. The most difficult task in preventing these lymphomas is the recognition of early lesions likely to regress after the removal of the exogenous stimulus.

Multiple organ mucosa-associated lymphoid tissue lymphomas often involve the intestine

BACKGROUND

Low grade mucosa-associated lymphoid tissue (MALT) lymphomas usually are confined to single extranodal organs. Although some case reports have been published, clinicopathologic characteristics of multiorgan MALT lymphomas remain unclear.

METHODS

The authors evaluated 7 MALT lymphoma cases involving multiorgans in the past 7 years. In this period, they experienced 304 cases of MALT lymphomas. They analyzed the clinicopathologic features of these cases, including examination of clonal comparison among the lesions.

RESULTS

The patients, 4 females and 3 males, were aged 55-68 years old (average, 60.1 years). Four cases showed multiple organ involvement at the initial diagnosis or after a short period. In the other three cases, primary foci were the stomach, thyroid gland, and ocular adnexa; after a rather long period (3 years or more), distant metastases were found. Although intestinal primary lymphomas are rather rare, six of the seven cases showed large intestinal involvement. Lymph node involvement was proven in only three cases. The patients were rather resistant to the various therapeutic approaches. Although six patients are alive, five are with disease. DNA analyses revealed that in five of the cases evaluated, identical clones were detected among the different affected organs.

CONCLUSIONS

Multiorgan MALT lymphomas are rather rare. Most cases probably derived from a single clone, and lymphoma cells may selectively move among MALTs via a homing system with preferential involvement of the colon. Because multiorgan MALT lymphomas rarely achieve complete remission by treatment with combination chemotherapy or irradiation, MALT lymphomatous lesions should be checked carefully, especially in the large intestine.

Role of activated host T cells in the promotion of MALT lymphoma growth

Gastric mucosa-associated lymphoid tissue (MALT) B cell lymphomas contain activated helper T cells. The evidence supports the presence of mechanisms of T cell dependence underlying the development of these lymphomas. It appears that the T cells, which activate B cells, may contribute to lymphoma pathogenesis. Co-stimulatory molecules necessary for effective B cell/T cell interaction are expressed in MALT lymphomas. The studies suggest that CD40 signaling, in combination with cytokines, is essential for the development and progression of MALT lymphomas. Activated T cells of low grade gastric MALT lymphoma, while delivering full help to B cells, are apparently deficient in two cytotoxic mechanisms involved in the concomitant control of B cell growth.

Increased incidence of follicular lymphoma in the duodenum

The incidence of indolent lymphomas in the lymph nodes and extranodal regions is quite different. Follicular lymphoma (FL) is most common in the nodes, and it seems to be least common in the gastrointestinal (GI) tract, where mucosa-associated lymphoid tissue lymphoma arises most frequently. The authors report that the incidence of FL is unexpectedly high in the duodenum compared with other portions of the GI tract. FL was detected in only eight of 222 cases of GI lymphoma (3.6%). However, five cases of FL arose in the duodenum, which accounted for 38.5% of 13 duodenal lymphomas. Only in two patients did FL arise in either the stomach or the colorectum, and in the remaining patients FL was widespread with lymphomatous polyposis. Duodenal FL was composed of neoplastic follicles with small cleaved cells in dominance, and the immunophenotype of the lymphoma cells was CD10+, BCL-2+, CD20+, CD75+, CD79+, CD3-, CD5-, cyclin D1-, CD23-, and CD45RO-. All the patients were women age 37 to 66 years (average age, 52.4 yrs). In all patients the lymphoma was present around the ampulla of Vater, and four of five patients showed multiple small-size polyps. Although lymphoma cell infiltration was confined to the submucosa in the four patients examined, the regional lymph nodes were involved partially in two patients without distant metastasis. All patients are alive at 2 to 50 months of follow up (average, 27 mos), which is comparable with the prognosis for indolent nodal lymphomas. These results suggest that the duodenum has a distinct background of histogenesis of the lymphomas and that biopsy specimens from the duodenum with multiple polyps should be examined carefully.

Activation of the TCL1 protein in B cell lymphomas

The TCL1 gene, localized near the break point of chromosome 14q32.1 often involved in T cell leukemias, is also expressed in normal precursor T and B cells, and B cell lymphoma cell lines. We investigated the expression of the TCL1 protein in various types of B cell lymphomas according to the Revised European-American Classification of Lymphoid neoplasms. Paraffin-embedded tissue sections of lymphoma specimens were subjected to TCL1 immunohistochemistry, and positivity was scored on a three-tiered scale: - (< 25% cells), + (25-50% cells), and ++ (> 50% cells). The TCL1 protein was expressed in low-grade B cell lymphomas including mucosa-associated lymphoid tissue type in ocular adnexa (18/20, 90%). It was also expressed in follicular, lymphoplasmacytic, and mantle cell lymphoma, but not in high-grade diffuse large B cell lymphoma (2/11, 18%). These data suggest that the expression of the TCL1 gene characterizes low-grade B cell lymphomas, and may be involved in certain processes of lymphomatogenesis.

Detection of aberrant isotype switch recombination in low-grade and high-grade gastric MALT lymphomas

Gastric mucosa-associated lymphoid tissue (MALT) lymphoma originates from reactive lymphocytic infiltrates during chronic gastritis, closely associated with Helicobacter pylori infection. MALT lymphomas may be either “low grade” or “high grade,” and transformation from low grade to high grade can occur. To obtain information on the maturational state of MALT lymphoma cells, we investigated their ability to undergo isotype switch recombination, which together with immunoglobulin variable gene somatic mutation, contributes to normal B-cell maturation. Using specific probes for the immunoglobulin heavy-chain (IgH) switch regions, we found by Southern blot that 3 out of 5 low-grade cases and 2 out of 2 high-grade cases showed rearrangements within IgH switch regions, which appeared aberrant in 4 of the 5 cases. The cloning of two rearranged fragments from one low-grade and one high-grade case confirmed the aberrant nature of the rearranged fragments. A deletion from the switch μ region (Sμ) to the first constant μ exon (Cμ 1) and a second deletion from the second constant μ exon (Cμ 2) to the gamma 3 region (γ 3) was detected in the low-grade case. In the high-grade case, there was a deletion of the IgH intronic enhancer (Eμ) and a 336–base pair (bp) insertion into the Sμ region of a gene (KIAA0307) normally located at 15q24. These data demonstrate for the first time the ability of MALT lymphoma cells to undergo aberrant isotype switch recombinations, which might be directly involved in the development or progression of malignancy.

Primary low-grade gastric mucosa-associated lymphoid tissue (MALT) lymphoma with polypoid appearance. Polypoid gastric MALT lymphoma: A clinicopathologic study of eight cases

In the current study, we report eight cases with primary low-grade gastric mucosa-associated lymphoid tissue (MALT) lymphoma endoscopically characterized by polypoid lesions in order to highlight their clinicopathologic significance. Four patients were male, their ages ranging from 40 to 78 years old. The resected specimens revealed a histology of low-grade MALT lymphoma characterized by dense lymphocytic infiltration predominantly in the submucosa and a relatively monotonous proliferation of centrocyte-like cells with reactive follicles and infrequent lymphoepithelial lesions. The tumor cells were of CD5-, CD10-, CD20+, BCL2+ and cycline D1- phenotype, and showed a monoclonal rearrangement of immunoglobulin heavy chain genes in the five of six cases examined. Interestingly, Helicobacter pylori (H. pylori) was detected in three (37.5%) of the eight patients, which was significantly lower than previous reports. Two of the H. pylori-positive cases initially underwent H. pylori eradication, but showed no change in their lymphomas after the cure of H. pylori infection. The clinicopathologic findings of the present cases appeared to closely resemble those of colorectal MALT lymphoma with a polypoid appearance and few association of H. pylori infection in their pathogenesis. These gastric polypoid cases may merit separate consideration because of the therapeutic problems they pose.