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t(11;18)(q21;q21) is a specific chromosomal translocation associated with mucosa-associated lymphoid tissue (MALT) lymphoma. It fuses the amino terminal of the API2gene to the carboxyl terminal of the MALT1gene and generates a chimeric fusion product. Although the translocation is frequently detected in gastric and pulmonary MALT lymphoma, its incidence in MALT lymphomas from other sites is largely unknown. It also remains unknown whether the occurrence of the translocation is influenced by the nature of preceding diseases associated with MALT lymphomas. We screened for t(11; 18)(q21;q21) in 417 cases of MALT lymphoma from 8 major sites by reverse transcription–polymerase chain reaction. t(11;18)(q21;q21) was found at highest frequencies in MALT lymphomas from the lung (38%) and stomach (24%), and at moderate frequencies in those from the conjunctiva (19%) and orbit (14%). However, the translocation was found only rarely in MALT lymphomas from the salivary gland (1%) and was absent in those from the thyroid, skin, liver, and other rare sites, and in immunoproliferative small intestinal disease (IPSID). In gastric MALT lymphoma, t(11;18)(q21;q21) was significantly associated with infection by CagA-positive strains of Helicobacter pylori. As CagA-positive strains of H pyloriare much more potent in induction of host inflammatory responses, including activation of neutrophils, which release highly genotoxic oxygen reactive species, we therefore examined neutrophil infiltration in recognized precursors of MALT lymphoma including H pylori–associated gastritis, lymphoepithelial sialadenitis, and Hashimoto thyroiditis. Neutrophil infiltration was prominent in H pylori–associated gastritis but not in lymphoepithelial sialadenitis and Hashimoto thyroiditis. Our results demonstrate that t(11;18)(q21; q21) occurs at markedly variable frequencies in MALT lymphoma of different sites and suggest that the occurrence of the translocation is influenced by the nature of premalignant diseases associated with MALT lymphoma. Oxidative damage might play a role in development of t(11;18)(q21; q21).

In approximately 5% to 10% of gastric mucosa–associated lymphoid tissue (MALT) lymphomas, evidence ofHelicobacter pyloriinfection is absent, and their pathogenesis is poorly understood. We reviewed the clinical data and histology, and we examined t(11;18)(q21;q21) and BCL10 expression pattern in 17 such cases. In each case, the absence ofH pyloriwas confirmed by negative serology and histology/immunohistochemistry. Five cases with stage IEdisease were first treated with antibiotics, and none of them showed any endoscopic or histologic response. Review of the histology failed to identify any apparent difference between gastric MALT lymphomas with and withoutH pyloriinfection. Reverse transcription–polymerase chain reaction (RT-PCR) showed t(11;18)(q21;q21) in 9 (53%) of 17 cases, more frequent in lymphomas at stage IIEor above (5 of 6) than those at stage IE(3 of 10). Two t(11;18)(q21;q21)-positive lymphomas were treated by partial gastrectomy and more than 16 years later showed lymphoma relapse in the gastric stump with dissemination to other mucosal sites, poorly responsive to therapy. BCL10 nuclear expression was observed in 7 of 8 t(11;18)(q21;q21)-positive cases and 4 of 7 t(11;18)(q21;q21)-negative cases, including one case suspicious for a BCL10-involved chromosomal translocation. Our results show that t(11;18)(q21;q21) occurs at a high frequency inH pylori–negative gastric MALT lymphomas. Translocation-positive gastric MALT lymphomas tend to be aggressive, and patients with such lymphomas might benefit from prompt treatment and close follow-up.

In approximately 5% to 10% of gastric mucosa–associated lymphoid tissue (MALT) lymphomas, evidence ofHelicobacter pylori infection is absent, and their pathogenesis is poorly understood. We reviewed the clinical data and histology, and we examined t(11;18)(q21;q21) and BCL10 expression pattern in 17 such cases. In each case, the absence of H pylori was confirmed by negative serology and histology/immunohistochemistry. Five cases with stage IEdisease were first treated with antibiotics, and none of them showed any endoscopic or histologic response. Review of the histology failed to identify any apparent difference between gastric MALT lymphomas with and without H pylori infection. Reverse transcription–polymerase chain reaction (RT-PCR) showed t(11;18)(q21;q21) in 9 (53%) of 17 cases, more frequent in lymphomas at stage IIE or above (5 of 6) than those at stage IE (3 of 10). Two t(11;18)(q21;q21)-positive lymphomas were treated by partial gastrectomy and more than 16 years later showed lymphoma relapse in the gastric stump with dissemination to other mucosal sites, poorly responsive to therapy. BCL10 nuclear expression was observed in 7 of 8 t(11;18)(q21;q21)-positive cases and 4 of 7 t(11;18)(q21;q21)-negative cases, including one case suspicious for a BCL10-involved chromosomal translocation. Our results show that t(11;18)(q21;q21) occurs at a high frequency in H pylori–negative gastric MALT lymphomas. Translocation-positive gastric MALT lymphomas tend to be aggressive, and patients with such lymphomas might benefit from prompt treatment and close follow-up.

Characteristic chromosomal aberrations have been associated with subtypes of non-Hodgkin's lymphoma with distinct clinicopathologic features. Low-grade B-cell lymphomas of mucosa-associated lymphoid tissue (MALT) form such a group and might be expected to be characterized by a specific cytogenetic abnormality. Metaphase analyses of MALT lymphoma are rare due to problems with fresh tissue collection and poor in vitro proliferation. However, the small number of published series suggests that chromosome trisomies, particularly trisomy 3, might be characteristic of these tumors. The application of interphase cytogenetic techniques to routinely processed material allows the examination of a large series of archival cases and is particularly useful for the demonstration of chromosome trisomies. We have used this technique to analyze 70 cases of low-grade MALT lymphoma from various sites and found trisomy 3 in 60%. This finding compares with 16% in low-grade nodal B-cell lymphoma and 27% in primary splenic lymphoma of marginal zone type (splenic lymphoma with villous lymphocytes). These results provide further evidence that low-grade MALT lymphomas from all sites form a single pathologic entity distinct from nodal B-cell lymphomas. Although MALT lymphoma and primary splenic lymphoma may arise from marginal zone B cells, they are genetically distinct.