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 API2 gene to the carboxyl terminal of the MALT1 gene 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 pylori are 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).