Genetic Abnormalities in MALT Lymphoma

点击翻译按钮获取中文摘要

MALT lymphoma is generally associated with chronic inflammation. However, some tumors are independent of chronic inflammation, and positive for API2-MALT1 fusion gene. We performed the immunoglobulin heavy chain (IgH) gene analysis of gastric MALT lymphomas, and clarified that chronic inflammation-dependent tumors often used selected VH fragments, such as VH3-23 and VH3-30. In contrast, chronic inflammation-independent tumors used variegated VH fragments. This finding suggests that these two groups may be derived from different B-cell subsets, and progression from the former to the latter may not be a common pathway (Sakuma H, et al. Mod Pathol 2007). Thymic MALT lymphomas are closely associated with autoimmune disease. We analyzed these rare tumors for the IgH gene usage and found that they used VH fragments similar to those used in chronic inflammation-dependent gastric MALT lymphomas (Yoshida M, et al. J Pathol 2006). These data suggest that MALT lymphomas closely associated with ch … More ronic inflammation show restricted usage of VH fragments, and these tumors are genetically different from MALT lymphomas independent of chronic inflammation. Silencing of p16 gene has been associated with lymphoma progression. We analyzed p16 gene silencing in pulmonary MALT lymphomas and its clinicopathological significance. p16 gene was already silenced, mainly by gene hypermethylation, in many of the tumors at diagnosis, and this silencing was not correlated with any clinicopathological factors. This finding suggests that p16 gene silencing is associated with lymphomagenesis rather than lymphoma progression (Takino H, et al. Mod Pathol 2005). MALT lymphoma comprises up to 90% of primary pulmonary lymphomas, but its diagnosis is often difficult. API2-MALT1 fusion is specific to MALT lymphoma, and is detected in nearly half of the pulmonary cases. We performed a multiplex RT-PCR assay and successfully detected the fusion transcript using archival cytological specimens (BAL, sputum, and pleural effusion). Detection of API2-MALT1 fusion in these specimens would be useful as an ancillary assay for the diagnosis, staging, and follow-up of pulmonary MALT lymphoma (Inagaki H, et al. Int J Hematol 2005). We reported a case of oral MALT lymphoma that showed spontaneous regression (Sakuma H, et al. Pathol Int 2006), and cases that showed occurrence of diffuse large B-cell lymphomas after H. pylori eradication for MALT lymphomas (Iwano M, et al. Am J Gastroenterol 2006). Less