Update on MALT lymphomas

doi:10.1016/j.beha.2004.08.003

Best Practice & Research Clinical Haematology

Volume 18, Issue 1, March 2005, Pages 57-68

https://doi.org/10.1016/j.beha.2004.08.003 Get rights and content

Gastric mucosa associated lymphoid tissue (MALT) lymphoma is a histologically distinct tumour derived from MALT acquired as a result of Helicobacter pylori infection. Eradication of H. pylori causes clinical regression of the lymphoma in 75% of cases. In seeking to identify those cases resistant to this therapy, and in the interests of further understanding the biology of MALT lymphoma, genetic alterations of MALT lymphomas have been investigated. Three translocations, t(11;18)(q21;q21), t(1;14)(p22;q32) and t(14;18)(q32;q21) are specifically associated with MALT lymphoma and the genes involved have been identified. T(11;18) results in a chimeric fusion between the API2 and MALT1 genes and is specifically associated with gastric MALT lymphomas that do not respond to eradication of H. pylori. T(1;14) and t(14;18) deregulate BCL10 and MALT1 expression, respectively. These three chromosomal translocations that involve different genes appear to share common oncogenic properties by targeting the same nuclear factor κB (NFκB) oncogenic pathway.

Section snippets

Epidemiology

MALT lymphoma comprises 7–8% of all B-cell lymphomas and at least 50% of primary gastric lymphomas.2., 3. Most cases occur in adults with a median age of 61 years and a slight female predominance, which is more marked in salivary gland MALT lymphoma. There is a higher incidence of gastric MALT lymphoma in north-eastern Italy probably related to a high prevalence of Helicobacter pylori associated gastritis in that region.⁴ A special sub-type of small intestinal MALT lymphomas, known as

Aetiology

MALT lymphomas only rarely arise from native MALT; they more usually arise from MALT that has been acquired as a result of a chronic inflammatory disorder (see below) at sites normally devoid of MALT, such as the stomach, salivary gland, lung, thyroid and ocular adnexa. MALT lymphomas of the salivary gland and thyroid, organs normally containing no lymphoid tissue, are always preceded by lymphoepithelial (myoepithelial) sialadenitis (LESA)6., 7., 8. usually associated with Sjögren's syndrome

Molecular genetics

A number of genetic alterations have been identified in MALT lymphomas including trisomy 3²⁸, p53 mutation/LOH²⁹, and p16 deletion.³⁰ More recently, three specific translocations, t(11;18)(q21;q21)31., 32., t(1;14)(p22;q32)³³, and t(14;18)(q32;q21)34., 35. have been recognised in MALT lymphomas. T(11;18)(q21;q21) results in a chimeric fusion between the API2 and MALT1 genes36., 37., 38., whereas t(1;14)(p22;q32) and t(14;18)(q32;q21) cause deregulated expression of BCL1039., 40. and MALT34., 35.

Summary

MALT lymphomas are a subgroup of low-grade B-cell lymphomas that arise from extranodal sites that have accumulated MALT as a result of a chronic inflammatory disorder. Subsequent work clarified the interrelationship between gastric MALT lymphoma and H. pylori resulting in the novel treatment of gastric lymphoma using antibiotics. More recently, three chromosomal translocations have been found to characterise MALT lymphoma, their frequency at least in part depending on the site of origin of the