ABSTRACT
Marginal zone lymphomas (MZLs) include extranodal MZL of mucosa-associated lymphoid tissue (MALT lymphoma), nodal MZL (NMZL), and splenic MZL (SMZL). MALT lymphoma is the most common type of lymphoma involving the gastrointestinal (GI) tract (location in the stomach being the most frequent) [1–5]. Other common sites of involvement include salivary gland, skin, lung, thyroid gland, and orbital area. Gastric MZL (or MALT lymphoma) usually remains localized for long periods within the tissue of origin. Bone marrow (BM) involvement at presentation is uncommon [4,6]. Disseminated disease appears to be more common in non-GI MALT lymphomas [7,8]. MALT lymphomas harboring t(11;18) are unlikely to transform to a higher grade lymphoma [9–11], but exceptions may occur. The t(11;18) positive lymphomas usually lack the chromosomal aberrations and microsatellite alterations frequently seen in the translocation-negative MALT lymphomas. Elevated lactate dehydrogenase, advanced stage, and high-risk IPI score are associated with poorer outcome [12]. The patients without lymph node involvement at presentation have a 5-year survival of 97%, and those with nodal involvement have 75% 5-year survival. The involvement of multiple mucosal sites at diagnosis did not appear to change the outcome [7]. The presence of monoclonal gammopathy in extranodal MZL correlates with advanced disease and BM involvement [13]. Gastric MALT lymphoma responds to Helicobacter pylori eradication therapy [1,14,15]. Factors associated with a lack of response to antibiotic treatment include deep penetration of the gastric wall, a t(11;18)(q22;q21), and a lack of H. pylori infection [1,16,17]. Lymphomas with deep mural involvement at presentation are often positive for t(11;18) [17]. Large-cell transformation occurs in 8% of MALT lymphomas [18].
