Gastric low-grade mucosa-associated lymphoid tissue lymphomas: their histogenesis and high-grade transformation.
Gastric low-grade mucosa-associated lymphoid tissue (MALT) lymphoma is a unique disease. A vast majority of lymphoma cells are centrocyte-like cells or resemble monocytoid B cells, and occasionally show plasmacytic differentiation. Immunophenotypical and immunogenotypical examinations have indicated that they are in the differentiation stage of memory B cells, whose normal counterparts are marginal zone lymphocytes or monocytoid B cells in the lymphoid tissues. It arises from chronic gastritis closely associated with Helicobacter pylori (H. pylori) infection. Mucosa-associated lymphoid tissue lymphomas of other organs are also based on acquired MALT associated with chronic inflammation or autoimmune diseases. Interestingly, the majority of gastric low-grade MALT lymphomas regress by the eradication of H. pylori. The lymphoma cells, however, are not derived from B cells reacting with H. pylori itself but from autoreactive B cells. Although the mechanism of their oncogenesis has not been clarified, previous data suggest that autoreactive B cells proliferate in response to H. pylori-specific T cells, presumably with some cytokines. The genetic instability of such B cells then induces chromosomal abnormalities including trisomy 3 and/or other genetic changes. These B cells have the ability of autonomic proliferation and, even so, they might be sensitive to T cell stimuli. Low-grade gastric lymphomas occasionally progress to high-grade malignancy. The high-grade component of MALT lymphomas are composed of large-sized lymphoma cells that are morphologically indistinguishable from nodal large B cell lymphomas. This high-grade transformation is associated with p53 abnormalities or Bcl-6 overexpression. Gastric MALT lymphoma may provide a useful model in understanding multistep lymphomagenesis.
Department of Pathology, Okayama University School of Medicine, Japan. yoshino@okayama-u.ac.jp
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D000368:Aged; D015703:Antigens, CD / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology / Q000473:pathology; D002471:Cell Transformation, Neoplastic / Q000276:immunology / Q000473:pathology*; D006801:Humans; D018442:Lymphoma, B-Cell, Marginal Zone / Q000276:immunology / Q000473:pathology*; D008875:Middle Aged; D013274:Stomach Neoplasms / Q000276:immunology / Q000473:pathology*
D015703:Antigens, CD