Molecular diagnostics in low-grade gastric marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue type after Helicobacter pylori eradication therapy

The primary gastric lymphomas are extranodal non-Hodgkin's lymphomas that l ikely originate from the mucosa-associated lymphoid tissue (MALT). Data sug gest that chronic infection with Helicobacter pylori (H pylori) is signific antly associated with the pathogenesis of low-grade gastric MALT lymphomas. This is in keeping with the observation that many patients with early low- grade MALT lymphomas have complete remissions after H pylori eradication th erapy. However, the stability of these remissions remains unclear and relap ses have been reported. It can be difficult to distinguish between early ma lignant and benign disorders of the gastric mucosa. A polymerase chain reac tion (PCR) assay can detect rearrangements of the variable region of immuno globulin heavy chains. This assay can be used to distinguish the clonality of B lymphocytes and has been investigated as a test for differential diagn osis of MALT lymphomas. Monoclonality is observed in the majority of MALT-l ymphoma samples at diagnosis but has been found in gastritis samples as wel l. Whether the presence of monoclonal B cells is associated with the risk o f lymphoma progression remains unclear. As many as 50% of patients who have complete histologic remissions of MALT lymphoma after H pylori eradication therapy have persisting monoclonal bands in follow-up PCR monitoring. Alth ough it is unclear as to whether monoclonality indicates the presence of mi nimal residual disease, patients who have persistent monoclonal bands durin g follow-up should be considered at risk for relapse. The PCR assay for rea rrangements of the variable region of the immunoglobulin heavy-chain gene a ppears to be of low value in the diagnosis of B-cell malignancies but could provide a useful tool in the follow-up of patients who achieve remissions after H pytori eradication.