Beta-2-microglobulin levels in patients with extranodal B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT)-type: a retrospective analysis.

Background: Serum levels of beta-2 microglobulin (B2M) have been reported as a predictor of clinical outcome, prognosis and tumor burden in patients with various types of lymphomas. In case of lymphoma of the mucosa-associated lymphoid tissue (MALT)-type, no clear data exist to define the role of B2M in terms of staging or prognosis. In a retrospective analysis we investigated the serum B2M-levels in patients suffering from histologically verified MALT-type lymphoma in correlation to stage and response to treatment.

Patients And Methods: All patients admitted to our institution since 1996 with a diagnosis of MALT-type lymphoma were retrospectively evaluated for staging procedures and measurements of serum B2M levels. Patients with a staging work-up including otorhinolaryngologic evaluation, gastroscopy with multiple biopsies, endosonography of the upper GI-tract, enteroclysis, colonoscopy, CT of thorax and abdomen and bone marrow biopsy were analysed, while staging was performed according to the Ann Arbor system as modified by Musshoff. In addition, only patients with histologic samples amenable to re-assessment by a reference pathologist were included.

Results: A total of 68 patients with a diagnosis of MALT-type lymphoma were identified from our records. However, only in 32 patients exact staging according to our inclusion criteria had been performed and serum B2M-levels prior to the initiation of therapy were available in all these patients. Twenty-five patients; suffered from gastric lymphoma, while the remaining 7 patients had extragastric manifestations. In total, 13 out of 32 patients presented with stage I disease, 17 patients were rated as stage II and 2 patients suffered from stage III disease. Nineteen patients had elevated B2M-levels prior to therapy: 6 patients were rated as stage 1, II had stage II and two had stage III disease. Five patients still had elevated B2M-levels following treatment despite radiologically and histologically verified complete remission.

Conclusion: In this series, no correlation between serum B2M levels, tumor burden and clinical outcome was apparent in patients with MALT-type lymphomas. While the number of patients with disseminated disease was small we could not demonstrate a difference for B2M-levels between stage I and stage II. While we cannot rule out that B2M might be different in patients with stage I/II disease as compared to more advanced disease, further investigations are necessary to determine the role of this marker in patients with MALT-type lymphoma.