Low grade gastric B-cell lymphoma of mucosa associated lymphoid tissue in immunocompromised patients.

An increased incidence of non-Hodgkin's lymphoma is seen in patients with immunodeficiency from any cause. The majority of these are high grade B-cell lymphoma and most are associated with the Epstein-Barr virus (EBV). In post-transplant lymphoma/lymphoproliferative disorders the tumour may regress following reduction of immuno-suppression but in AIDS the lymphomas show a characteristic aggressive course and poor prognosis. We describe low grade B-cell gastric lymphoma of mucosa associated lymphoid tissue (MALT) in three immunocompromised patients (two post-transplant, one HIV positive). In each case, the tumour showed classical morphological features of gastric MALT lymphoma and was not associated with EBV. Helicobacter pylori was identified in each case. Clinical follow-up suggests that the behaviour in these tumours is similar to that seen in MALT lymphomas in immunocompetent patients and not typical of the lymphomas usually associated with immunosuppression. Although the finding of MALT lymphoma in immunosuppressed patients might be coincidental, the association of some MALT lymphomas with autoimmune disease suggests that dysregulation of the immune system might play a role in the pathogenesis of these tumours.