Gastric marginal zone lymphoma of MALT type: ESMO clinical practice guidelines for diagnosis, treatment and follow-up

incidence Extranodal marginal zone lymphomas of mucosa-associated lymphoid tissue (MALT) type represent ∼7% of all non-Hodgkin's lymphomas in the western world and can arise at any extranodal site. At least one-third of them present as a primary gastric lymphoma, which in approximately two-thirds of cases is associated with a chronic Helicobacter pylori infection [1]. diagnosis The most common presenting symptoms of a gastric MALT lymphoma are non-specific upper gastrointestinal complaints that often lead to an endoscopy usually revealing non-specific gastritis or peptic ulcer with mass lesions being unusual [2, 3]. Diagnosis is based on the histopathological evaluation of the gastric biopsies [III, A]. The diagnosis should be in accordance with the current World Health Organisation (WHO) classification and accurate assessment of a potential associated large B-cell lymphoma is essential [4]. The diagnosis should, therefore, be confirmed by an expert haematopathologist [5]. It should be noted that the term ‘high grade MALT lymphomas’ is no longer accepted in the current WHO classification, hence cases with solid or sheet-like proliferation of transformed large cells have to be diagnosed as diffuse large B-cell lymphoma [4]. Differentiation from other indolent lymphomas is not always straightforward and a minimum immunohistochemistry panel should include CD20, CD10, CD5 and cyclin D1 [IV, B]. It is noteworthy that lymphoepithelial lesions, despite being very typical of MALT lymphoma, are neither essential for the diagnosis nor pathognomonic, as they can be seen under some reactive conditions as well as in other lymphoma subtypes. If the presence of active H. pylori infection is not demonstrated by histochemistry, it must be ruled out by serology, urea breath test and/or stool antigen test [5, 6]. In addition to routine histology and immunohistochemistry, fluorescence in situ hybridisation studies for detection of t …