[Lymphocytic proliferation in gastric mucosa]

There is the substantial problem as how to exactly define the minimal requirements for the diagnosis of a marginal zone B cell lymphoma of MALT type in the stomach. Consequently, there is vigorous disagreement in the literature whether or not clonal B cell proliferation exists in chronic gastritis. This situation was the starting point of a retrospective multicenter study of German/Swiss lymph node registries. The panel contributed gastric biopsies of 26 cases of consensually diagnosed gastric marginal zone lymphoma, 18 borderline cases and 53 cases of consensually diagnosed chronic gastritis. The Wotherspoon criteria were used and were found very appropriate in conjunction with CD20 immunohistology highlighting lymphoepithelial lesions. The gastritis cases scored Wotherspoon 1 or 2, the borderline cases 3 or 4, the lymphomas 5. Extensive PCR analysis, carried out independently at two institutions using two methodologies, revealed, 1., an excellent interinstitutional accordance in detection of clonality; 2., B cell clonality in 24/26 lymphoma cases, 4/18 borderline cases, and in 1/53 gastritis cases. Thus, "clonal gastritis", if existing at all, is exceedingly rare. Based on Wotherspoon criteria, the proposal is to define and proclaim a state of "B cell clonality of unknown significance, BCUS" for clonal cases scoring less than 5. "BCUS" should induce re-biopsies, and, in this special clinical setting, justifies a wachfull waiting strategy. Further, the problem of coexisting diffuse large B cell lymphoma in gastric MALT lymphoma is addressed and discussed. It is demonstrated why the panel dismissed the de Jong criteria as non-applicable in praxi.