Extranodal Marginal Zone Lymphoma of MALT-type (MALTOMA)
A dense monomorphic lymphoid infiltrate in the submucosa along with the background remnants of oxyntic glands. Immunohistochemical findings of gastric marginal zone lymphoma are similar to nodal examples of the disease, and include positivity for CD20, CD79a, CD21, CD35, BCL2 and surface immunoglobulins. They are negative for CD5, CD10, CD23, and cyclinD1. About one-third of gastric MALTOMAS possess t(11;18) translocation which results in API2-MALT1 fusion. Such cases do not respond to anti-Helicobacter therapy and are also less likely to transform to large B-cell lymphomas.