MALT lymphoma pathology, initial diagnosis, and post-treatment evaluation

Mucosa-associated lymphoid tissue (MALT) lymphomas are extranodal marginal zone B-cell lymphomas arising at various sites and account for 7–8% of adults’ non-Hodgkin’s B-cell lymphomas. MALT lymphomas reproduce features of the mucosa-associated lymphoid tissue that is present at the physiological level in the terminal ileum and constitute the Peyer’s patches. The diagnosis of MALT lymphoma relies on three characteristic histopathological features reminiscent of Peyer’s patches: a diffuse infiltrate of centrocyte-like (CCL) neoplastic lymphoid cells, lymphoepithelial lesions and reactive non-neoplastic lymphoid follicles. MALT lymphoma is usually multifocal, and numerous small tumor foci may be seen throughout the gastric mucosa at distance from the main tumor mass. MALT lymphoma of the lung results in an interstitial thickening by a nodular lymphoid infiltrate composed of CCL lymphoid cells with a typical marginal zone distribution around reactive lymphoid follicles. Synchronous occurrence of gastric MALT lymphoma and gastric adeno-carcinoma has been reported in several studies.