Histologic criteria for the diagnosis of gastric low-grade malt lymphoma.

Low-grade B cell lymphoma of the stomach have the features of mucosa-associated lymphoid tissue (MALT) and is characterised by lymphoid hyperplasia and infiltrations of lymphocytes into glandular epithelium or lymphoepithelial lesions. It may be difficult to distinguish low-grade lymphomas from benign inflammatory lymphoid infiltrates. Nine primary gastric lymphomas and 20 benign lymphoid hyperplasia were investigated for the type of tumour cells, lymphoepithelial lesions. Dutcher bodies, cytologic atypia, the density of lymphoid infiltrates, invasion of the muscularis mucosae, germinal centers, reactive epithelial atypia and acute inflammation. Our results suggest that B cells proliferation, lymphoepithelial lesions, cytologic atypia and Dutcher bodies are very important for the diagnosis of low-grade MALT lymphoma. None of these was seen in inflammatory infiltrates. The presence of germinal centers, acute inflammation and reactive epithelial atypia does not exclude a diagnosis of low-grade gastric lymphoma.