Table 3 Histological and immunohistochemical criteria useful in the distinction between gastric mucosa associated lymphoid tissue lymphoma and gastritis.

• Marginal zone distribution pattern

• Lymphoepithelial lesions

• Follicular colonisation

• Overgrowth of plasma cells in the tips of the lamina propria by ascending CD20+ tumour cells

• Lack of active gastritis

• Infiltration of the muscularis mucosae

• Plasma cell differentiation with Ig light chain restriction