A 46-year-old patient was referred for a right mammary nodule associated with a chronic mastopathy. Cytological examination suggested an inflammatory process but frozen sections concluded to carcinoma with lymphoid stroma. Histological examination found characteristic features of MALT lymphoma: reactive lymphoid follicles, lymphoplasmocytoid lymphoid proliferation and lymphoepithelial lesions. Immunohistochemistry and in situ hybridation revealed a monotypic IgGk immunoglobulin. Molecular biology techniques found a rearrangement of IgH locus. Lymphocytic perigalactophoritis was found in the remaining breast tissue. After 33 months, no tumoral recurrence occurred. Primary MALT lymphoma of the breast is exceptional and its histogenesis is unclear. The role of pre-existent inflammatory lesions in the genesis of this tumour is not established. Our observation illustrates the diagnostic difficulty and the usefulness of complementary techniques in this diagnosis. The existence of inflammation close to tumour is interesting to emphasize.