Fourteen primary non-Hodgkin's malignant lymphoma (ML) of the breast observed between 1985 and 1989 were reviewed. Using the Ann Arbor staging system, 5 of these ML were at clinical stage IE, 2 at stage IIE, and only one was at clinical stage IVE (the ML involved both breasts of a young woman after her third post-partum and she died quickly), staging was not available in 6 cases. At the time of physical examination, the diagnosis of ML was not suspected. When possible, it was done or-suspected before surgery, studying fine needle aspiration cytology (4 cases) or drill biopsy (2 cases). Cytological examination was also useful to make the difference between primary large cells T ML and granulocytic sarcomas which sometimes occur before the acute myeloid leukemia and/or the blast crisis of a myeloproliferative disorder. According to the Kiel histopathological classification (updated in 1988), 78.5% of these ML were of great malignancy, more than half of them being polymorphous centroblastic B ML. Only one of them was an angiocentric pleomorphic T lymphoma of great malignancy. None of the ML of low malignancy, all of the follicular type, was a MALT (Mucosa Associated Lymphoid Tissue) ML, as described by Isaacson. Intra-epithelial lymphocytes were observed in 6 of the ML of great malignancy; but in 2 cases, they were T lymphocytes and these lympho-epithelial lesions could not be interpreted as an argument for the MALT nature of these ML. None of our cases were associated with a ML from another MALT site.