Primary lymphoma of the breast is an uncommon malignant breast tumor which is seldom distinguished preoperatively from other more common forms of breast cancer. Bilateral breast lymphoma affects younger women especially during pregnancy or postpar­tum. We report a case of a 55-year-old woman who was admitted to our hospital with painless bilateral breast enlargement. A bilat­eral radical mastectomy with bilateral axillary lymph node dissection was performed. The histology of the surgical specimen was non-Hodgkin's malignant lymphoma of the diffused large B cell type. Most of the neoplastic cells resembled large centrocytes and sometimes blast cells showing some degree of plasmacytoid differentiation. Foci with a sufficient number of immunoblasts were also noted. The patient was also found to have a bilateral axillary lymph node metastasis. After additional clinical and laboratory screening, there was no other evidence of lymphatic disease at other sites. The patient was submitted to the anticancer hospital for further treatment. She was free of recurrence two years after surgery. The rarity of the disease, lack of uniform classification and variable treatment modalities make prognostic predictions of breast lymphoma difficult.