To investigate 4 cases of primary lymphoma of the breast and review previous studies in a search for any preoperative characteristics that could assist the diagnosis of lymphoma of the breast. Retrospective study. University hospital, Israel. 4 women. Accurate diagnosis before operation. No special characteristics for early diagnosis of primary malignant lymphoma of the breast were found. The predominant involvement of right breast in primary lymphoma of the breast should be noted. Even though primary lymphoma of the breast is rare, there are no laboratory or imaging signs of early diagnosis. Excisional biopsy or Tru-cut biopsy are the only correct methods of diagnosis.