Extramammary tumors rarely metastasize to the breast. The commonest tumors to metastasize in breast tissue are lymphoproliferative diseases, melanoma, lung cancer and gynecological malignancies. Primary breast lymphoma has been reported in the literature with a maximum percentage of about 0.5% of all breast malignancies, while secondary localizations of lymphomas in the breast are less well studied in the literature than primary ones. The authors report a rare case of a secondary localization of B-cell chronic lymphocytic leukemia to the breast in which the diagnosis was obtained by histopathology and immunohistochemistry and further confirmed by molecular data. This occurrence must be considered in the differential diagnosis of a breast lump so that the primary hematological disease can be adequately treated and the correct type of breast surgery performed.