Breast involvement in immunolymphoproliferative disorders: report of two cases of multiple myeloma of the breast.

Breast involvement by immunolymphoproliferative disorders is rare. Primary and secondary malignant lymphomas of the breast are much more common than multiple myeloma, of which only 16 cases have been described. We report two cases of patients with an established diagnosis of multiple myeloma in whom breast involvement appeared during the course of the disease. We underline diagnostic difficulties caused by the lack of clinical and radiological features which allow us to differentiate between breast carcinoma and breast involvement by lymphoproliferative disease. Only fine needle aspiration and/or excisional biopsy can differentiate between immunolymphoproliferative disorders and epithelial or mesenchymal tumors of the breast.