OBJECTIVES: I. Determine the tumor response in women with stage IV breast cancer who achieve partial remission after a mini-conditioning regimen comprising fludarabine and cyclophosphamide, followed by allogeneic peripheral blood stem cell transplantation (PBSCT), and donor lymphocyte infusion (DLI). II. Determine the progression free survival in patients who achieve complete remission after this treatment regimen. III. Determine whether DLI exerts graft versus tumor effect in these patients. IV. Determine the acute and delayed toxicities of this regimen in these patients. V. Determine the rates of durable hematologic engraftment in patients treated with this regimen. VI. Determine the incidence and severity of acute and chronic graft versus host disease in patients treated with this regimen. VII. Determine the extent of chimerism in patients treated with this nonmyeloablative conditioning regimen. VIII. Determine the rate and quality of immune reconstitution in patients treated with this regimen. IX. Determine the event free and overall survival in patients treated with this regimen.