OBJECTIVES: I. Compare the effect of low dose radioactive seed localized breast biopsy versus needle localized breast biopsy on operative time and tissue loss in patients with nonpalpable breast lesions. II. Compare the cost effectiveness of these diagnostic methods in these patients. III. Demonstrate that radioactive seed localization allows for elimination of specimen x-ray in these patients. IV. Demonstrate that radioactive seeds may be placed safely for 1-7 days prior to surgical removal in these patients.