RATIONALE: Biopsy is the removal of cells or tissue for examination under a microscope. It is not yet known which type of breast biopsy is more effective for diagnosing breast lesions.

PURPOSE: Randomized diagnostic trial to compare the effectiveness of two different types of biopsy in patients who have breast lesions that cannot be felt upon examination.

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.

OUTLINE: This is a randomized study. Patients are randomized to one of two diagnostic arms. Arm I: Patients undergo radiographic placement of a radioactive seed (either iodine I 125 or palladium Pd 103) into the suspicious lesion. Patients then undergo surgery to remove the lesion along with the seed and a small margin of surrounding breast tissue followed 3 months later by a postoperative mammogram. Arm II: Patients undergo a needle localized breast biopsy with a specimen x-ray.

DISEASE CHARACTERISTICS: Suspicious nonpalpable breast lesion requiring breast biopsy for diagnosis OR Nonpalpable breast lesion that is not amenable to core needle biopsy or advanced breast biopsy instrumentation (ABBI) excision Hormone receptor status: Not specified

PATIENT CHARACTERISTICS: Age: 18 and over Menopausal status: Not specified Performance status: Not specified Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Not specified Renal: Not specified Other: Not pregnant

PRIOR CONCURRENT THERAPY: Not specified