DISEASE CHARACTERISTICS: Histologically confirmed unilateral stage I invasive breast cancer No more than 1 tumor and no greater than 2 cm Grade 1 tumor of any histological type OR No special type OR Mixed type allowed No lymph node involvement No in situ carcinoma only or ductal carcinoma in situ with microinvasion No vascular invasion No Paget's disease of the nipple Well differentiated special type of primary mammary carcinoma including: Tubular Tubular/cribriform Cribriform Papillary Mucoid No lobular, medullary, or other rarer types of mammary carcinomas including: Adenoid cystic Carcinoid Secretory Spindle cell Apocrine No distant metastases Hormone receptor status: Not specified