Concepts regarding the best methods for doing biopsies and the most appropriate methods for treatment of patients with breast cancers have changed dramatically since the early nineteen seventies. Currently formal biopsies (incisional or excisional) are being done as two-step procedures with reliance on permanent sections for diagnosis. The advantages of this type of biopsy are discussed along with the increasing frequency of doing them under local anesthesia on an out-patient basis. Informal biopsies (fine needle aspiration or needle core) are becoming increasingly popular in the office and clinic and stereotactic biopsies are receiving increasing attention. The use of flow cell cytometry to complement cytologic diagnosis and the use of needle localization, with or without dye injection, for the biopsy of occult lesions are described. The need for determining by prognostic parameters and by scanning the remaining breast for residual cancers after radiolabeled monoclonal antibody injection, which in situ cancers can be managed by lesser procedures than total mastectomy and which early invasive cancers can be managed by just wide excision is discussed. The two main current local-regional therapy options for women with invasive breast cancers (some type of modified mastectomy with breast reconstruction and breast conservation with radiotherapy) are presented in detail. The present need of doing an axillary dissection in both for staging is discussed along with the future possibility of eliminating it by scanning with a gamma-camera the axillary and internal mammary nodal areas after radiolabeled monoclonal antibody injection.(ABSTRACT TRUNCATED AT 250 WORDS)