Mammographic identification and biopsy of occult breast cancer.

During a 9 year period we excised 70 suspicious non-palpable breast lesions detected by mammography. We found the most effective method of preoperative localisation to be insertion of a self retaining wire, and this procedure was facilitated by a Perspex grid incorporated in the mammography equipment. Thirty biopsies (43%) were found to be malignant, of which 14 contained invasive and 16 in situ carcinoma. The presence of malignancy could not be predicted from the mammographic appearance, although in situ cancer was always associated with microcalcification.