Significance and staging of nonpalpable carcinomas of the breast.

Current staging protocols for carcinoma of the breast do not contain precise definitions for cancers detected as suspicious mammographic findings only. We have examined the distribution of malignant lesions and the frequency of metastasis to the axillary nodes and multicentricity in 1,059 women who have undergone 1,132 biopsies of the breast for nonpalpable lesions in order to determine if nonpalpable carcinomas should be categorized and staged separately from those detected in the traditional manner. Of these 1,132 biopsies, 29.1 per cent (330) were malignant, including 190 invasive ductal carcinomas, 13 invasive lobular carcinomas, 81 in situ ductal carcinomas, 25 microinvasive ductal carcinomas, 20 instances of lobular carcinoma in situ and one instance of malignant carcinoid. None of the women with noninvasive or microinvasive carcinomas had axillary metastasis; however, of 167 women with invasive ductal or lobular carcinoma who underwent axillary dissection, 32.9 per cent had at least one positive axillary node. In those women in whom the invasive carcinomas presented as clustered calcifications, the likelihood of axillary metastasis was the same as in the women who had nonpalpable masses. The significant frequency of axillary metastasis in women with clinically occult cancers challenges the use of the term "minimal" to describe any invasive cancer, regardless of size. Although noninvasive and microinvasive ductal cancers may continue to be considered as "minimal," invasive cancers, regardless of presentation, should be staged according to their measured size on the mammograms that detect them.