Clinically occult breast cancer. Multicentricity and implications for treatment.

Two hundred thirty-two biopsies have been performed for nonpalpable mammary lesions, detectable by mammography, but not clinically apparent. Sixty-two malignancies were demonstrated within this group, including thirty invasive ductal cancers, seven minimally invasive ductal cancers, 20 noninvasive ductal cancers, and five lobular carcinomas-in situ. When mastectomy specimens were examined for evidence of multifocal cancer in quadrants other than that in which the primary was located, 39.6% of the breasts examined demonstrated evidence of multifocal cancer ductal or lobular, invasive or non-invasive. These findings suggest that any therapeutic procedure for invasive or noninvasive ductal cancer which does not include total mastectomy may leave behind foci of cancer which may be a threat to the patient.