The extent and distribution of cancer in breasts with palpable primary tumors.

The term multicentricity has been employed to describe cancer cells beyond the borders of the primary tumor. However, it is not clear if there are multiple independent sites of origin or if the process simply represents spread of the cancer. The present study was designed to examine the distribution and extent of cancer in the breast and identify factors that bear on these events. All mastectomy specimens between 1980 and 1983 were systematically examined by means of multiple sections. One hundred seventy-nine of 657 patients (27%) were found to have separate foci. The most common histologic type (invasive ductal) was least likely to have multifocal disease (19%), while it was extremely common in the small group of patients with intraductal lesions (81%). Size was a factor in ductal but not in lobular lesions. Ninety per cent of the secondary foci were found in close proximity to the primary, suggesting spread rather than multicentricity. This implies a more limited and predictable distribution of cancer cells and opens the way to more rational selection and surgical preparation of patients for breast preservation.