The introduction of breast-conserving treatment for patients with early stage breast cancer has led to renewed interest in the pattern and extent of microscopic involvement of cancer within a breast containing a grossly apparent tumor. In a landmark paper that appeared in this journal 10 years ago, Holland et al.' from Nijmegen, The Netherlands, reported the findings of a detailed radiographic-histologic evaluation of the breast in 264 mastectomy specimens from patients with clinically unifocal breast cancer measuring 4 cm or smaller. The evaluation was performed by sectioning each mastectomy specimen into 5-mm-thick slices, radiographing these slices, and examining histologically all grossly and radiologically suspicious areas as well as random sections from each quadrant and the nipple. This technique allowed precise mapping of the extent and distribution of residual carcinoma in relation to the palpable (or reference) tumor. In only 40% of cases was the cancer in the breast restricted to the palpable tumor. Nineteen percent of cases had additional foci of cancer restricted to the immediate 2 cm around the tumor. Forty-one percent of the cases showed cancer foci farther than 2 cm from the reference tumor, including 27% in which the additional foci were entirely intraductal and 14% in which they were invasive and intraductal. This study demonstrated that residual cancer is frequently present in the breast after gross excision of the tumor, that this residual cancer is principally in the vicinity of the tumor, and that it is usually intraductal in nature.
In a parallel series of !studies from our group, among patients with Stages I and 11' breast cancer treated with conservative surgery consisting of a limited breast re-