RELATIONSHIP OF THE SIZE OF THE INVASIVE COMPONENT OF THE PRIMARY BREAST-CARCINOMA TO AXILLARY LYMPH-NODE METASTASIS

Background. Invasive ductal carcinomas of the breast frequently have a n intraductal (in situ) component at the tumor periphery that, in some cases, is included in the measurement of the tumor and thereby increa ses the size of the tumor beyond that of the invasive component. Metho ds. Thirty-seven ductal carcinomas containing intraductal and invasive components were analyzed. The total tumor size, the size of the invas ive component, the percentage of intraductal component, and the estima ted tumor volume were assessed for each tumor. Results. The mean size of the invasive component was 6.5 mm in axillary lymph node negative p atients and 14.3 mm in those with axillary lymph node metastasis (P = 0.0001). The mean total tumor size was 13.7 mm and 17.6 mm (P = 0.035) and the mean percent of intraductal component was 52% and 26% (P = 0. 015) in patients with negative and positive axillary lymph nodes, resp ectively. Ninety-two and four tenths percent of the difference in mean estimated total tumor volume between patients with negative and posit ive axillary lymph nodes was attributable to the difference in the vol ume of the invasive component alone. Conclusions. In small ductal carc inomas of the breast, the size of only the invasive component, as dete rmined by microscopic measurement, is a better predictor of axillary l ymph node status than is the total tumor size. The well established pr ognostic value of total tumor size largely is due to its reflection of the size of the invasive component.