Relationship between the Extent of Intraductal Component and That of the Invasive Component in Ductal Carcinomas of the Breast

To clarify the relationship between the extent of the intraductal component and the invasive component in cases of invasive ductal carcinoma (IDC) of the breast, we divided 87 such cases into two groups, Group I in which the intraductal component extended for less than 10 mm (36 cases) and Group II in which the intraductal component extended for 10 mm or more (51 cases). On histological slides, there was an association between the extent of the intraductal component and the pattern of invasion. The majority (80.6%) of Group I IDC cases showed an invasive component composed of one invasive nodule, whereas 62.7% of Group II IDC cases showed an invasive component composed of two or more such nodules. On gross and microscopical examination, Group II IDC showed a significantly larger mean tumor size than Group I IDC (23.4 +/- 8.9 mm vs. 18.3 +/- 6.6 mm, P less than 0.002 & 24.1 +/- 14.1 mm vs. 17.1 +/- 6.5 mm, P less than 0.002). A similar result was obtained by clinical examination (41.8 +/- 17.0 mm vs. 29.5 +/- 11.6 mm, P less than 0.0001). These results suggest that Group II ductal carcinomas may frequently develop multiple stromal invasion, resulting suddenly in a sizeable breast mass perceived by the patient.