Invasive ductal carcinoma of the breast with a predominant intraductal component: cooperative clinicopathologic study in seven Japanese centers.

A nationwide multicenter joint study was undertaken to investigate the clinicopathologic characteristics of invasive ductal carcinoma of the breast with a predominant intraductal component, a diagnostic entity proposed in the histologic typing of breast tumors by the World Health Organization in 1981. A total of 368 tumors, of which 218 were studied pathologically between 1983 and 1987 and 150 between 1971 and 1977, were accumulated for the present study from seven medical institutes in Japan. The incidence of such types of tumor was higher in the latter period than in the former, as was that of pure intraductal carcinomas. Seventy of the 368 tumors displayed metastatic nodal involvement and nine tumor deaths were observed from 150 tumors followed up for over 10 years following radical mastectomy, the overall quantity of the extraductal stromal invasion clearly acting on lymph node metastases and patients' outcome. We consider a total stromal invasion of greater than 5 mm to be critical in the prognosis of patients with tumor of this type.