Ductal carcinoma in situ (DCIS): a revised concept.

The in situ concept was introduced in an effort to clarify the transition between benign epithelium and invasive cancer, and for that reason it focused on histologic changes. Lobular carcinoma in situ was first described in these terms and continues to be considered a purely microscopic lesion that never makes a mass in the breast. A very different situation exists in cases of ductal carcinoma in situ (DCIS), because both gross and microscopic disease exists together. As a result, it has been difficult to evaluate competing treatment options for the DCIS lesion. This study was undertaken to better characterize patients with DCIS lesions. Seventy consecutive patients with DCIS who underwent treatment at our institution were analyzed and two subgroups were identified. The method of presentation and the distribution of cancer in the breast as well as in the regional lymph nodes were examined. The study shows that differentiation between gross and purely microscopic DCIS is feasible and must be accomplished if treatment recommendations are to be made on a rational basis.