Ductal carcinoma in situ is a noninvasive breast lesion that affects ectatic segmental ducts. Cells are polygonal, rounded, cuboidal, or columnar. Cells may form a cribriform micropapillary or a solid architecture.
Mitotic figures are uncommon, but can be atypical.
The various morphologic subtypes can include solid, cribriform, micropapillary, or clinging variants. Of these subtypes, the micropapillary variant distinguishes itself by association with multifocal occurrence in the breast. An especially prognostically favorable in situ tumor is the encysted papillary carcinoma in pure form, for which local excision is considered curative. Low-grade DCIS is associated with a 10 fold risk for subsequently developing invasive breast cancer in the same breast. The risk of cancer increases with age.