导管原位癌是乳腺导管小叶系统内恶性上皮细胞的一种增殖，并且在显微镜下看不到通过基底膜浸润到周围基质的迹象。有些组织结构的形式是可以辨认的。最常见的有：粉刺状、筛状、实体状、微乳头状和乳头状（图１）。直到前不久，导管原位癌一直被认为是一种相对不常见的疾病，? Ductal carcinoma in situ is a proliferation of malignant epithelial cells within the ductal lobular system of the breast, and no signs of infiltration into the surrounding matrix through the basement membrane are visible under the microscope. Some forms of organizational structure are identifiable. The most common are: acne, ethmoid, solid, micropapillary, and papillary (Figure 1). Until recently, ductal carcinoma in situ has been considered a relatively uncommon disease.