Before we jump into a full discussion of breast tumors, we need to review the anatomy and function of the female breast. Although 2 % of all breast cancers do occur in men, DCIS rarely does.
The function of the female breast is to supply our young with milk. During pregnancy and after birth, special breast cells, the lobule cells, will secrete milk. When the baby suckles, the milk lobules secrete the milk and it is carried down to the nipple through a series of ducts. Many of these structures too small to be seen without a microscope.
Here is a representation of a healthy lobule and duct as it might be seen under the microscope:
In a non-diseased lobule all the lobular cells look identical. The same is true for the healthy duct cells. The basement membrane is a thick connective tissue outer sleeve that holds all these cells in place. If we cut across a duct, and look at it on end through the microscope, we could see a hollow tube, lined with cells that all look alike, with an outer sheath, the basement membrane ( see insert above).