The breast epithelium is the cellular tissue lining the milk-producing ducts of the breast. These cells form the first line of defense against the rampant proliferation of breast cancer. Up to 80 percent of all breast tumors originate in breast epithelial cells. Depending on the severity of malignant tissue growth, there are several ways that oncologists can sample epithelial breast tissue in order to prevent widespread growth of the damaged epithelial cells into the healthy cells lining the ducts.
The first sign that breast epithelium is breaking down occurs when the genes of normal epithelial cells are damaged. Normally, there is a gene within the cells that produces antibodies to cancerous cells and another gene which maintains a balance between the number of cells being born and dying. When these genes are destroyed through some environmental agent, the epithelial cells are no longer able to form a continuous defensive boundary around the milk-producing ducts, and cancerous cells proliferate.
Several techniques are used to collect, observe, and identify precancerous cells from the compromised breast epithelium, including ductal lavage, fine needle aspiration, and biopsy. Fine needle aspiration is a safe procedure in which a hollow needle is inserted into a suspected area and a group of cells is carefully removed. A biopsy is a more radical procedure in which a substantial amount of tissue is cut out of breast epithelium when a mass has already been discovered.
Ductal lavage is a technique used to prevent cancerous cells from traveling beyond a single duct into new duct tissue. It is only used in breasts that produce fluid when suction is applied to the duct. A thin catheter injects a saline solution that frees some cells from the lining of the duct before suction commences. Upon examination, the removed fluid may contain some precancerous cells.
As people age, their tissue reproduces more slowly and shrinks. The more the breast tissue shows signs of slower growth and shrinkage with age, called involution, the lower the rate of cancer of the breast epithelium. The greater the breast tissue density, which is the number of cells per cubic area of the breast, the better the that chance a single cell will malfunction and become cancerous. Though estrogen has been singled out as a possible cause of breast cancer, the action of estrogen itself has been found to both promote survival in some cases and encourage cancer cell proliferation in others.