What causes cysts, fibrocystic, or "lumpy" breasts?
Fibrocystic breast condition involves the glandular breast tissue. The sole known biologic function of these glands is the production, or secretion, of milk. Occupying a major portion of the breast, the glandular tissue is surrounded by fatty tissue and support elements. The glandular tissue is composed of different types of cells: (1) clusters of secretory cells (cells that produce milk) that are connected to the milk ducts (tiny tubes); and (2) the cells that line the surfaces of the secretory cells, called the epithelial cells.
The most significant contributing factor to fibrocystic breast condition is a woman's normal hormonal variation during her monthly cycle. Many hormonal changes occur as a woman's body prepares each month for a possible pregnancy. The most important of these hormones are estrogen and progesterone. They directly affect the breast tissues by causing cells to grow and multiply.
Many hormones aside from estrogen and progesterone also play an important role in causing fibrocystic breasts. Prolactin, growth factor, insulin, and thyroid hormone are some of the other major hormones that are produced outside of the breast tissue, yet act in important ways on the breast. In addition, the breast itself produces hormonal products from its glandular and fat cells. Signals that are released from these hormonal products are sent to neighboring breast cells. The signals from these hormone-like factors may, in fact, be the key contributors to the symptoms of fibrocystic breast condition. These substances may also enhance the effects of estrogen and progesterone and vice versa.
The same cyclical hormones that prepare the glandular tissue in the breast for the possibility of milk production (lactation) are also responsible for a woman's menstrual period. However, there is a major difference between what happens in the breast and uterus.
In the uterus (the womb), these hormones promote the growth and multiplication of the cells lining the uterus. If pregnancy does not occur, this uterine lining is sloughed off and discharged from a woman's body during menstruation.
In the breast, these same hormones stimulate the growth of glandular breast tissue. They also increase the activity of blood vessels, cell metabolism, and supporting tissue. All this activity may contribute to the feeling of breast fullness and fluid retention that women commonly experience before their menstrual period.
When the monthly cycle is over, however, these stimulated breast cells cannot simply slough away and pass out of the body like the lining of the uterus. Instead, many of these breast cells undergo a process of programed cell death, called apoptosis. During apoptosis, enzymes are activated that start digesting cells from within. These cells break down and the resulting cellular fragments are then further broken down by scavenger cells (inflammatory cells) and nearby glandular cells.
During this process, the fragments of broken cells and the inflammation may lead to scarring (fibrosis) that damages the ducts and the clusters (lobules) of glandular tissue within the breast. The inflammatory cells and some of the breakdown fragments may release hormone-like substances that in turn act on the nearby glandular, ductal, and structural support cells.
The amount of cellular breakdown products, the degree of inflammation, and the efficiency of the cellular cleanup process in the breast vary from woman to woman. These factors may also fluctuate from month to month in an individual woman. They may even vary in different areas of the same breast.