Fibrocystic Breast Condition
(Cysts, Fibrosis, Lumps)

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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 programmed 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.

Types of fibrocystic breasts

When biopsies (samples) of breast tissue are studied under the microscope, it is possible to identify different types of fibrocystic breast condition. Some cases of fibrocystic breast condition show little disturbance of the breast tissue. Other cases involve a large number of cysts, along with fibrous (scar) tissue, in the breast tissue. Additionally, in some cases of fibrocystic breast condition, the breast cells do not have a normal appearance.

Cysts and fibrosis: Usually, even when the breast is not stimulated to produce milk, some secretions are produced by the secretory glandular cells. These secretions are normally reabsorbed "downstream" in the ducts. However, when there has been tissue damage and scarring (fibrosis) in the breast, these secretions may be trapped in the glandular portions of the breasts, thereby leading to the formation of fluid-filled sacs called cysts. In some areas of the breasts, there may be excessive fluid secretions due to stimulation by hormone-like substances. The resulting cysts may remain microscopic or enlarge until they contain several teaspoons or even tablespoons of fluid. These larger cysts may be felt as palpable (capable of being detected by touching) breast lumps. Even microscopic cysts may sometimes be felt as palpable lumps if many cysts are clustered together and there is a buildup of fibrous (scar) tissue around the cysts.

Hyperplasia and atypical hyperplasia of breast cells: With repeated stimulation from normal hormones, and possibly the effects of many of the hormone-like substances produced in the breast, a few of the epithelial cells (cells that line the ducts in the breast) may eventually lose some of their genetic controls, which normally limit their multiplication (cell division). When this happens, cells may proliferate, leading to an abnormal architectural pattern of the epithelial cells. This over-proliferation of cells is termed hyperplasia. Sometimes these proliferating cells begin to appear abnormal and to look different from one another. They are now described as "atypical." As other more normal cells continue to cycle, die and break down, these atypical cells can move in, spread out, and accumulate. This extensive overgrowth and accumulation of atypical cells is called atypical hyperplasia.

Medically Reviewed by a Doctor on 7/13/2017

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