Breast cysts are round or oval structures filled with fluid. About 25% of all breast masses turn out to be cysts. Most breast cysts are benign and do not increase your risk of breast cancer.
They can be very tiny, or they can be large enough to feel through the skin or see on an imaging test (a grossly evident cyst, or gross cyst). Many cysts fall somewhere in between.
Cysts can occur at any age, but they’re most common for women in their 40s. In more than half of cases, women develop multiple cysts, either all at once or over a period of time. If a cyst is large enough to be felt, it’s usually round and fairly movable under the skin. Cysts also can cause pain, tenderness, or lumpiness in the breast. Those symptoms may worsen and get better at different points in the menstrual cycle.
Diagnosis of cysts
When diagnosing a cyst, doctors want to figure out whether it is simple, complex, or somewhere in between (complicated). Ultrasound imaging can be used to determine this.
- Simple cysts have smooth, thin, regularly shaped walls and are completely filled with fluid. The sound waves sent out by the ultrasound test pass right through them, indicating there are no solid areas. Simple cysts are always benign.
- Complex cysts have irregular or scalloped borders, thick walls, and some evidence of solid areas and/or debris in the fluid. These solid areas echo back the sound waves from the ultrasound. A complex cyst is sometimes aspirated, or drained with a fine needle, so that the fluid inside can be tested. If blood or any unusual cells are present, further testing may be needed to rule out breast cancer.
- Complicated cysts are “in between” simple and complex. Although they share most of the features of simple cysts, they tend to have some debris inside them and echo back some of the ultrasound waves. However, they don’t have the thick walls or obvious solid components that a complex cyst has.
Be aware that many radiologists (physicians who perform and read the imaging studies) use the terms “complicated” and “complex” interchangeably. So if you see either term, ask for specific information about the features of the cyst. Most of these cysts turn out to be benign.
With complex cysts, doctors want to rule out any possibility that that the solid areas contain cancer cells. In such cases biopsy may be needed (more details below).
Treatment and follow-up
For simple cysts, no treatment is needed unless the cyst is especially large, uncomfortable, or painful. The cyst can be then be drained with a fine needle. If the cyst comes back, it may be evaluated again with mammogram and ultrasound, and it can be drained again. Most women with simple cysts go back to routine breast cancer screening.
For complicated or complex cysts, the follow-up plan is generally the same, once imaging confirms that the growth is a cyst. In select cases, your doctor might recommend fine needle aspiration to drain it and examine the fluid inside. Or he or she may ask to see you every 6-12 months for 1-2 years to check on the cyst. Typically, you would have a clinical breast exam and ultrasound, with or without mammography.
If at any point your doctor feels that the cyst has suspicious features suggesting it could actually be a breast cancer, he or she can order a biopsy to make sure any solid parts inside the cyst are benign. Your doctor may use ultrasound to guide a core needle into the cyst and remove tissue samples for examination under a microscope. Rarely, he or she may need to remove the cyst (excisional biopsy).
Naturally, women get concerned when they hear the terms “complex” or “complicated,” but most cysts check out okay. “I often tell women to think about what would happen if they left out a glass of water for months and then came back to it; the water would be cloudy and have some dirt in it,” notes Dr. Stolier. “A similar process can occur with the fluid in a cyst over time.”
If you have multiple cysts or you develop new cysts frequently, you might consider being managed by a breast specialist. Having cysts along with other breast cancer risk factors, such as a strong family history, leads many women to do this. Even though cysts do not increase breast cancer risk, seeing a breast specialist can be reassuring.