If you have a high risk of breast cancer, you may require frequent monitoring or additional testing. There aren’t any other life-threatening complications of breast cysts. They can sometimes become infected, or can become large, tense and painful and require aspiration.
There are three types of breast cysts:
- Simple breast cyst: Filled entirely with fluid, simple cysts are always noncancerous. There’s no solid area in the cyst and the cyst wall is smooth. They make up about 90% of all breast cysts.
- Complex breast cyst: This type of cyst, which has a mix of fluid and solid components, may be breast cancer in up to 20% of cases. Your provider typically biopsies the tissue, which means they remove part of your breast tissue and send it to a lab for analysis.
- Complicated breast cyst: A complicated cyst is fluid-filled, but may have some cloudiness to the fluid, or the borders may be somewhat irregular. Sometimes, these are aspirated with a needle biopsy and then the tissue is sent for analysis. Other times, a provider may recommend a follow-up appointment in six months because there’s just a small chance (less than 2%) of it being cancerous.
Breast cysts can also be microcysts or macrocysts. Most breast tissue contains microcysts, which are very tiny and may be seen by ultrasound or even just under a microscope. Macrocysts are larger and can often be felt.
The exact cause of breast cysts is still unknown. Experts believe natural hormonal fluctuations may cause them to form. Breast cysts don’t usually develop after menopause when estrogen levels taper off. It’s also thought to be a part of the normal life cycle of a breast — when the milk-producing glandular tissue shrinks (involution) and fluid becomes trapped.
Breast cysts may be found in one or both breasts. Signs and symptoms of a breast cyst include:
- A smooth, easily movable round or oval lump that may have smooth edges — which typically, though not always, indicates it’s benign
- Nipple discharge that may be clear, yellow, straw colored or dark brown
- Breast pain or tenderness in the area of the breast lump
- An increase in breast lump size and breast tenderness just before your period
- A decrease in breast lump size and resolution of other symptoms after your period
Needed tests may include:
- Mammography. Large cysts and clusters of small cysts can usually be seen with mammography. But microcysts can be difficult or impossible to see on a mammogram.
- Breast ultrasound. This test can help your doctor determine whether a breast lump is fluid filled or solid. A fluid-filled area usually indicates a breast cyst. A solid-appearing mass most likely is a noncancerous lump, such as a fibroadenoma, but solid lumps also could be breast cancer.
Your doctor may recommend a biopsy to further evaluate a mass that appears solid. If your doctor can easily feel a breast lump, he or she may skip imaging tests and perform fine-needle aspiration to drain the fluid and collapse the cyst.
During a fine-needle aspiration, your doctor inserts a thin needle into the breast lump and attempts to withdraw (aspirate) fluid. Often, fine-needle aspiration is done using ultrasound to guide accurate placement of the needle. If fluid comes out and the breast lump goes away, your doctor can make a breast cyst diagnosis immediately.
- If the fluid is not bloody and has a straw-colored appearance and the breast lump disappears, you need no further testing or treatment.
- If the fluid appears bloody or the breast lump doesn’t disappear, your doctor may send a sample of the fluid for lab testing and refer you to a breast surgeon or to a radiologist — a doctor trained to perform imaging exams and procedures — for follow-up.
- If no fluid is withdrawn, your doctor will likely recommend an imaging test, such as a diagnostic mammogram or ultrasound. The lack of fluid or a breast lump that doesn’t disappear after aspiration suggests that the breast lump — or at least a portion of it — is solid. A sample of the tissue may be collected to check for cancer.