ConditionWomen's & pregnancy health
Breast Cyst
A breast cyst is a round, fluid-filled sac in the breast tissue. Cysts are very common, especially between 35 and 50, and are almost always benign. They feel smooth and movable, like a grape or water balloon, and may become larger and tender before a period. An ultrasound confirms a simple cyst, which needs no treatment unless it is painful. Any new breast lump should still be checked by a doctor, because a lump cannot be confirmed as a cyst by feel alone.
Also called: Breast cysts, simple breast cyst, complicated cyst, fibrocystic breast changes
At a glance
- What it is
- A fluid-filled sac in the breast.
- Who gets it
- Most often women aged 35 to 50 and those on hormone therapy after menopause.
- Feel
- Smooth, round, movable; may be tender; can change with the cycle.
- Diagnosis
- Ultrasound; mammogram in women over 30 to 40.
- Treatment
- None for simple cysts; needle aspiration for painful cysts.
When to get help
See a doctor within a day or two
- A red, hot, swollen, painful breast with fever (possible infection or abscess)
Book a routine appointment
- Any new breast lump, even if you have had cysts before
- A lump that is hard, fixed, or irregular, or that does not change with your cycle
- Skin dimpling, an inverted nipple, or bloody or clear discharge from one nipple
- A cyst that keeps refilling after drainage, or has bloody fluid
- A new lump after menopause
Usually safe to manage at home
- A known simple cyst, confirmed on ultrasound, that is mildly tender before periods
How breast cysts form
Breast tissue contains milk-producing lobules and ducts. Hormone changes through the menstrual cycle can cause fluid to build up in the lobules faster than it drains, forming a sac. Cysts can be tiny (microcysts) or several centimeters across (macrocysts). They often appear and disappear with the cycle and are part of the wider pattern of fibrocystic breast changes.
Symptoms
- a smooth, round or oval lump with clear edges
- the lump moves under the skin
- it may feel soft, or firm if tense with fluid
- tenderness or aching, often worse in the week before a period
- a lump that gets bigger before a period and smaller after
- one or many, in one or both breasts
Many cysts cause no symptoms and are found on mammograms.
Types of breast cyst
| Type | Ultrasound appearance | What it means |
|---|---|---|
| Simple cyst | Smooth, thin wall, completely fluid-filled | Benign; no follow-up needed |
| Complicated cyst | Fluid with internal echoes or debris | Almost always benign; may have a short-term follow-up scan or aspiration |
| Complex cystic and solid mass | Thick walls or a solid part | Needs biopsy to rule out cancer |
Breast cyst vs solid lump
| Cyst | Fibroadenoma | Breast cancer | |
|---|---|---|---|
| Content | Fluid | Solid | Solid |
| Feel | Smooth, round, may be tender | Rubbery, very mobile ("breast mouse") | Often hard, irregular, fixed |
| Age | 35 to 50 | 15 to 35 | Mostly over 50 |
| Cycle changes | Often | Sometimes | No |
You cannot reliably tell these apart by touch, which is why imaging is needed. See fibroadenoma and breast cancer.
Causes and risk factors
- hormonal fluctuation, especially estrogen
- age 35 to 50, approaching menopause
- hormone replacement therapy after menopause
- caffeine is often blamed, but evidence is weak
Cysts usually stop forming after menopause unless hormone therapy is used.
Diagnosis
- Clinical breast exam: your doctor feels the lump and checks the rest of both breasts and the armpits.
- Ultrasound: the main test. It shows whether a lump is fluid-filled or solid and identifies simple cysts.
- Mammogram: usually added for women over 30 to 40.
- Fine-needle aspiration: a thin needle drains the cyst. If the fluid is not bloody and the lump disappears completely, no further tests are needed.
- Biopsy: if there is a solid part, bloody fluid, or the lump remains after draining.
Treatment
- Simple cysts that cause no symptoms: no treatment. They often shrink or vanish on their own.
- Painful or large cysts: needle aspiration in the office gives quick relief. About a third come back, and can be drained again.
- Recurrent troublesome cysts: hormonal options are occasionally used. Surgery is rarely needed, usually only for recurrent cysts with bloody fluid or a suspicious finding.
- Pain relief: a supportive bra, warm or cool packs, and over-the-counter pain relievers such as ibuprofen, following the label dose.
Do breast cysts increase cancer risk?
Simple cysts do not increase breast cancer risk and do not turn into cancer. Very rarely, a cancer can grow inside a complex cyst, which is why complex cysts are biopsied. Continue routine breast screening as recommended for your age and risk.
Frequently asked questions
What does a breast cyst feel like?
A breast cyst usually feels like a smooth, round lump that moves easily under the skin, similar to a grape or a small water balloon. It may be soft or firm and is often tender, especially before a period.
Can a breast cyst turn into cancer?
Simple breast cysts do not turn into cancer and do not raise your risk. Complex cysts with solid areas are biopsied because rarely they contain cancer. A new lump should always be checked with an exam and imaging.
Do breast cysts go away on their own?
Many do, particularly as hormone levels change through the menstrual cycle or after menopause. Others stay the same size for years without causing problems. A painful cyst can be drained with a fine needle.
Is a painful breast lump more likely to be a cyst?
Pain is more common with cysts and infection than with cancer, but pain does not rule out cancer. Any new lump, painful or not, should be examined and imaged to confirm what it is.
Sources
This guide was written from current patient and clinical guidance, including:
- American College of Radiology: BI-RADS Atlas, breast ultrasound
- American Cancer Society: Fibrosis and simple cysts in the breast
- MedlinePlus: Breast lumps
- NHS: Breast cysts
- Mayo Clinic: Breast cysts