A galactocele is a benign, milk-filled cyst that forms in the breast when a milk duct becomes blocked. It occurs almost exclusively in people who are currently breastfeeding or have recently stopped. The trapped milk accumulates behind the blockage, creating a round, cyst-like lump that can range from barely noticeable to larger than 10 cm across.
How a Galactocele Forms
Three things need to happen simultaneously for a galactocele to develop: the breast tissue must be in a milk-producing state, the hormone prolactin must be actively stimulating milk production, and a milk duct must become blocked. When all three conditions are present, milk backs up behind the obstruction, and the duct balloons outward into a fluid-filled cyst.
Several factors can trigger that initial duct blockage:
- Breastfeeding technique issues, such as a poor latch that leaves parts of the breast inadequately drained
- Decreased feeding frequency, including sudden changes in nursing schedules or abrupt weaning
- Breast trauma, even mild trauma from aggressively squeezing the nipple to clear a plugged duct
- Inflammation from prior infection or tissue irritation
- Nipple abnormalities that narrow the duct opening
- Rarely, an underlying tumor pressing on a duct from outside
That last point is uncommon, but it’s one reason any new breast lump deserves evaluation even if you suspect it’s “just” a clogged duct.
What a Galactocele Feels Like
Most galactoceles present as a smooth, round, movable lump in the breast. They tend to feel firm but not rock-hard, and they’re typically painless or only mildly tender. Unlike a breast infection or abscess, a galactocele usually doesn’t come with redness, warmth, swelling of the surrounding skin, or fever. It simply feels like a discrete lump sitting within the breast tissue.
Size varies widely. Some galactoceles are small enough that you only notice them during a self-exam, while others grow large enough to be visible or to cause a noticeable change in breast shape. They most commonly appear during active breastfeeding or within the first several months after weaning, when milk production is tapering but hasn’t fully stopped.
How It Differs From Other Breast Lumps
Finding a lump while breastfeeding is understandably alarming, but not every lump is the same. A plugged duct typically resolves within a day or two with continued nursing and massage. A galactocele persists because the milk is sealed inside a cyst wall, not just temporarily stuck. A breast abscess, on the other hand, involves infection: you’d expect significant pain, redness, heat over the area, and often a fever. Galactoceles are not infected and don’t cause systemic symptoms like fever or chills.
Because galactoceles are completely benign, they carry no increased risk of breast cancer. However, on imaging they can sometimes mimic other types of breast masses, which is why doctors typically confirm the diagnosis with ultrasound or, if needed, by withdrawing a small sample of the cyst’s contents.
How Galactoceles Are Diagnosed
Ultrasound is the first-line imaging tool, especially for breastfeeding patients. On ultrasound, a galactocele typically appears as a well-defined, oval or round cyst. One characteristic finding is a visible fat-fluid level inside the cyst, where the fatty portion of the milk floats above the watery portion. This layered appearance is a strong clue that the mass is milk-filled rather than solid.
If the ultrasound appearance is straightforward, that may be enough for diagnosis. When there’s any uncertainty, a needle aspiration can confirm things quickly. A thin needle is inserted into the cyst, and the fluid drawn out is examined. Milky or creamy fluid is essentially diagnostic. This procedure also doubles as treatment, since draining the cyst often resolves the lump entirely.
Treatment and What to Expect
Many galactoceles resolve on their own, particularly once breastfeeding ends and prolactin levels drop. As the breast stops producing milk, the cyst gradually shrinks and the body reabsorbs the fluid. For small, painless galactoceles, watchful waiting is a perfectly reasonable approach.
If the cyst is large, uncomfortable, or cosmetically bothersome, needle aspiration is the standard first step. The procedure is quick, performed in an office setting, and usually takes just a few minutes. The main drawback is that galactoceles can refill after aspiration, especially if you’re still breastfeeding and the underlying duct obstruction persists. Some people need the cyst drained more than once.
Surgical removal is rarely necessary. It’s generally reserved for galactoceles that keep recurring despite repeated drainage, or for the uncommon cases where imaging can’t rule out a different type of mass. Surgery is a minor procedure but does carry the usual risks of any breast operation, including potential effects on milk ducts if you plan to breastfeed again in the future.
Breastfeeding With a Galactocele
A galactocele does not mean you need to stop breastfeeding. The cyst itself is simply trapped milk, and continuing to nurse from the affected breast is generally safe. In fact, frequent and effective breast drainage may help prevent additional cysts from forming. Ensuring a good latch, nursing on a consistent schedule, and avoiding abrupt changes in feeding frequency all reduce the risk of further duct blockages.
That said, a large galactocele can sometimes make latching difficult if it distorts the shape of the breast or nipple. In those cases, draining the cyst can restore normal anatomy and make breastfeeding more comfortable. Working with a lactation consultant can help address any underlying latch or positioning issues that may have contributed to the blockage in the first place.
Long-Term Outlook
Galactoceles are benign and carry an excellent prognosis. Most disappear within weeks to months after breastfeeding ends. In rare cases, a galactocele that isn’t drained or reabsorbed can undergo calcification over time, meaning the milk solids harden and leave a firm, calcium-dense mass in the breast. These calcified galactoceles are still benign, but they can look suspicious on a future mammogram and may require a biopsy to confirm they aren’t something more concerning. If you’ve ever had a galactocele, mentioning it to the radiologist before a mammogram can help avoid unnecessary worry down the line.