A galactocele is a benign milk retention cyst that forms in the breast when milk becomes trapped behind a blocked milk duct. It is the most commonly diagnosed benign breast mass in lactating patients. Galactoceles most often appear after breastfeeding ends, though they can also develop during the third trimester of pregnancy or while actively nursing.
How a Galactocele Forms
Your breast contains a network of ducts that carry milk from the glands to the nipple. When one of these ducts becomes persistently blocked, milk accumulates behind the obstruction and forms a fluid-filled cyst. Over time, the trapped milk may thicken as water is reabsorbed, leaving behind a mixture of fat, protein, and sometimes crystallized components. The cyst itself is enclosed and separate from the surrounding breast tissue, which is why it feels like a distinct lump.
The blockage can happen for a number of reasons: pressure from a bra, changes in nursing patterns, or the natural process of milk drying up after weaning. The hormonal shifts that occur when you stop breastfeeding can cause ducts to narrow while residual milk is still present, which is why most galactoceles show up after lactation ends rather than during peak milk production.
What a Galactocele Feels Like
A galactocele typically presents as a moderately firm, smooth, round mass in the breast. It tends to increase in size gradually or sometimes rapidly over time. One distinctive feature: the lump may fluctuate in size throughout the day, temporarily shrinking after breastfeeding or pumping as surrounding pressure changes. It is usually painless, though larger cysts can feel uncomfortable or create a sensation of fullness.
Most galactoceles are located in the central or subareolar area of the breast, near the nipple, since that’s where the major ducts converge. They can range from small, barely noticeable lumps to cysts several centimeters across. Finding any new breast lump is understandably alarming, but galactoceles are not cancerous and do not increase your risk of breast cancer.
How It’s Diagnosed
Ultrasound is typically the first imaging tool used, especially in younger or breastfeeding patients. A galactocele often appears as a well-defined, oval or round mass. Its appearance on imaging can vary depending on how much fat versus fluid the cyst contains, which sometimes makes it tricky to distinguish from other breast masses on imaging alone.
The most definitive diagnostic step is needle aspiration. A thin needle is inserted into the cyst, and the fluid drawn out. A galactocele produces a thick, milky or creamy aspirate, which is unmistakable and confirms the diagnosis on the spot. This procedure is both diagnostic and therapeutic: draining the cyst relieves symptoms and confirms what it is in a single step.
Galactocele vs. Other Breast Lumps
Several types of breast lumps can appear during pregnancy and breastfeeding, so it helps to understand how a galactocele compares to the more common ones:
- Breast abscess: An abscess is a pocket of infection. It causes redness, warmth, significant pain, and often fever. A galactocele is typically painless and not associated with skin changes or systemic symptoms, unless it becomes secondarily infected.
- Fibroadenoma: These are solid, rubbery lumps made of breast tissue. They feel firm and movable, similar to a galactocele, but they won’t fluctuate in size with feeding and won’t produce milky fluid on aspiration.
- Lactating adenoma: A benign solid tumor that can enlarge during pregnancy and breastfeeding due to hormonal stimulation. Unlike a galactocele, it is a solid mass rather than a fluid-filled cyst, and this difference is visible on ultrasound.
Treatment Options
Many galactoceles resolve on their own once breastfeeding fully stops and residual milk is reabsorbed by the body. Small, painless cysts that aren’t bothering you may not need any treatment at all.
For symptomatic galactoceles, drainage is recommended. This relieves discomfort, confirms the diagnosis, and reduces the size of the mass so it doesn’t interfere with breastfeeding if you’re still nursing. Simple needle aspiration works well as a first step, but there’s a catch: aspiration alone often results in incomplete drainage or the cyst refilling. Repeated needle aspirations carry a risk of introducing bacteria into a previously sterile cyst, potentially converting it into an infected galactocele. For this reason, placement of a small drain is sometimes preferred over repeated needle passes.
If a galactocele becomes infected, it requires both drainage and antibiotics. Signs of infection include new pain, redness, warmth over the lump, or fever. Surgical removal of the cyst is rarely necessary but may be considered for galactoceles that keep recurring despite drainage or that are very large.
Breastfeeding With a Galactocele
A galactocele does not require you to stop breastfeeding. You can continue nursing from the affected breast. In fact, if the cyst is large enough to create a “mass effect,” where the lump distorts the breast shape and makes it harder for your baby to latch, draining it can actually improve the breastfeeding experience. After aspiration or drain placement, breastfeeding from that breast can continue as normal.
The cyst itself doesn’t contaminate your milk supply or pose any risk to your baby. It’s simply milk that took a wrong turn and got trapped. Your remaining ducts continue to function, and milk production from the rest of the breast is unaffected.