Breast Cysts During Lactation: Causes and Resolution

Mammary cyst during lactation

Hello, last year, less than a month postpartum, I had a breast ultrasound due to discomfort from engorgement.
The doctor mentioned that there were two cysts, each less than one centimeter.
The doctor said to wait and see if they would resolve after I stopped breastfeeding.
During this year's follow-up (without breastfeeding), they were no longer present.
Could these cysts have been caused by milk duct obstruction? If so, do they appear the same on ultrasound as typical cysts? I checked my health records, and it states "single cyst in the left breast," is this the same as a fibrocystic cyst? Is it common for them to resolve on their own? Thank you!

Xiao Wu, 30~39 year old female. Ask Date: 2019/10/27

Dr. Chen Jiaming reply Surgery

During the breastfeeding period, the breast tissue secretes milk from the peripheral lobules, which is then transported through the ducts to the nipple.
If these ducts become completely obstructed, it can lead to mastitis (swelling and pain).
Occasionally, small cysts may appear within the ducts, which are referred to by physicians as "cysts." Regardless of the stage, the cysts identified by ultrasound are classified as a type of "morphology," so they are all similar.
The occurrence of cysts during breastfeeding is mostly temporary, similar to how you may track something that has disappeared.
In contrast, fibrocystic changes during non-breastfeeding periods are often related to the menstrual cycle, fluctuating in response (peaking before menstruation, making them more prone to swelling and pain, and gradually decreasing after menstruation).
Generally, these changes are observed to resolve naturally after reaching menopause (defined as one year after the last menstrual period).

Reply Date: 2019/10/27

More Info

Breast cysts, particularly during lactation, are a common concern for many women. Understanding their causes, characteristics, and potential resolutions can help alleviate anxiety and promote better breast health.

Causes of Breast Cysts During Lactation
Breast cysts are fluid-filled sacs that can develop in the breast tissue. During lactation, hormonal changes, particularly fluctuations in estrogen and progesterone, can lead to the formation of these cysts. When a woman is breastfeeding, the milk-producing glands can become engorged, and if the milk ducts become blocked, fluid may accumulate, resulting in cyst formation. This is often referred to as a milk duct obstruction.

In your case, the ultrasound revealed two small cysts (less than one centimeter) shortly after giving birth, which is consistent with the physiological changes that occur during lactation. The fact that these cysts resolved after you stopped breastfeeding suggests that they were likely related to the temporary changes in your breast tissue during that period.

Characteristics of Breast Cysts
On ultrasound, breast cysts typically appear as well-defined, anechoic (dark) areas, indicating fluid content. They can vary in size and may be simple (just fluid) or complex (containing solid components). Simple cysts are generally benign and often resolve on their own, especially after hormonal changes stabilize post-lactation.

You mentioned that the health record indicated a "single cyst" on the left breast, which aligns with the characteristics of a breast cyst. Fibrocystic changes, which are common in women of reproductive age, can also present with similar ultrasound findings. These changes are often benign and can include both cysts and fibrous tissue.

Resolution of Breast Cysts
It is not uncommon for breast cysts to resolve spontaneously, especially in the context of hormonal fluctuations associated with lactation. Many women experience cysts that appear during breastfeeding but disappear after they stop nursing. This is likely due to the normalization of hormone levels and the reduction of milk production, which alleviates any blockages in the milk ducts.

In your case, the cysts you had were no longer present during your follow-up examination after you ceased breastfeeding, indicating that they were likely transient and related to your lactation period.

Conclusion
In summary, the cysts you experienced were likely caused by milk duct obstruction due to engorgement during lactation. They are typically benign and can resolve on their own after breastfeeding ends. If you notice any new lumps, persistent pain, or changes in your breast tissue in the future, it is essential to consult a healthcare provider for further evaluation. Regular breast self-exams and routine check-ups can help monitor breast health and catch any potential issues early.
If you have any further concerns or questions about breast health, do not hesitate to reach out to a healthcare professional for personalized advice and support.

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