Breast Lumps
Various new breast lumps may be detected by pregnant women due to the vast, normal amount of new tissue and duct growth that occurs to prepare for milk production.
Fortunately, most lumps detected during pregnancy are benign, and are usually fibroadenomas, lactating adenomas, fluid-filled cysts, or galactoceles.
However, any new lumps should be brought to the attention of an HCP. This is not due to the likelihood of malignancy, but to avoid a delay in diagnosis in the unlikely event that it could be.
Further, ultrasound can be used to confirm a benign finding and allow peace of mind for women who feel significant stress and anxiety due to the existence of a new lump.
Women should be very familiar with their breasts prior to and during pregnancy so any new lumps can be identified and assessed quickly. Women who have any questions or concerns should talk to their HCP.
Background
Pregnant women tend to notice numerous new lumps in their breasts due to fast tissue growth and milk production.
This can cause some women immediate stress, as lumps are usually not distinguishable by touch alone. However, most “true lumps” found during pregnancy are benign (noncancerous) (estimated up to 80%).
Benign lumps are either fibroadenomas, lactating adenomas, fluid-filled cysts, or galactoceles. Of these, lactating adenoma and fibroadenoma are the two most prevalent. After delivery and breastfeeding, many of these go away without treatment (after lump type has been confirmed).
The most important thing a woman can do is learn and remember what her breasts felt like before pregnancy to get a baseline of “normal”. Any new lumps that last two weeks or longer should be evaluated by an HCP. An HCP can also help differentiate between a true lump and a clogged milk duct during the postpartum period.
An HCP will inquire about the date of appearance of the lump, as well as individual patient history, previous lumps, and familial history.
In addition, breasts should be examined by an HCP at the very beginning of pregnancy as well. A previously palpable lump that was not assessed prior to pregnancy can be concealed by enlarging breast tissue or may increase in size during pregnancy.
Management
Unlike other sections of this site, management is listed first. This is because ultrasound, biopsy, and/or surgery may come before the actual type of lump is identified. Pregnancy is also is a very specific time frame in which lumps are investigated more aggressively because of the difficulty in determining the type of lump by imaging alone.
Ultrasound is used as the first-line imaging technique. It enables accurate diagnosis of simple cystic lesions and sometimes helps to confirm the lump is just normal tissue.
However, due to the growth of new tissue and other physiological changes of the breasts during pregnancy, ultrasound examination of the breasts can be challenging.
Certain changes can hide the presence of potential malignant lumps, and inflammation and new normal growth can be mistaken for malignancies. It is also possible that due to increased breast density, that HCPs may not find ultrasound helpful at all, and other imaging techniques may be required.
A 4-view mammography may be performed, in which the fetus is exposed to a negligible amount of radiation. Some research indicates that mammography is less effective during pregnancy due to increased breast density, but the benefits may outweigh any radiation risk.
If diagnosis is still unsure after various imaging methods, a biopsy is recommended. Breast biopsies are safe, commonly done during pregnancy, and do not necessarily indicate the HCP suspects cancer. Biopsies are performed to confirm benign growths as well and are the most reliable method for diagnosing solid masses.
Lactating Adenoma
A lactating adenoma is a very common benign, mobile (moves), painless, soft “mass” about 3 centimeters (cm) or less in size caused by physical breasts changes during pregnancy. Although it can occur at any time, it is most common during the third trimester and lactation, and regresses when breastfeeding is stopped.
Lactating adenoma can be large, firm, and painful in some cases, which is why diagnostic testing is usually recommended to distinguish it from other types of lumps (even without symptoms). Ultrasound is used first, followed by MRI (no radiation) or biopsy to confirm diagnosis.
No treatment is necessary in most confirmed cases, but if the lump continues to enlarge or causes severe pain, surgical removal may be required. Surgery is highly effective and generally does not interfere with pregnancy or continued attempts to breastfeed.
Fibroadenoma
Fibroadenomas are benign solid, firm, mobile, painless lumps between 1 cm and 20 cm in size that develop in the lobules of the breast, most commonly in women in their 20s and 30s. Although their cause is unknown, estrogen is likely responsible.
In non-pregnant women, approximately 0.5% to 2% of these lumps will grow rapidly; during pregnancy, they can grow even faster due to high concentrations of estrogen, progesterone, and prolactin that promote ductal growth. Women with a history of taking oral contraceptives before 20 years of age tend to suffer from fibroadenoma at higher rates than the general population. Women may even have one prior to pregnancy but are unaware of it until it grows during pregnancy.
Because fibroadenomas can grow quickly, be quite large, slightly deformed, and can cause bloody nipple discharge (rarely), they can raise suspicion of malignancy more frequently than other types of lumps, and are often biopsied.
Fibroadenomas can go away on their own without treatment, usually after breastfeeding is stopped, but the probability of this is debated. Watchful waiting is recommended if it persists, based on patient history. If the fibroadenoma begins to cause excessive pain or grows, surgical removal is recommended.
Galactocele
Galactoceles are the most common benign mass in the breastfeeding period and have been reported to mimic malignancies.
A galactocele is a cyst containing milk, which occurs when a milk duct becomes obstructed generally due to inflammation. It can occur during the third trimester but usually occurs after delivery and during breastfeeding. It can be a single mass or multiple, that is/are soft and painless.
Ultrasound and fine-needle aspiration biopsy are the most common techniques for treating galactoceles. A biopsy has the added benefit of also treating the cyst at the same time by removing the milk.
Postpartum (Awareness)
Whether or not a postpartum woman is breastfeeding, she still needs to pay attention to the potential formation of new or unusual breast lumps, even up to ten years after delivery.
A literature review of postpartum breast cancer published in February 2021 found that "breast cancers that occur in young women up to 5 to 10 years' postpartum are associated with an increased risk for metastasis and death compared with breast cancers diagnosed in young, premenopausal women during or outside pregnancy." A primary factor that could lead to a more aggressive cancer is a delay in diagnosis due to physical postpartum changes of the breasts.
Breastfeeding has been shown to be protective against breast cancer, likely due to a delay in a "return to normal" (known as involution). The relative risk of breast cancer may decrease by 4.3% for every 12 months of breastfeeding. Risk reductions of 33% have been seen in women who have consistently breastfed for up to 2 years.
Action
The most important thing a woman can do is learn and remember what her breasts felt like before pregnancy to get a baseline of “normal”. Any new lumps that last two weeks or longer should be evaluated by an HCP, whether during pregnancy or in the postpartum period.
An HCP can also help differentiate between a true lump and a clogged milk duct during the postpartum period.
Women should also consider sharing and submitting their experience below regarding breast lumps during pregnancy.
Resources
Possible Breast Changes During and After Pregnancy (U.K. National Health Service)
Breast Self Exam (Breastcancer.org)
Screening for Breast Cancer during Pregnancy (Breastcancer.org)