During breastfeeding, you may find a lump in your breast and be concerned about what it means. In people who aren’t breastfeeding, lumps can be possible signs of breast cancer. However, during breastfeeding, lumps and other breast changes are most often totally normal. Additionally, several benign (noncancerous) breast conditions can cause breast lumps.

Breast cancer is extremely uncommon during breastfeeding. Just 1 in 3,000 women will develop breast cancer while breastfeeding, according to a 2023 study in the International Journal of Surgery Case Reports. Breast cancer is uncommon during breastfeeding because most people who are breastfeeding are too young to be at high risk — just 5 percent to 7 percent of breast cancer cases occur in women under 40, the researchers reported.

Cysts During Breastfeeding

If you find a lump in your breast during breastfeeding, it could be a cyst called a galactocele. Usually painless, these milk-filled cysts develop when a blocked milk duct causes milk to build up in the breast. Galactoceles are diagnosed with ultrasound and can resolve on their own after breastfeeding ends, but if necessary, the blockage can be drained using a needle or removed with surgery.

Mastitis

Lumps in the breast can also be a sign of inflammation in the breast known as mastitis. Hard lumps or lumps that cause breast pain are often a symptom of this condition. The inflammation also can give you flu-like symptoms, such as achiness and exhaustion, and you may run a fever. Your breasts may swell, and the affected area on your breast may also redden or darken, although skin changes don’t always occur.

Mastitis is usually treated with ibuprofen, warm compresses, and ice packs. If the symptoms continue, your doctor may prescribe antibiotics to treat the breast infection.

In some mastitis cases, a pocket full of pus called an abscess can form. Just like a cyst, a breast abscess can be drained using a needle.

Don’t stop breastfeeding if you have mastitis. Ensuring a consistent milk flow actually helps to clear the infection and promote proper drainage, and healthy babies aren’t at risk from drinking breast milk during a mastitis episode. If you have extra milk after feeding, you can try expressing it by hand or with a breast pump.

Massage also helps. Massaging the breast with strokes toward the nipple can ease lactation (production and secretion of milk), while stroking away from the nipple and toward the armpit encourages lymphatic drainage.

Mammograms While Breastfeeding

Redness or darkening, bruising, and swelling in the affected breast are common symptoms of mastitis, but they can also be signs of a rare form of breast cancer called inflammatory breast cancer (IBC). This cancer usually develops within the milk ducts and then spreads throughout the breast. IBC leads to quick changes in the breast’s appearance, usually over a period of just a few weeks.

IBC is rare, making up 1 percent to 5 percent of breast cancer cases. If you’re breastfeeding, it’s much more likely that your symptoms are caused by mastitis. However, if breast discoloration and swelling persist after antibiotic treatment for mastitis ends, your health care provider may suggest getting a mammogram to take a further look at your breast tissue.

Reading a mammogram of breasts that are producing milk can be difficult, but it’s still possible. Breastfeeding or pumping right before the mammogram can help empty your breasts to produce a clearer X-ray. Depending on what the mammogram shows, your doctor may also order a biopsy to get more details about the lump. A biopsy entails removing a small tissue sample for examination under a microscope.

Mammogram X-rays and biopsies don’t affect the milk supply, so it’s safe to feed your baby after these procedures.

Talk With Others Who Understand

MyBCTeam is the social network for people with breast cancer and their loved ones. On MyBCTeam, more than 65,000 members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Have you experienced breast lumps during breastfeeding? What other breast symptoms, if any, did you have? Share your experiences in the comments below, or start a conversation by posting on MyBCTeam.